Large and Local Magnetoresistance in a State-of-the-Art Perpendicular Magnetic Medium

Morgan Williamson,1,2 Cheng Wang,3 Pin-Wei Huang,3 Ganping Ju,3 Maxim Tsoi1,2 1Physics Department, University of Texas at Austin, Austin, TX 78712, USA; 2Texas Materials Institute, University of Texas at Austin, Austin, TX 78712, USA; 3Fremont Research Center, Seagate Technology, Fremont, CA 94538,...

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Autores principales:	Williamson M, Wang C, Huang PW, Ju G, Tsoi M
Formato:	article
Lenguaje:	EN
Publicado:	Dove Medical Press 2021
Materias:	magnetoresistance granular magnetic medium tunnel magnetoresistance hard disc drives. Medical technology R855-855.5 Chemical technology TP1-1185
Acceso en línea:	https://doaj.org/article/37b9b44714dd40a7bec92288832708c7
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spelling	oai:doaj.org-article:37b9b44714dd40a7bec92288832708c72021-12-02T14:01:50ZLarge and Local Magnetoresistance in a State-of-the-Art Perpendicular Magnetic Medium1177-8903https://doaj.org/article/37b9b44714dd40a7bec92288832708c72021-01-01T00:00:00Zhttps://www.dovepress.com/large-and-local-magnetoresistance-in-a-state-of-the-art-perpendicular--peer-reviewed-article-NSAhttps://doaj.org/toc/1177-8903Morgan Williamson,1,2 Cheng Wang,3 Pin-Wei Huang,3 Ganping Ju,3 Maxim Tsoi1,2 1Physics Department, University of Texas at Austin, Austin, TX 78712, USA; 2Texas Materials Institute, University of Texas at Austin, Austin, TX 78712, USA; 3Fremont Research Center, Seagate Technology, Fremont, CA 94538, USACorrespondence: Maxim Tsoi Email tsoi@physics.utexas.eduPurpose: Magnetotransport properties of granular oxide-segregated CoPtCr films were studied on both macroscopic and microscopic length scales by performing bulk and point-contact magnetoresistance measurements, respectively. Such a perpendicular magnetic medium is used in state-of-the-art hard disc drives and, when combined with magnetotransport phenomena for read/write operations, may lead to a novel concept for magnetic recording with high areal density.Materials and Methods: The CoPtCr films were deposited by an epitaxy-like sputtering and contained several perpendicularly magnetized granular-media layers with different coercivities; they are very much like the state-of-the-art perpendicular magnetic medium, which can be found in today’s hard disc drives. Magnetoresistive properties of bulk films were assessed by measuring the film resistance in the standard Van der Pauw geometry, while the local transport was probed by the point-contact technique.Results: The bulk measurements showed only a negligible magnetoresistance of less than 0.02%. In contrast, the local point-contact measurements revealed giant-magnetoresistance-like changes ΔR in local resistance of the contact R with more than 10,000% ratio ΔR/R.Conclusion: The observed large and local magnetoresistive effect could be tentatively attributed to a tunnel magnetoresistance between oxide-segregated CoPtCr grains with different coercivities. The tunneling picture of electronic transport in our granular medium was confirmed by the observation of tunneling-like current–voltage characteristics of the contacts and bias dependence of the contact magnetoresistance – both the local point-contact resistance and magnetoresistance were found to decrease with the applied dc bias.Keywords: magnetoresistance, granular magnetic medium, tunnel magnetoresistance, hard disc drivesWilliamson MWang CHuang PWJu GTsoi MDove Medical Pressarticlemagnetoresistancegranular magnetic mediumtunnel magnetoresistancehard disc drives.Medical technologyR855-855.5Chemical technologyTP1-1185ENNanotechnology, Science and Applications, Vol Volume 14, Pp 1-6 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	magnetoresistance granular magnetic medium tunnel magnetoresistance hard disc drives. Medical technology R855-855.5 Chemical technology TP1-1185
spellingShingle	magnetoresistance granular magnetic medium tunnel magnetoresistance hard disc drives. Medical technology R855-855.5 Chemical technology TP1-1185 Williamson M Wang C Huang PW Ju G Tsoi M Large and Local Magnetoresistance in a State-of-the-Art Perpendicular Magnetic Medium
description	Morgan Williamson,1,2 Cheng Wang,3 Pin-Wei Huang,3 Ganping Ju,3 Maxim Tsoi1,2 1Physics Department, University of Texas at Austin, Austin, TX 78712, USA; 2Texas Materials Institute, University of Texas at Austin, Austin, TX 78712, USA; 3Fremont Research Center, Seagate Technology, Fremont, CA 94538, USACorrespondence: Maxim Tsoi Email tsoi@physics.utexas.eduPurpose: Magnetotransport properties of granular oxide-segregated CoPtCr films were studied on both macroscopic and microscopic length scales by performing bulk and point-contact magnetoresistance measurements, respectively. Such a perpendicular magnetic medium is used in state-of-the-art hard disc drives and, when combined with magnetotransport phenomena for read/write operations, may lead to a novel concept for magnetic recording with high areal density.Materials and Methods: The CoPtCr films were deposited by an epitaxy-like sputtering and contained several perpendicularly magnetized granular-media layers with different coercivities; they are very much like the state-of-the-art perpendicular magnetic medium, which can be found in today’s hard disc drives. Magnetoresistive properties of bulk films were assessed by measuring the film resistance in the standard Van der Pauw geometry, while the local transport was probed by the point-contact technique.Results: The bulk measurements showed only a negligible magnetoresistance of less than 0.02%. In contrast, the local point-contact measurements revealed giant-magnetoresistance-like changes ΔR in local resistance of the contact R with more than 10,000% ratio ΔR/R.Conclusion: The observed large and local magnetoresistive effect could be tentatively attributed to a tunnel magnetoresistance between oxide-segregated CoPtCr grains with different coercivities. The tunneling picture of electronic transport in our granular medium was confirmed by the observation of tunneling-like current–voltage characteristics of the contacts and bias dependence of the contact magnetoresistance – both the local point-contact resistance and magnetoresistance were found to decrease with the applied dc bias.Keywords: magnetoresistance, granular magnetic medium, tunnel magnetoresistance, hard disc drives
format	article
author	Williamson M Wang C Huang PW Ju G Tsoi M
author_facet	Williamson M Wang C Huang PW Ju G Tsoi M
author_sort	Williamson M
title	Large and Local Magnetoresistance in a State-of-the-Art Perpendicular Magnetic Medium
title_short	Large and Local Magnetoresistance in a State-of-the-Art Perpendicular Magnetic Medium
title_full	Large and Local Magnetoresistance in a State-of-the-Art Perpendicular Magnetic Medium
title_fullStr	Large and Local Magnetoresistance in a State-of-the-Art Perpendicular Magnetic Medium
title_full_unstemmed	Large and Local Magnetoresistance in a State-of-the-Art Perpendicular Magnetic Medium
title_sort	large and local magnetoresistance in a state-of-the-art perpendicular magnetic medium
publisher	Dove Medical Press
publishDate	2021
url	https://doaj.org/article/37b9b44714dd40a7bec92288832708c7
work_keys_str_mv	AT williamsonm largeandlocalmagnetoresistanceinastateoftheartperpendicularmagneticmedium AT wangc largeandlocalmagnetoresistanceinastateoftheartperpendicularmagneticmedium AT huangpw largeandlocalmagnetoresistanceinastateoftheartperpendicularmagneticmedium AT jug largeandlocalmagnetoresistanceinastateoftheartperpendicularmagneticmedium AT tsoim largeandlocalmagnetoresistanceinastateoftheartperpendicularmagneticmedium
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Large and Local Magnetoresistance in a State-of-the-Art Perpendicular Magnetic Medium

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