报告题目： Intuitive Explanation of Anisotropic Magnetoresistance (AMR) Effect and Necessary Condition for Half-Metallic Ferromagnet “Negative AMR’’

报告人： Satoshi Kokado Shizuoka University, Japan

报告时间：2017-1-6 10:00

报告地点： 理科楼三楼报告厅（C302）

摘要：The anisotropic magnetoresistance (AMR) effect is a fundamental phenomenon in which a resistivity depends on the relative angle between the current I and magnetization M directions [1-9]. The efficiency of the effect “AMR ratio” is defined by , where () is a resistivity for I//M (IM). The AMR ratio has been experimentally investigated for various ferromagnets (FMs) for the last 160 years. In particular, it has been reported that Fe [1], Co, and Ni exhibit positive AMR ratios, while Fe4N [1,2,5] and half-metallic FMs show negative AMR ratios. Systematic analyses for such AMR ratios, however, have been scarce so far. In addition, an intuitive explanation about the AMR effects has seldom been given.

In our study, we derived a general expression of the AMR ratio using the two-current model with all s-d scattering processes [6-9]. The d states were obtained from a Hamiltonian with the spin-orbit interaction VSO.Using the expression, we found a relation between the sign of the AMR ratio and the s-d scattering process [6,7]. In addition, the AMR effects could be intuitively explained by using the dstates,which are distorted by VSO [7].We also showed that the negative AMR ratio is a necessary condition for the half-metallic FMs [3,4,6,7,9].

References

[1] M. Tsunoda, Y. Komasaki, S. Kokado et al., Appl. Phys. Express 2, 083001 (2009).

[2] M. Tsunoda, H. Takahashi, S. Kokado et al., Appl. Phys. Express 3, 113003 (2010).
[3] F. Yang, Y. Sakuraba, S. Kokado et al., Phys. Rev. B 86, 020409 (2012).

[4] Y. Sakuraba, S. Kokado et al., Appl. Phys. Lett. 104, 172407 (2014).

[5] K. Kabara, M. Tsunoda, and S. Kokado, Appl. Phys. Express 7, 063003 (2014).

[6] S. Kokado, M. Tsunoda et al., J. Phys. Soc. Jpn. 81, 024705 (2012).

[7] S. Kokado and M. Tsunoda, Adv. Mater. Res. 750-752, 978 (2013).

[8] S. Kokado and M. Tsunoda, J. Phys. Soc. Jpn. 84, 094710 (2015).

[9] S. Kokado, Y. Sakuraba, and M. Tsunoda, Jpn. J. Appl. Phys. 55, 108004 (2016).