Microscopic Theory and Applications of Magnetoresistance Effects in Mesoscopic Ferromagnets and Altermagnets

DIPC Seminars

Speaker

Xian-Peng Zhang
Beijing Institute of Technology

When

2025/08/26
12:00

Place

DIPC Josebe Olarra Seminar Room

Host

Miguel Angel Cazalilla Gutierrez

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Spintronics aims to add new functionalities to the conventional electronics by using the interconversion of spin angular momentum between different carriers in solids. Especially, the spin exchange between conduction electron spins in a non-magnetic metal and magnetization in a ferromagnet is a central topic to manipulate magnetization for developing new types of magnetic memory devices. This report will focus on the microscopic theory and applications of magnetoresistance effects in mesoscopic ferromagnetic, altermagnetic, and magnetic heterostructures. First, I will introduce our microscopic theory established for spin Hall magnetoresistance in normal metal/ magnetic insulator heterostructures [1]. Second, we will present experimental validations of this microscopic theory under both paramagnetic [2] and ferromagnetic [3] conditions. It is well known that the magnetoresistance effect itself originates from the spin exchange coupling between localized magnetic moments and conduction electrons in magnetic materials, making it a highly challenging many-body open quantum problem. Based on this, in the third part, we apply the theory of open quantum systems to thoroughly investigate the quantum decoherence effects induced by spin exchange coupling. Within this framework, we develop a microscopic theory for the temperature- and magnetic-field-dependent anisotropic magnetoresistance and magnon magnetoresistance effects [4]. Furthermore, we explore the contribution of spin-splitting effects to magnetotransport properties in antiferromagnets and, based on this, propose an electrical readout scheme for antiferromagnetic memory devices [5].

References:
[1] Xian-Peng, Zhang, F. Sebastian, Bergeret and Vitaly N., Golovach*. “Theory of Spin Hall Magneto-resistance from a Microscopic Perspective.” Nano Lett., 2009,19(9), 6330.
[2] Koichi Oyanag, J. M. Gomez-Perez, X.-P. Zhang, ···, and Eiji Saitoh. “Paramagnetic spin Hall magneto-resistance.” arXiv:2008.02446.
[3] J. M. Gomez-Perez, Xian-Peng, Zhang, ···, and Felix Casanova*. “Strong interfacial exchange field in a heavy metal/ferromagnetic insulator system determined by spin
Hall magneto-resistance” Nano Lett., 20(9), 6815 (2020).
[4] X.-P. Zhang, X. Wang, Y. Yao*, “Microscopic theory of magnetoresistance in ferromagnetic materials.” arXiv:2406.13932 (2024).
[5] X.-P. Zhang, Xiaolong Fan, Xiangrong Wang* and Yugui Yao*, “Electrical readout of the Néel vector in an altermagnet” arXiv:2409.10088 (2024).