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Mahendra A, Murmu PP, Acharya SK, Islam A, Fiedler H, Gupta P, Granville S, Kennedy J. Shaping Perpendicular Magnetic Anisotropy of Co 2MnGa Heusler Alloy Using Ion Irradiation for Magnetic Sensor Applications. Sensors (Basel) 2023; 23:s23094564. [PMID: 37177768 PMCID: PMC10181601 DOI: 10.3390/s23094564] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2023] [Revised: 03/27/2023] [Accepted: 05/05/2023] [Indexed: 05/15/2023]
Abstract
Magnetic sensors are key elements in many industrial, security, military, and biomedical applications. Heusler alloys are promising materials for magnetic sensor applications due to their high spin polarization and tunable magnetic properties. The dynamic field range of magnetic sensors is strongly related to the perpendicular magnetic anisotropy (PMA). By tuning the PMA, it is possible to modify the sensing direction, sensitivity and even the accuracy of the magnetic sensors. Here, we report the tuning of PMA in a Co2MnGa Heusler alloy film via argon (Ar) ion irradiation. MgO/Co2MnGa/Pd films with an initial PMA were irradiated with 30 keV 40Ar+ ions with fluences (ions·cm-2) between 1 × 1013 and 1 × 1015 Ar·cm-2, which corresponds to displacement per atom values between 0.17 and 17, estimated from Monte-Carlo-based simulations. The magneto optical and magnetization results showed that the effective anisotropy energy (Keff) decreased from ~153 kJ·m-3 for the un-irradiated film to ~14 kJ·m-3 for the 1 × 1014 Ar·cm-2 irradiated film. The reduced Keff and PMA are attributed to ion-irradiation-induced interface intermixing that decreased the interfacial anisotropy. These results demonstrate that ion irradiation is a promising technique for shaping the PMA of Co2MnGa Heusler alloy for magnetic sensor applications.
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Affiliation(s)
- Anmol Mahendra
- Robinson Research Institute, Victoria University of Wellington, Wellington 6140, New Zealand
- National Isotope Centre, GNS Science, Lower Hutt 5010, New Zealand
- The MacDiarmid Institute for Advanced Materials and Nanotechnology, Wellington 6140, New Zealand
| | - Peter P Murmu
- National Isotope Centre, GNS Science, Lower Hutt 5010, New Zealand
| | - Susant Kumar Acharya
- Robinson Research Institute, Victoria University of Wellington, Wellington 6140, New Zealand
- The MacDiarmid Institute for Advanced Materials and Nanotechnology, Wellington 6140, New Zealand
| | - Atif Islam
- Robinson Research Institute, Victoria University of Wellington, Wellington 6140, New Zealand
- The MacDiarmid Institute for Advanced Materials and Nanotechnology, Wellington 6140, New Zealand
| | - Holger Fiedler
- National Isotope Centre, GNS Science, Lower Hutt 5010, New Zealand
| | - Prasanth Gupta
- National Isotope Centre, GNS Science, Lower Hutt 5010, New Zealand
- The MacDiarmid Institute for Advanced Materials and Nanotechnology, Wellington 6140, New Zealand
| | - Simon Granville
- Robinson Research Institute, Victoria University of Wellington, Wellington 6140, New Zealand
- The MacDiarmid Institute for Advanced Materials and Nanotechnology, Wellington 6140, New Zealand
| | - John Kennedy
- National Isotope Centre, GNS Science, Lower Hutt 5010, New Zealand
- The MacDiarmid Institute for Advanced Materials and Nanotechnology, Wellington 6140, New Zealand
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Kennedy JV, Trompetter WJ, Murmu PP, Leveneur J, Gupta P, Fiedler H, Fang F, Futter J, Purcell C. Evolution of Rutherford’s ion beam science to applied research activities at GNS Science. J R Soc N Z 2021. [DOI: 10.1080/03036758.2021.1897021] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Affiliation(s)
- John V. Kennedy
- Materials Team, National Isotope Centre, GNS Science, Lower Hutt, New Zealand
| | | | - Peter P. Murmu
- Materials Team, National Isotope Centre, GNS Science, Lower Hutt, New Zealand
| | - Jerome Leveneur
- Materials Team, National Isotope Centre, GNS Science, Lower Hutt, New Zealand
| | - Prasanth Gupta
- Materials Team, National Isotope Centre, GNS Science, Lower Hutt, New Zealand
| | - Holger Fiedler
- Materials Team, National Isotope Centre, GNS Science, Lower Hutt, New Zealand
| | - Fang Fang
- Materials Team, National Isotope Centre, GNS Science, Lower Hutt, New Zealand
| | - John Futter
- Materials Team, National Isotope Centre, GNS Science, Lower Hutt, New Zealand
| | - Chris Purcell
- Materials Team, National Isotope Centre, GNS Science, Lower Hutt, New Zealand
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Ahmed S, Ding X, Murmu PP, Bao N, Liu R, Kennedy J, Wang L, Ding J, Wu T, Vinu A, Yi J. High Coercivity and Magnetization in WSe 2 by Codoping Co and Nb. Small 2020; 16:e1903173. [PMID: 31441228 DOI: 10.1002/smll.201903173] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Revised: 07/22/2019] [Indexed: 06/10/2023]
Abstract
Introducing ferromagnetism in transition metal dichalcogenides has attracted lots of attention due to the possible applications in spintronics devices. Generally, single magnetic element doping is used to introduce magnetism. However, mostly, weak ferromagnetism is observed. In this work, codoping of two kinds of transition metals (Nb and Co) into WSe2 is used to study its magnetic properties. In detail, single crystal WSe2 is codoped with 4 at% Co and various concentrations of Nb by employing the physical ion implantation method. Raman, X-ray diffraction and X-ray photoelectron spectroscopy results reveal the effective substitutional doping of implanted elements (Co and Nb). Magnetic measurements illustrate that both un-doped and 4 at% Co doped WSe2 show weak ferromagnetism whereas magnetization is strongly enhanced when Co and Nb are codoped into WSe2 . The magnetization is comparable with a ferromagnet, which may be attributed to Co, Nb doping and defects. In addition, a large coercivity of ≈1.2 kOe is observed in the 1 at% Nb-4 at% Co codoped WSe2 sample, which may be ascribed to the combined effect of doping-induced stress, defect-dictated pinning and anisotropy of NbSe bond owing to the charge transfer between Nb and Se ions.
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Affiliation(s)
- Sohail Ahmed
- School of Materials Science and Engineering, UNSW, Sydney, NSW, 2052, Australia
| | - Xiang Ding
- School of Materials Science and Engineering, UNSW, Sydney, NSW, 2052, Australia
| | - Peter P Murmu
- National Isotope Centre, GNS Science, P.O. Box 31312, Lower Hutt, 5010, New Zealand
| | - Nina Bao
- Department of Materials Science and Engineering, National University of Singapore, Singapore, 119260, Singapore
| | - Rong Liu
- SIMS Facility, Office of the Deputy-Vice-Chancellor (R&D), Western Sydney University, Penrith, NSW, 2751, Australia
| | - John Kennedy
- National Isotope Centre, GNS Science, P.O. Box 31312, Lower Hutt, 5010, New Zealand
| | - Lan Wang
- School of Science, RMIT University, Melbourne, Victoria, 3001, Australia
| | - Jun Ding
- Department of Materials Science and Engineering, National University of Singapore, Singapore, 119260, Singapore
| | - Tom Wu
- School of Materials Science and Engineering, UNSW, Sydney, NSW, 2052, Australia
| | - Ajayan Vinu
- Global Innovative Centre for Advanced Nanomaterials, School of Engineering, The University of Newcastle, Callaghan, NSW, 2308, Australia
| | - Jiabao Yi
- Global Innovative Centre for Advanced Nanomaterials, School of Engineering, The University of Newcastle, Callaghan, NSW, 2308, Australia
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Sandupatla A, Arulkumaran S, Ranjan K, Ng GI, Murmu PP, Kennedy J, Nitta S, Honda Y, Deki M, Amano H. Low Voltage High-Energy α-Particle Detectors by GaN-on-GaN Schottky Diodes with Record-High Charge Collection Efficiency. Sensors (Basel) 2019; 19:s19235107. [PMID: 31766532 PMCID: PMC6928794 DOI: 10.3390/s19235107] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/10/2019] [Revised: 11/14/2019] [Accepted: 11/19/2019] [Indexed: 11/22/2022]
Abstract
A low voltage (−20 V) operating high-energy (5.48 MeV) α-particle detector with a high charge collection efficiency (CCE) of approximately 65% was observed from the compensated (7.7 × 1014 /cm3) metalorganic vapor phase epitaxy (MOVPE) grown 15 µm thick drift layer gallium nitride (GaN) Schottky diodes on free-standing n+-GaN substrate. The observed CCE was 30% higher than the bulk GaN (400 µm)-based Schottky barrier diodes (SBD) at −20 V. This is the first report of α–particle detection at 5.48 MeV with a high CCE at −20 V operation. In addition, the detectors also exhibited a three-times smaller variation in CCE (0.12 %/V) with a change in bias conditions from −120 V to −20 V. The dramatic reduction in CCE variation with voltage and improved CCE was a result of the reduced charge carrier density (CCD) due to the compensation by Mg in the grown drift layer (DL), which resulted in the increased depletion width (DW) of the fabricated GaN SBDs. The SBDs also reached a CCE of approximately 96.7% at −300 V.
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Affiliation(s)
- Abhinay Sandupatla
- School of Electrical and Electronics Engineering, Nanyang Technological University, Singapore 639798, Singapore
- Correspondence: (A.S.); (G.I.N.)
| | - Subramaniam Arulkumaran
- Temasek Laboratories @ NTU, Research Techno Plaza, 50 Nanyang Drive, Singapore 639798, Singapore (K.R.)
- Center for Integrated Research of Future Electronics (CIRFE), IMaSS, Nagoya University, Nagoya 464-8603, Japan (Y.H.); (M.D.); (H.A.)
| | - Kumud Ranjan
- Temasek Laboratories @ NTU, Research Techno Plaza, 50 Nanyang Drive, Singapore 639798, Singapore (K.R.)
| | - Geok Ing Ng
- School of Electrical and Electronics Engineering, Nanyang Technological University, Singapore 639798, Singapore
- Temasek Laboratories @ NTU, Research Techno Plaza, 50 Nanyang Drive, Singapore 639798, Singapore (K.R.)
- Correspondence: (A.S.); (G.I.N.)
| | - Peter P. Murmu
- National Isotope Center, GNS Science, Lower Hutt 5010, New Zealand; (P.P.M.); (J.K.)
| | - John Kennedy
- National Isotope Center, GNS Science, Lower Hutt 5010, New Zealand; (P.P.M.); (J.K.)
| | - Shugo Nitta
- Center for Integrated Research of Future Electronics (CIRFE), IMaSS, Nagoya University, Nagoya 464-8603, Japan (Y.H.); (M.D.); (H.A.)
| | - Yoshio Honda
- Center for Integrated Research of Future Electronics (CIRFE), IMaSS, Nagoya University, Nagoya 464-8603, Japan (Y.H.); (M.D.); (H.A.)
| | - Manato Deki
- Center for Integrated Research of Future Electronics (CIRFE), IMaSS, Nagoya University, Nagoya 464-8603, Japan (Y.H.); (M.D.); (H.A.)
| | - Hiroshi Amano
- Center for Integrated Research of Future Electronics (CIRFE), IMaSS, Nagoya University, Nagoya 464-8603, Japan (Y.H.); (M.D.); (H.A.)
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Kennedy J, Murmu PP, Leveneur J, Williams VM, Moody RL, Maity T, Chong SV. Enhanced Power Factor and Increased Conductivity of Aluminum Doped Zinc Oxide Thin Films for Thermoelectric Applications. J Nanosci Nanotechnol 2018; 18:1384-1387. [PMID: 29448596 DOI: 10.1166/jnn.2018.14105] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [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
We report the structural, electrical and thermopower properties of un-doped and Al doped zinc oxide (ZnO) thin films. Al doping was carried out using 25 keV Al+ implantation with 0.1, 1 and 2% Al into ZnO. X-ray diffraction measurements showed that the lattice parameters were larger than the bulk values, which is consistent with the incorporation of Al atoms at interstitials. Al doping increased the electrical conductivity from 100 (Ωcm)-1 in the un-doped ZnO film to 598 (Ωcm)-1 in the 2% Al doped ZnO film. Electron doping by Al resulted in an increase in the carrier concentration and it had an advantageous effect on the mobility where it was highest for 2% doping. The absolute value of the Seebeck coefficient systematically increased for un-doped, 1% and 2% Al doped ZnO films where the room temperature values were -50.8, -60.9 and -66.3 μV/K, respectively. The power factor increased significantly from 2.58 × 10-5 W/mK2 in un-doped ZnO film to 2.63 × 10-4 W/mK2 in 2% Al doped ZnO film. Our results suggest that the ion beam method is a suitable technique to enhance the thermoelectric properties of ZnO.
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Affiliation(s)
- John Kennedy
- National Isotope Centre, GNS Science, P.O. Box 31312, Lower Hutt 5010, New Zealand
| | - Peter P Murmu
- National Isotope Centre, GNS Science, P.O. Box 31312, Lower Hutt 5010, New Zealand
| | - Jérôme Leveneur
- National Isotope Centre, GNS Science, P.O. Box 31312, Lower Hutt 5010, New Zealand
| | - V M Williams
- The MacDiarmid Institute for Advanced Materials and Nanotechnology, 6140, New Zealand
| | - Ryan L Moody
- National Isotope Centre, GNS Science, P.O. Box 31312, Lower Hutt 5010, New Zealand
| | - Tanmay Maity
- The MacDiarmid Institute for Advanced Materials and Nanotechnology, 6140, New Zealand
| | - Shen V Chong
- The MacDiarmid Institute for Advanced Materials and Nanotechnology, 6140, New Zealand
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Murmu PP, Kennedy J, Williams GVM, Prakash T, Leveneur J, Chong SV, Rubanov S. Synthesis and Compositional Analysis of Permalloy Powder Prepared by Arc-Discharge. J Nanosci Nanotechnol 2015; 15:9612-9616. [PMID: 26682386 DOI: 10.1166/jnn.2015.10731] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We report the synthesis, compositional, structural and magnetic properties of permalloy powders prepared using an arc-discharge method under different atmospheres. Ion beam analysis results showed that powder prepared in air had a higher concentration of oxygen than those prepared under nitrogen or argon atmospheres. X-ray diffraction measurements showed that powders prepared in air contained magnetite (Fe3O4) and other phases, while powders prepared under nitrogen or argon predominately contained permalloy. The permalloy powders contained a broad range of particle sizes, and nanoparticles as small as 10 nm were evident from transmission electron microscopy data. The saturation magnetizations were significantly lower for the powders prepared in air than those prepared under nitrogen or argon. This can be attributed to oxidation, where the saturation magnetization is predominately from Fe3O4 for powders made in air. The coercive fields were also significantly larger for powders prepared in air, which is consistent with the powders containing different phases when compared with the permalloy powders. Our results show that permalloy powders can be made in nitrogen and argon, allowing for the production of low oxygen content permalloy powders for device applications. Our results also suggest that the use of an iron anode could result in Fe3O4 powders.
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Murmu PP, Markwitz A, Suschke K, Futter J. A novel radial anode layer ion source for inner wall pipe coating and materials modification--hydrogenated diamond-like carbon coatings from butane gas. Rev Sci Instrum 2014; 85:085118. [PMID: 25173323 DOI: 10.1063/1.4892813] [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: 06/03/2023]
Abstract
We report a new ion source development for inner wall pipe coating and materials modification. The ion source deposits coatings simultaneously in a 360° radial geometry and can be used to coat inner walls of pipelines by simply moving the ion source in the pipe. Rotating parts are not required, making the source ideal for rough environments and minimizing maintenance and replacements of parts. First results are reported for diamond-like carbon (DLC) coatings on Si and stainless steel substrates deposited using a novel 360° ion source design. The ion source operates with permanent magnets and uses a single power supply for the anode voltage and ion acceleration up to 10 kV. Butane (C4H10) gas is used to coat the inner wall of pipes with smooth and homogeneous DLC coatings with thicknesses up to 5 μm in a short time using a deposition rate of 70 ± 10 nm min(-1). Rutherford backscattering spectrometry results showed that DLC coatings contain hydrogen up to 30 ± 3% indicating deposition of hydrogenated DLC (a-C:H) coatings. Coatings with good adhesion are achieved when using a multiple energy implantation regime. Raman spectroscopy results suggest slightly larger disordered DLC layers when using low ion energy, indicating higher sp(3) bonds in DLC coatings. The results show that commercially interesting coatings can be achieved in short time.
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Affiliation(s)
- Peter P Murmu
- National Isotope Centre, GNS Science, P.O. Box 31312, Lower Hutt 5010, New Zealand
| | - Andreas Markwitz
- National Isotope Centre, GNS Science, P.O. Box 31312, Lower Hutt 5010, New Zealand
| | - Konrad Suschke
- National Isotope Centre, GNS Science, P.O. Box 31312, Lower Hutt 5010, New Zealand
| | - John Futter
- National Isotope Centre, GNS Science, P.O. Box 31312, Lower Hutt 5010, New Zealand
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