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Herran J, Prophet S, Jin Y, Valloppilly S, Kharel PR, Sellmyer DJ, Lukashev PV. Structural and magnetic properties of bulk Mn 2PtSn. J Phys Condens Matter 2018; 30:475801. [PMID: 30378571 DOI: 10.1088/1361-648x/aae652] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Interplay between structural and magnetic order parameters is one of the key mechanisms of tuning properties of materials intended for device applications in spintronics. Here, using density functional calculations, we study combined effects of tetragonal distortion and non-collinear magnetic order in Mn2PtSn. We show that this material has two energetically close energy minimums corresponding to tetragonal lattice. In one of these phases, Mn2PtSn exhibits ferrimagnetic order with nearly fully compensated total magnetic moment, while in the other phase that corresponds to the lowest energy, a non-collinear magnetic arrangement emerges, with very large canting angle of the Mn local magnetic moments. The non-collinear alignment is explained through the interplay of exchange couplings between nearest and next nearest neighbor Mn atoms. Results are compared with those reported in recent literature, both experimental and theoretical.
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Affiliation(s)
- J Herran
- Department of Chemistry and Biochemistry, University of Northern Iowa, Cedar Falls, IA 50614, United States of America
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Abstract
STEM images and elemental maps of Mn and Bi showing formation of complex core–shell and three-layer structure.
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Affiliation(s)
- P. Mukherjee
- Physics & Astronomy
- University of Nebraska
- Lincoln
- USA
- Nebraska Center for Materials and Nanoscience
| | - B. Balamurugan
- Physics & Astronomy
- University of Nebraska
- Lincoln
- USA
- Nebraska Center for Materials and Nanoscience
| | - J. E. Shield
- Nebraska Center for Materials and Nanoscience
- University of Nebraska
- Lincoln
- USA
- Mechanical & Materials Engineering
| | - D. J. Sellmyer
- Physics & Astronomy
- University of Nebraska
- Lincoln
- USA
- Nebraska Center for Materials and Nanoscience
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Huh Y, Kharel P, Nelson A, Shah VR, Pereiro J, Manchanda P, Kashyap A, Skomski R, Sellmyer DJ. Effect of Co substitution on the magnetic and electron-transport properties of Mn2PtSn. J Phys Condens Matter 2015; 27:076002. [PMID: 25629641 DOI: 10.1088/0953-8984/27/7/076002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The structural, magnetic and electron-transport properties of Mn(2)Pt(1-x)Co(x)Sn(x = 0, 0.3, 0.5, 0.7, 1) ribbons prepared by arc-melting and melt-spinning were investigated. The rapidly quenched alloys with x = 0 and 0.3 were found to crystallize in the inverse tetragonal structure, but the structure transformed into inverse cubic as x increased to 0.5. At room temperature, the samples are ferro or ferrimagnetic, and the Curie temperature increases by 225 K from 370 K for Mn(2)PtSn (x = 0) to 595 K for Mn(2)CoSn (x = 1). The measured anisotropy constants for the inverse-tetragonal alloys are on the order of 1 Merg cm(-3) at room temperature. The ribbons are moderately conducting with the room temperature resistivities being between 0.4 and 8.4 mΩ cm. Interestingly, the thermal coefficient of resistivity transforms from positive to negative and the magnetoresistance transforms from negative to positive as the value of x reaches 0.5.
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Affiliation(s)
- Y Huh
- Department of Physics, South Dakota State University, Brookings, SD, 57007, USA. Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE 68588, USA
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4
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Yu Y, Mukherjee P, Tian Y, Li XZ, Shield JE, Sellmyer DJ. Direct chemical synthesis of L1(0)-FePtAu nanoparticles with high coercivity. Nanoscale 2014; 6:12050-12055. [PMID: 25189100 DOI: 10.1039/c4nr02345e] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We report a facile synthesis of hard magnetic L10-FePtAu nanoparticles by coreduction of Fe(acac)3, Pt(acac)2 (acac = acetylacetonate) and gold acetate in oleylamine. In the current reaction condition, NP sizes are controlled to be 5.5 to 11.0 nm by changing the amount of Au doping. When the Au composition in the NPs is higher than 14%, the hard magnetic NPs are directly obtained without any annealing. The highest coercivity of 12.15 kOe at room temperature could be achieved for the NPs with 32% Au doping, which is much higher than the coercivities reported by the previous studies on solution-synthesized FePt nanoparticles. The reported one-pot synthesis of L10-FePtAu NPs may help to build superstrong magnets for magnetic or data-storage applications.
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Affiliation(s)
- Yongsheng Yu
- Nebraska Center for Materials and Nanoscience & Department of Physics and Astronomy, University of Nebraska-Lincoln, Lincoln, NE 68588, USA.
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Yu Y, Yang W, Sun X, Zhu W, Li XZ, Sellmyer DJ, Sun S. Monodisperse MPt (M = Fe, Co, Ni, Cu, Zn) nanoparticles prepared from a facile oleylamine reduction of metal salts. Nano Lett 2014; 14:2778-82. [PMID: 24690033 DOI: 10.1021/nl500776e] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
We report a simple, yet general, approach to monodisperse MPt (M = Fe, Co, Ni, Cu, Zn) nanoparticles (NPs) by coreduction of M(acac)2 and Pt(acac)2 (acac = acetylacetonate) with oleylamine at 300 °C. In the current reaction condition, oleylamine serves as the reducing agent, surfactant, and solvent. As an example, we describe in details the synthesis of 9.5 nm CoPt NPs with their compositions controlled from Co37Pt63 to Co69Pt31. These NPs show composition-dependent structural and magnetic properties. The unique oleylamine reduction process makes it possible to prepare MPt NPs with their physical properties and surface chemistry better rationalized for magnetic or catalytic applications.
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Affiliation(s)
- Yongsheng Yu
- Department of Chemistry, Brown University , Providence, Rhode Island 02912, United States
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Kharel P, Huh Y, Al-Aqtash N, Shah VR, Sabirianov RF, Skomski R, Sellmyer DJ. Structural and magnetic transitions in cubic Mn3Ga. J Phys Condens Matter 2014; 26:126001. [PMID: 24594858 DOI: 10.1088/0953-8984/26/12/126001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The structural, magnetic and electron-transport properties of cubic Mn3Ga have been investigated. The alloys prepared by arc melting and melt-spinning show an antiferromagnetic spin order at room temperature but undergo coupled structural and magnetic phase transitions at 600 and 800 K. First-principles calculations show that the observed magnetic properties are consistent with that of a cubic Mn3Ga crystallizing in the disordered Cu3Au-type structure. The samples exhibit metallic electron transport with a resistance minimum near 30 K, followed by a logarithmic upturn below the minimum. The observed anomaly in the low-temperature resistivity has been discussed as a consequence of electron scattering at the low-lying excitations of the structurally disordered Mn3Ga lattice.
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Affiliation(s)
- P Kharel
- Department of Physics, South Dakota State University, Brookings, SD 57007, USA. Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE 68588, USA
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Kumar P, Kashyap A, Balamurugan B, Shield JE, Sellmyer DJ, Skomski R. Permanent magnetism of intermetallic compounds between light and heavy transition-metal elements. J Phys Condens Matter 2014; 26:064209. [PMID: 24469225 DOI: 10.1088/0953-8984/26/6/064209] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
First-principle calculations are used to investigate the intrinsic magnetic properties of intermetallic alloys of the type XMn, where X is a 4d or 5d element and M is Fe or Co. Emphasis is on the hexagonal C14 Laves-phase 1:2 and 1:5 alloys, the latter crystallizing in the CaCu5 structure. These series are of interest in permanent magnetism from fundamental and practical viewpoints, respectively. In the former, the unit cells form a prototypical motif where a heavy atom with high spin-orbit coupling and magnetocrystalline anisotropy is surrounded by many somewhat smaller M atoms with high magnetization, and the latter are Laves-phase derivatives of renewed interest in permanent magnetism. Our DFT calculations predict magnetic moments, magnetizations and anisotropies, as well as formation energies. The results are analyzed across the 4d and 5d series, especially with respect to hybridization effects between 3d and 4d/5d bands.
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Balamurugan B, Das B, Zhang WY, Skomski R, Sellmyer DJ. Hf-Co and Zr-Co alloys for rare-earth-free permanent magnets. J Phys Condens Matter 2014; 26:064204. [PMID: 24468962 DOI: 10.1088/0953-8984/26/6/064204] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The structural and magnetic properties of nanostructured Co-rich transition-metal alloys, Co(100-x)TMx (TM = Hf, Zr and 10 ≤ x ≤ 18), were investigated. The alloys were prepared under non-equilibrium conditions using cluster-deposition and/or melt-spinning methods. The high-anisotropy HfCo7 and Zr2Co11 structures were formed for a rather broad composition region as compared to the equilibrium bulk phase diagrams, and exhibit high Curie temperatures of above 750 K. The composition, crystal structure, particle size, and easy-axis distribution were precisely controlled to achieve a substantial coercivity and magnetization in the nanostructured alloys. This translates into high energy products in the range of about 4.3-12.6 MGOe, which are comparable to those of alnico.
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Zhao X, Nguyen MC, Zhang WY, Wang CZ, Kramer MJ, Sellmyer DJ, Li XZ, Zhang F, Ke LQ, Antropov VP, Ho KM. Exploring the structural complexity of intermetallic compounds by an adaptive genetic algorithm. Phys Rev Lett 2014; 112:045502. [PMID: 24580466 DOI: 10.1103/physrevlett.112.045502] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/11/2013] [Indexed: 06/03/2023]
Abstract
Solving the crystal structures of novel phases with nanoscale dimensions resulting from rapid quenching is difficult due to disorder and competing polymorphic phases. Advances in computer speed and algorithm sophistication have now made it feasible to predict the crystal structure of an unknown phase without any assumptions on the Bravais lattice type, atom basis, or unit cell dimensions, providing a novel approach to aid experiments in exploring complex materials with nanoscale grains. This approach is demonstrated by solving a long-standing puzzle in the complex crystal structures of the orthorhombic, rhombohedral, and hexagonal polymorphs close to the Zr2Co11 intermetallic compound. From our calculations, we identified the hard magnetic phase and the origin of high coercivity in this compound, thus guiding further development of these materials for use as high performance permanent magnets without rare-earth elements.
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Affiliation(s)
- X Zhao
- Ames Laboratory-US Department of Energy, Ames, Iowa 50011, USA and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA
| | - M C Nguyen
- Ames Laboratory-US Department of Energy, Ames, Iowa 50011, USA and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA
| | - W Y Zhang
- Nebraska Center for Materials and Nanoscience and Department of Physics and Astronomy, University of Nebraska, Lincoln, Nebraska 68588, USA
| | - C Z Wang
- Ames Laboratory-US Department of Energy, Ames, Iowa 50011, USA and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA
| | - M J Kramer
- Ames Laboratory-US Department of Energy, Ames, Iowa 50011, USA and Department of Materials Science and Engineering, Iowa State University, Ames, Iowa 50011, USA
| | - D J Sellmyer
- Nebraska Center for Materials and Nanoscience and Department of Physics and Astronomy, University of Nebraska, Lincoln, Nebraska 68588, USA
| | - X Z Li
- Nebraska Center for Materials and Nanoscience and Department of Physics and Astronomy, University of Nebraska, Lincoln, Nebraska 68588, USA
| | - F Zhang
- Ames Laboratory-US Department of Energy, Ames, Iowa 50011, USA
| | - L Q Ke
- Ames Laboratory-US Department of Energy, Ames, Iowa 50011, USA
| | - V P Antropov
- Ames Laboratory-US Department of Energy, Ames, Iowa 50011, USA
| | - K M Ho
- Ames Laboratory-US Department of Energy, Ames, Iowa 50011, USA and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA
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Yue L, Al-Omari IA, Zhang W, Skomski R, Sellmyer DJ. Magnetic Domain Structure of Nanocrystalline Zr18-xHfxCo82 Ribbons: Effect of Hf. ACTA ACUST UNITED AC 2013. [DOI: 10.1557/opl.2013.1105] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
ABSTRACTThe effect of Hf on the permanent magnetism of nanocrystalline Zr18-xHfxCo82 ribbons (x = 0, 2, 4, and 6) was investigated by magnetic properties measurement and magnetic force microscopy (MFM). Emphasis is on the local magnetic domain structures in polycrystalline rapidly solidified Zr18-xHfxCo82 ribbons for four different samples with small fractions of Hf dopants (x ≤ 6). The investigation of the magnetic properties of the Zr18-xHfxCo82 ribbons revealed that all the samples under investigation are ferromagnetic at room temperature, and the corresponding MFM images show bright and dark contrast patterns with up-down magnetic domain structures. It is found that the saturation magnetization and the coercivity depend on Hf doping concentration x in the samples. For a sample with Hf concentration x = 4, the maximum energy product (BH)max value is 3.7 MGOe. The short magnetic correlation length of 131 nm and smallest root-mean-square phase shift value of 0.680 were observed for x = 4, which suggests the refinement of the magnetic domain structure due to weak intergranular exchange coupling in this sample. The above results indicate that suitable Hf addition is helpful for the magnetic domain structure refinement, the coecivity enhancement, and the energy-product improvement of this class of rare-earth-free nanocrystalline permanent-magnet materials.
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11
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Yu Y, Sun K, Tian Y, Li XZ, Kramer MJ, Sellmyer DJ, Shield JE, Sun S. One-pot synthesis of urchin-like FePd-Fe3O4 and their conversion into exchange-coupled L1(0)-FePd-Fe nanocomposite magnets. Nano Lett 2013; 13:4975-9. [PMID: 24041265 DOI: 10.1021/nl403043d] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
We report a one-pot synthesis of urchin-like FePd-Fe3O4 nanocomposites, spherical clusters of FePd nanoparticles (NPs) with spikes of Fe3O4 nanorods (NRs), via controlled thermal decomposition of Fe(CO)5 and reduction of Pd(acac)2. The FePd NPs with sizes between 6 and 9 nm self-aggregate into 60 nm superparticles (SPs), and Fe3O4 NRs grow on the surface of these SPs. Reductive annealing at 500 °C converts the FePd-Fe3O4 into exchange-coupled nanocomposites L1(0)-FePd-Fe with their Hc tunable from 0.8 to 2.6 kOe and Ms controlled from 90 to 190 emu/g. The work provides a general approach to L1(0)-FePd-Fe nanocomposite magnets for understanding exchange coupling at the nanoscale. The concept may be extended to other magnetic nanocomposite systems and may help to build superstrong magnets for magnetic applications.
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Affiliation(s)
- Yongsheng Yu
- Department of Chemistry, Brown University , Providence, Rhode Island 02912, United States
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12
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Wei XH, Zhou R, Balamurugan B, Skomski R, Zeng XC, Sellmyer DJ. Experimental and theoretical studies of hydroxyl-induced magnetism in TiO nanoclusters. Nanoscale 2012; 4:7704-7711. [PMID: 23132145 DOI: 10.1039/c2nr32858e] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
A main challenge in understanding the defect ferromagnetism in dilute magnetic oxides is the direct experimental verification of the presence of a particular kind of defect and distinguishing its magnetic contributions from other defects. The magnetic effect of hydroxyls on TiO nanoclusters has been studied by measuring the evolution of the magnetic moment as a function of moisture exposure time, which increases the hydroxyl concentration. Our combined experiment and density-functional theory (DFT) calculations show that as dissociative water adsorption transforms oxygen vacancies into hydroxyls, the magnetic moment shows a significant increase. DFT calculations show that the magnetic moment created by hydroxyls arises from 3d orbitals of neighboring Ti sites predominantly from the top and second monolayers. The two nonequivalent hydroxyls contribute differently to the magnetic moment, which decreases as the separation of hydroxyls increases. This work illustrates the essential interplay among defect structure, local structural relaxation, charge redistribution, and magnetism. The microscopic differentiation and clarification of the specific roles of each kind of intrinsic defect is critical for the future applications of dilute magnetic oxides in spintronic or other multifunctional materials.
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Affiliation(s)
- Xiao-hui Wei
- Department of Physics and Astronomy, University of Nebraska, Lincoln, Nebraska 68588, USA
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Wei X, Georgescu R, Ali N, Morjan I, George TA, Dumitrache F, Birjega R, Chipara M, Skomski R, Sellmyer DJ. On the synthesis and physical properties of iron doped SnO2 nanoparticles. J Nanosci Nanotechnol 2012; 12:9299-9301. [PMID: 23447992 DOI: 10.1166/jnn.2012.6784] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The synthesis of iron doped tin oxide by pulsed laser pyrolysis is reported. The as obtained nanoparticles have a dominant SnO2 phase (as revealed by Wide Angle X-ray Scattering), with particles of the order of 10 nm. The doping with iron or iron oxide triggers magnetic properties as confirmed by SQUID experiments. EDX measurements supported the presence of Fe while Wide Angle X-ray Scattering failed to sense any iron or iron-oxide phase. It is concluded that Fe is well dispersed within the tin-oxide nanoparticles. The coercitive field has a complex dependence on the Fe/Sn content suggesting that the magnetization is not controlled solely by the amount of Fe dispersed within the nanoparticles.
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Affiliation(s)
- X Wei
- Department of Physics and Astronomy, University of Nebraska, Lincoln, Nebraska 68588, USA
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Abstract
The electron transport properties of highly c-axis oriented MnBi thin films of various thicknesses have been investigated. Samples are metallic but the low temperature resistivity shows an unusual T(3) dependence. Transverse Hall effect measurements show that both the ordinary and anomalous Hall coefficients decrease with decreasing temperature below 300 K, but the ordinary Hall coefficient (R(0)) undergoes a sign reversal around 105 K, where the magnetic anisotropy also changes sign. Analysis of the Hall data for various samples shows that the anomalous Hall coefficient (R(s)) exhibits a strong ρ(2) dependence, where ρ is the longitudinal resistivity.
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Affiliation(s)
- P Kharel
- Nebraska Center for Materials and Nanoscience and Department of Physics and Astronomy, University of Nebraska, Lincoln, NE 68588, USA.
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Skomski R, Balamurugan B, Schubert E, Enders A, Sellmyer DJ. Length scales of interactions in magnetic, dielectric, and mechanical nanocomposites. ACTA ACUST UNITED AC 2011. [DOI: 10.1557/opl.2011.109] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
ABSTRACTIt is investigated how figures of merits of nanocomposites are affected by structural and interaction length scales. Aside from macroscopic effects without characteristic lengths scales and atomic-scale quantum-mechanical interactions there are nanoscale interactions that reflect a competition between different energy contributions. We consider three systems, namely dielectric media, carbon-black reinforced rubbers and magnetic composites. In all cases, it is relatively easy to determine effective materials constants, which do not involve specific length scales. Nucleation and breakdown phenomena tend to occur on a nanoscale and yield a logarithmic dependence of figures of merit on the macroscopic system size. Essential system-specific differences arise because figures of merits are generally nonlinear energy integrals. Furthermore, different physical interactions yield different length scales. For example, the interaction in magnetic hard-soft composites reflects the competition between relativistic anisotropy and nonrelativistic exchange interactions, but such hierarchies of interactions are more difficult to establish in mechanical polymer composites and dielectrics.
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All N, Chipara M, Balascuta S, Skomski R, Sellmyer DJ. Ferromagnetic resonance investigations on styrene-butadiene-styrene barium ferrite nanocomposites. J Nanosci Nanotechnol 2009; 9:4437-4441. [PMID: 19916470 DOI: 10.1166/jnn.2009.m73] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
FMR measurements on barium ferrite nanoparticles (with an average length of about 13 nm) dispersed within a block copolymer (styrene-butadiene-styrene) are reported. Resonance spectra have been successfully simulated by a convolution of a Dysonian line and a Lorentzian line. The temperature dependence of FMR spectra in the so called in-the-plane and out-of the-plane configurations is reported. The angular dependence of FMR spectra at room temperature is analyzed in detail and simulated within simple thermodynamic model that takes into account the competition between shape and magnetocrystalline anisotropies. FMR data revealed that the local magnetic field acting on uncoupled electronic spin is dominated by the magnetocrystalline contribution, which eventually includes surface effects. The strong connection between FMR spectra and hysteresis loop is demonstrated.
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Affiliation(s)
- N All
- School of Computing, Engineering and Physical Sciences, University of Central Lancashire, Preston PR1 2HE, UK
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Chipara M, Skomski R, Ali N, Hui D, Sellmyer DJ. Magnetic properties of barium ferrite dispersed within polystyrene-butadiene-styrene block copolymers. J Nanosci Nanotechnol 2009; 9:3678-3683. [PMID: 19504902 DOI: 10.1166/jnn.2009.ns50] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Magnetic properties of nanocomposite materials obtained by dispersing barium ferrite nanoparticles within polystyrene-butadiene-styrene block copolymer, in the temperature range, 300 to 500 K are reported. The temperature dependence of the magnetization at saturation, averaged uniaxial magnetocrystalline anisotropy, and coercive field of thick films are analyzed. A "matrix effect" was noticed within the glass transition range of the hard component (polystyrene) of the polymeric matrix. The reported modifications of the magnetic properties were assigned to the competition between the magnetic and mechanical reorientation of nanoparticles within the polymeric matrix. Such modifications were not observed in barium ferrite dispersed in cement.
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Affiliation(s)
- M Chipara
- Department of Physics and Geology, University of Texas-Pan American, Edinburg, TX 78541, USA
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Xu YF, Yan ML, Sellmyer DJ. FePt nanocluster films for high-density magnetic recording. J Nanosci Nanotechnol 2007; 7:206-24. [PMID: 17455485] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
High anisotropy L1(0) ordered FePt thin films are considered to have high potential for use as high areal density recording media, beyond 1 Tera bit/in2. In this paper, we review recent results on the synthesis and magnetic properties of L1(0) FePt nanocomposite films. Several fabrication methods have been developed to produce high-anisotropy FePt films: epitaxial and non-epitaxial growth of (001)-oriented FePt:X (X = Au, Ag, Cu, C, etc.) composite films that might be used for perpendicular media; monodispersed FePt nanocluster-assembled films grown with a gas-aggregation technique and having uniform cluster size and narrow size distribution; self-assembled FePt particles prepared with chemical synthesis by reduction/decomposition techniques, etc. The magnetic properties are controllable through variations in the nanocluster properties and nanostructure. FePt and related films show promise for development as heat-assisted magnetic recording media at extremely high areal densities. The self-assembled FePt arrays show potential for approaching the ultimate goal of single-grain-per-bit patterned media.
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Affiliation(s)
- Y F Xu
- Nebraska Center for Materials and Nanoscience, Department of Physics and Astronomy, University of Nebraska, Lincoln, NE 68588-0111, USA
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Abstract
Cr–N films were grown on Si (001) substrates by reactive magnetron sputtering under an N2/Ar atmosphere at room temperature. The composition of the films, expressed as Cr1−xNx, can be varied by changing the N2/Ar pressure ratio during the synthesis process. Crystalline states of Cr–N films have been studied using electron diffraction. It is well known that two intermediate phases, Cr2N (hexagonal) and CrN (cubic), exist in the Cr–N system, and small variations around the ideal stoichiometry are tolerated. The present study shows that cubic CrN with vacancies rather than hexagonal Cr2N may exist in a Cr–N film with a thickness of about 50 nm produced under a low N2partial pressure.
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Menon L, Bandyopadhyay S, Liu Y, Zeng H, Sellmyer DJ. Magnetic and structural properties of electrochemically self-assembled Fe1-xCox nanowires. J Nanosci Nanotechnol 2001; 1:149-152. [PMID: 12914045 DOI: 10.1166/jnn.2001.027] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Fe1-xCox (0 < or = x < or = 1) nanowires have been self-assembled by electrodeposition in porous alumina films. The crystal structure is bee at the Fe end. With increased addition of Co, the crystal structure remains bcc until about 67% addition of Co. At the Co end, the structure is a mixture of hcp and fcc. Magnetic studies show very high coercivities for the Fe-Co alloys in the bcc phase. For Fe0.67Co0.33 nanowires of diameter 9 nm, the coercivity is about 2900 Oe, whereas for Fe0.33Co0.67 nanowires, it is about 2850 Oe. Temperature and size dependence of magnetic properties show no indication of superparamagnetic effects down to wire diameters of 9 nm.
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Affiliation(s)
- L Menon
- Department of Electrical Engineering, Center for Materials Research and Analysis, University of Nebraska, Lincoln, Nebraska 68588-0511, USA
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Lorenz R, Hafner J, Jaswal SS, Sellmyer DJ. Disorder and noncollinear magnetism in permanent-magnet materials with the ThMn12 structure. Phys Rev Lett 1995; 74:3688-3691. [PMID: 10058268 DOI: 10.1103/physrevlett.74.3688] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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Woods JP, Patterson BM, Fernando AS, Jaswal SS, Welipitiya D, Sellmyer DJ. Electronic structures and Curie temperatures of iron-based rare-earth permanent-magnet compounds. Phys Rev B Condens Matter 1995; 51:1064-1072. [PMID: 9978258 DOI: 10.1103/physrevb.51.1064] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Al-Omari IA, Jaswal SS, Fernando AS, Sellmyer DJ, Hamdeh HH. Mössbauer, magnetic, and electronic-structure studies of YFe12-xMox compounds. Phys Rev B Condens Matter 1994; 50:12665-12671. [PMID: 9975430 DOI: 10.1103/physrevb.50.12665] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Kirby RD, Shen JX, Hardy RJ, Sellmyer DJ. Magnetization reversal in nanoscale magnetic films with perpendicular anisotropy. Phys Rev B Condens Matter 1994; 49:10810-10813. [PMID: 10009923 DOI: 10.1103/physrevb.49.10810] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Engelhardt MA, Jaswal SS, Sellmyer DJ. Photoemission and electronic structure of tungsten-based metallic glasses and alloys. Phys Rev B Condens Matter 1991; 44:12671-12679. [PMID: 9999440 DOI: 10.1103/physrevb.44.12671] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Jaswal SS, Yelon WB, Hadjipanayis GC, Wang YZ, Sellmyer DJ. Electronic and magnetic structures of the rare-earth compounds R2Fe17N xi. Phys Rev Lett 1991; 67:644-647. [PMID: 10044951 DOI: 10.1103/physrevlett.67.644] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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Shan ZS, Sellmyer DJ. Magnetism of rare-earth-transition-metal nanoscale multilayers. I. Experiments on Dy/Co, Dy/Fe, and Tb/Fe. Phys Rev B Condens Matter 1990; 42:10433-10445. [PMID: 9995305 DOI: 10.1103/physrevb.42.10433] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Shan ZS, Sellmyer DJ, Jaswal SS, Wang YJ, Shen JX. Magnetism of rare-earth-transition-metal nanoscale multilayers. II. Theoretical analysis of magnetization and perpendicular magnetic anisotropy. Phys Rev B Condens Matter 1990; 42:10446-10459. [PMID: 9995306 DOI: 10.1103/physrevb.42.10446] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Shan ZS, Sellmyer DJ, Jaswal SS, Wang YJ, Shen JX. Magnetism of rare-earth-transition-metal nanoscale multilayers. Phys Rev Lett 1989; 63:449-452. [PMID: 10041076 DOI: 10.1103/physrevlett.63.449] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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Aylesworth KD, Jaswal SS, Engelhardt MA, Zhao ZR, Sellmyer DJ. Electronic structure and properties of sputtered Ta-Cu films. Phys Rev B Condens Matter 1988; 37:2426-2432. [PMID: 9944788 DOI: 10.1103/physrevb.37.2426] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/11/2023]
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Jaswal SS, Sellmyer DJ, Engelhardt M, Zhao Z, Arko AJ, Xie K. Electronic structure, photoemission, and magnetism in Gd2Co and Er2Co glasses. Phys Rev B Condens Matter 1987; 35:996-1001. [PMID: 9941508 DOI: 10.1103/physrevb.35.996] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/11/2023]
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Misemer DK, Auluck S, Sellmyer DJ, Jaswal SS, Arko AJ. Photoemission, electronic structure, and magnetism in VPd3. Phys Rev B Condens Matter 1985; 31:3356-3360. [PMID: 9936221 DOI: 10.1103/physrevb.31.3356] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/11/2023]
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