Magnetoresistance
has been one of the important phenomena in spintronics for a long time.
Recently, a novel type of magnetoresistance called spin Hall magnetoresistance
(SMR) has been observed in a bilayer system composed of a normal metal and a
ferromagnetic insulator. While its qualitative behavior has been explained well
by the semiclassical theory based on a mixing conductance [1], this theory
could not describe temperature dependence of the SMR. In this talk, I present a
microscopic theory [2,3] for SMR by formulating a spin conductance in terms of
spin susceptibilities. We reveal that SMR is composed of static and dynamic
parts; The static part originates from spin flip caused
by an interfacial exchange coupling. On the other hand, the dynamic
part, which is induced by the creation or annihilation of magnons, has an
opposite sign from the static part. I also present the temperature dependence
of SMR derived by our theory using the spin-wave approximation [2] and a
quantum Monte Carlo simulation [3]. [1] Y. T. Chen, et al., Phys. Rev. B 87, 144411 (2013).
[2] T. Kato, Y. Ohnuma, and M. Matsuo, Phys. Rev. B 102, 094437 (2020).
[3] T. Ishikawa, M. Matsuo, and T. Kato, Phys. Rev. B 107, 054426 (2023).
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Contact : Takeo KATO（ext. 63255）
