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Thickness-induced reversal of magnetoresistance polarity in CoFeNi-based MTJs: evolution from coherent switching to vortex-state transport.

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Title: Thickness-induced reversal of magnetoresistance polarity in CoFeNi-based MTJs: evolution from coherent switching to vortex-state transport.
Authors: Gayathri, S. Vimala1 (AUTHOR), Subbulekshmi, D.1 (AUTHOR) subbulekshmi.d@vit.ac.in, Kennedy, L. John2 (AUTHOR)
Source: Journal of Materials Science. Apr2026, Vol. 61 Issue 13, p8644-8663. 20p.
Subjects: Tunnel magnetoresistance, Magnetization reversal, Spintronics, Magnetoresistance, Cobalt nickel alloys, Magnetization, Magnetic tunnelling
Abstract: Magnetic Tunnel Junctions (MTJs) operate on the principle of spin-dependent tunneling through an ultrathin insulating barrier, and their magnetoresistive response depends on the relative alignment of magnetization within the two ferromagnetic layers. In this work, the free-layer thickness controls the magnetization states and magnetotransport behavior of CoFeNi/MgO/CoFeNi MTJs by means of micromagnetic simulations. The findings show a clear transition in thickness from coherent single-domain rotation towards vortex-mediated reversal. This transition, in turn, directly controls the Tunneling Magnetoresistance (TMR) observed to change in polarity from +199% at 25 nm to −344% at 100 nm. The coercive field moderately increases from 22.3 mT to 24.9 mT as a function of thickness, which attests to the transition between uniform and non-collinear magnetization configurations. Thus, the polarity inversion in sign arises from the formation of vortex states at larger thicknesses, which create non-collinear interfacial spin alignments and enhanced spin-flip tunneling, resulting in the reversal of the effective spin polarization. The research provides systematic insights into the thickness-dependent magnetic configurations, energy landscapes, and transport behavior in CoFeNi-based MTJs, with conclusions important for further prospective memory and logic devices. [ABSTRACT FROM AUTHOR]
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Database: Engineering Source
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Abstract:Magnetic Tunnel Junctions (MTJs) operate on the principle of spin-dependent tunneling through an ultrathin insulating barrier, and their magnetoresistive response depends on the relative alignment of magnetization within the two ferromagnetic layers. In this work, the free-layer thickness controls the magnetization states and magnetotransport behavior of CoFeNi/MgO/CoFeNi MTJs by means of micromagnetic simulations. The findings show a clear transition in thickness from coherent single-domain rotation towards vortex-mediated reversal. This transition, in turn, directly controls the Tunneling Magnetoresistance (TMR) observed to change in polarity from +199% at 25 nm to −344% at 100 nm. The coercive field moderately increases from 22.3 mT to 24.9 mT as a function of thickness, which attests to the transition between uniform and non-collinear magnetization configurations. Thus, the polarity inversion in sign arises from the formation of vortex states at larger thicknesses, which create non-collinear interfacial spin alignments and enhanced spin-flip tunneling, resulting in the reversal of the effective spin polarization. The research provides systematic insights into the thickness-dependent magnetic configurations, energy landscapes, and transport behavior in CoFeNi-based MTJs, with conclusions important for further prospective memory and logic devices. [ABSTRACT FROM AUTHOR]
ISSN:00222461
DOI:10.1007/s10853-026-12339-1