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Lin MW, Chen PH, Yu LC, Shiu HW, Lai YL, Cheng SL, Wang JH, Wei DH, Lin HJ, Chin YY, Hsu YJ. Enhanced Magnetic Order and Reversed Magnetization Induced by Strong Antiferromagnetic Coupling at Hybrid Ferromagnetic-Organic Heterojunctions. ACS APPLIED MATERIALS & INTERFACES 2022; 14:16901-16910. [PMID: 35357129 DOI: 10.1021/acsami.2c01674] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Organic-molecular magnets based on a metal-organic framework with chemically tuned electronic and magnetic properties have been attracting tremendous attention due to their promising applications in molecular magnetic sensors, magnetic particle medicines, molecular spintronics, etc. Here, we investigated the magnetic behavior of a heterojunction comprising a ferromagnetic nickel (Ni) film and an organic semiconductor (OSC) 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ) layer. Through the magneto-optical Kerr effect (MOKE), a photoemission electron microscopy (PEEM), X-ray magnetic circular dichroism (XMCD), and X-ray photoelectron spectroscopy (XPS), we found that the adsorption of F4-TCNQ on Cu(100)/Ni not only reverses the in-plane magnetization direction originally exhibited by the Ni layer but also results in enhanced magnetic ordering. Furthermore, the cyano group (CN) in adsorbed F4-TCNQ was found spin-polarized along with conspicuous charge transfer with Ni. The density functional theory (DFT) calculations suggest that the experimentally found spin polarization originates from hybridization between the CN group's π orbitals and Ni's d band. These findings signify that the hybrid states at the organic-ferromagnet interface play a key role in tailoring the magnetic behavior of interfaces. For the case of the F4-TCNQ and Ni heterojunction reported here, interface coupling is an antiferromagnetic one.
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Affiliation(s)
- Ming-Wei Lin
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan, ROC
| | - Po-Hong Chen
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan, ROC
- Department of Engineering and System Science, National Tsing Hua University, Hsinchu 30013, Taiwan, ROC
| | - Li-Chung Yu
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan, ROC
| | - Hung-Wei Shiu
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan, ROC
| | - Yu-Ling Lai
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan, ROC
| | - Su-Ling Cheng
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan, ROC
| | - Jeng-Han Wang
- Department of Chemistry, National Taiwan Normal University, Taipei 10610, Taiwan, ROC
| | - Der-Hsin Wei
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan, ROC
- Department of Physics, National Chung Cheng University, Chiayi 621301, Taiwan, ROC
| | - Hong-Ji Lin
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan, ROC
| | - Yi-Ying Chin
- Department of Physics, National Chung Cheng University, Min-Hsiung, Chiayi, 62102, Taiwan, ROC
| | - Yao-Jane Hsu
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan, ROC
- Department of Photonics, National Cheng Kung University, Tainan 70101, Taiwan, ROC
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Farkaš B, de Leeuw NH. A Perspective on Modelling Metallic Magnetic Nanoparticles in Biomedicine: From Monometals to Nanoalloys and Ligand-Protected Particles. MATERIALS (BASEL, SWITZERLAND) 2021; 14:3611. [PMID: 34203371 PMCID: PMC8269646 DOI: 10.3390/ma14133611] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/25/2021] [Revised: 06/17/2021] [Accepted: 06/21/2021] [Indexed: 12/24/2022]
Abstract
The focus of this review is on the physical and magnetic properties that are related to the efficiency of monometallic magnetic nanoparticles used in biomedical applications, such as magnetic resonance imaging (MRI) or magnetic nanoparticle hyperthermia, and how to model these by theoretical methods, where the discussion is based on the example of cobalt nanoparticles. Different simulation systems (cluster, extended slab, and nanoparticle models) are critically appraised for their efficacy in the determination of reactivity, magnetic behaviour, and ligand-induced modifications of relevant properties. Simulations of the effects of nanoscale alloying with other metallic phases are also briefly reviewed.
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Affiliation(s)
- Barbara Farkaš
- School of Chemistry, Cardiff University, Cardiff CF10 3AT, UK;
| | - Nora H. de Leeuw
- School of Chemistry, Cardiff University, Cardiff CF10 3AT, UK;
- School of Chemistry, University of Leeds, Leeds LS2 9JT, UK
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Microscopic analysis of the composition driven spin-reorientation transition in Ni(x)Pd(1-x)/Cu(001). Ultramicroscopy 2015; 159 Pt 3:503-7. [PMID: 26092084 DOI: 10.1016/j.ultramic.2015.05.022] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2014] [Revised: 05/22/2015] [Accepted: 05/28/2015] [Indexed: 11/21/2022]
Abstract
The spin-reorientation transition (SRT) in epitaxial NixPd1-x/Cu(001) is studied by photoemission microscopy utilizing the X-ray magnetic circular dichroism effect at the Ni L2,3 edge. In a composition/thickness wedged geometry, a composition driven SRT could be observed between 37 ML and 60 ML, and 0 and 38% of Pd. Microspectroscopy in combination with azimuthal sample rotation confirms a magnetization preference changing from the [001] to an in-plane easy axis. At this increased thickness, the domain patterns arrange comparable to SRTs in ultrathin films. The images document domains equivalent to a canted state SRT, at which an additional effect of in-plane anisotropies could be identified.
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Balashov T, Buczek P, Sandratskii L, Ernst A, Wulfhekel W. Magnon dispersion in thin magnetic films. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2014; 26:394007. [PMID: 25212555 DOI: 10.1088/0953-8984/26/39/394007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Although the dispersion of magnons has been measured in many bulk materials, few studies deal with the changes in the dispersion when the material is in the form of a thin film, a system that is of interest for applications. Here we review inelastic tunneling spectroscopy studies of magnon dispersion in Mn/Cu3Au(1 0 0) and present new studies on Co and Ni thin films on Cu(1 0 0). The dispersion in Mn and Co films closely follows the dispersion of bulk samples with negligible dependence on thickness. The lifetime of magnons depends slightly on film thickness, and decreases considerably as the magnon energy increases. In Ni/Cu(1 0 0) films the thickness dependence of dispersion is much more pronounced. The measurements indicate a considerable mode softening for thinner films. Magnon lifetimes decrease dramatically near the edge of the Brillouin zone due to a close proximity of the Stoner continuum. The experimental study is supported by first-principles calculations.
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Affiliation(s)
- T Balashov
- Physikalisches Institut, Karlsruhe Institute of Technology, Wolfgang-Gaede Strasse 1, 76131 Karlsruhe, Germany
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Sakamaki M, Amemiya K. Enhancement of perpendicular magnetic anisotropy by compressive strain in alternately layered FeNi thin films. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2014; 26:166002. [PMID: 24695244 DOI: 10.1088/0953-8984/26/16/166002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The effect of the lattice strain on magnetic anisotropy of alternately layered FeNi ultrathin films grown on a substrate, Cu(tCu = 0-70 ML)/Ni(48)Cu(52)(124 ML)/Cu(0 0 1) single crystal, is systematically studied by means of in situ x-ray magnetic circular dichroism (XMCD) and reflection high-energy electron diffraction (RHEED) analyses. To investigate the magnetic anisotropy of the FeNi layer itself, a non-magnetic substrate is adopted. From the RHEED analysis, the in-plane lattice constant, ain, of the substrate is found to shrink by 0.8% and 0.5% at tCu = 0 and 10 ML as compared to that of bulk Cu, respectively. Fe L-edge XMCD analysis is performed for n ML FeNi films grown on various ain, and perpendicular magnetic anisotropy (PMA) is observed at n = 3 and 5, whereas the film with n = 7 shows in-plane magnetic anisotropy. Moreover, it is found that PMA is enhanced with decreasing ain, in the case where a Cu spacer layer is inserted. We suppose that magnetic anisotropy in the FeNi films is mainly carried by Fe, and the delocalization of the in-plane orbitals near the Fermi level increases the perpendicular orbital magnetic moment, which leads to the enhancement of PMA.
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Affiliation(s)
- M Sakamaki
- Institute of Materials Structure Science, High Energy Accelerator Research Organization, Tsukuba, Ibaraki 305-0801, Japan
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<i>In Situ</i> Observation of Magnetic Anisotropy Energy of Alternately Layered FeNi Thin Films. E-JOURNAL OF SURFACE SCIENCE AND NANOTECHNOLOGY 2012. [DOI: 10.1380/ejssnt.2012.97] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Lauhoff G, Vaz CAF, Bland JAC. Structure and magnetic properties of Ni/Cu/Fe/MgO(001) films. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2009; 21:156002. [PMID: 21825377 DOI: 10.1088/0953-8984/21/15/156002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The structural and magnetic properties of thin Ni films grown on Cu/Fe/MgO(001) and Cu/MgO(001) buffer layers are investigated and compared to those grown on Cu/Si(001). The use of an Fe seed layer a few monolayers thick leads to the epitaxial growth of high surface quality Cu(001) buffer layers on MgO(001), while Cu growth on the bare MgO(001) substrate results in polycrystalline films. Magneto-optic Kerr effect magnetometry shows that Ni films grown on Cu/Fe/MgO(001) exhibit dominant perpendicular magnetic anisotropy up to ∼90 Å, which is similar to that of Ni films grown on Cu/Si(001). The polycrystalline Ni films also exhibit perpendicular magnetic remanence, but with a dominant in-plane magnetization component.
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Dunn JH, Karis O, Andersson C, Arvanitis D, Carr R, Abrikosov IA, Sanyal B, Bergqvist L, Eriksson O. Vanishing magnetic interactions in ferromagnetic thin films. PHYSICAL REVIEW LETTERS 2005; 94:217202. [PMID: 16090342 DOI: 10.1103/physrevlett.94.217202] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/09/2004] [Indexed: 05/03/2023]
Abstract
We have used element-specific hysteresis measurements, based on the x-ray magnetic circular dichroism technique, to investigate magnetic trilayer structures composed of Fe and Ni layers. Within a critical regime we have discovered a class of structures in which the exchange interaction, the mechanism responsible for the macroscopic magnetism, can become vanishingly small. The experimental observations are supported by first principles theory and are explained as arising from a cancellation of several competing magnetic interactions. Hence, we have discovered a system with a novel exchange interaction between magnetic layers in direct contact that replaces the conventional exchange interaction in ferromagnets.
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