Theoretical Study on Anisotropic Magnetoresistance Effects of I//[100], I//[110], and I//[001] for Ferromagnets with A Crystal Field of Tetragonal Symmetry

Abstract

Using the electron scattering theory, we obtain analytic expressions for anisotropic magnetoresistance (AMR) ratios for ferromagnets with a crystal field of tetragonal symmetry. Here, a tetragonal distortion exists in the [001] direction, the magnetization ${\mbox{\boldmath $M$}}$ lies in the (001) plane, and the current ${\mbox{\boldmath $I$}}$ flows in the [100], [010], or [001] direction. When the ${\mbox{\boldmath $I$}}$ direction is denoted by $i$, we obtain the AMR ratio as ${\mathrm{AMR}}^i({\varphi }_i)=C_0^i+C_2^i\cos 2{\varphi }_i+C_4^i\cos 4{\varphi }_i\dots ={\sum }_{j=0,2,4,\dots }{C}_j^i\cos j{\varphi }_i$, with $i=[100]$, $[110]$, and $[001]$, ${\varphi }_{[100]}={\varphi }_{[001]}=\varphi$, and ${\varphi }_{[110]}={\varphi }^{\prime }$. The quantity $\varphi$ (${\varphi }^{\prime }$) is the relative angle between ${\mbox{\boldmath $M$}}$ and the $[100]$ ($[110]$) direction, and $C_j^i$ is a coefficient composed of a spin--orbit coupling constant, an exchange field, the crystal field, and resistivities. We elucidate the origin of $C_j^i\cos j{\varphi }_i$ and the features of $C_j^i$. In addition, we obtain the relation $C_4^{[100]}=-C_4^{[110]}$, which was experimentally observed for Ni, under a certain condition. We also qualitatively explain the experimental results of $C_2^{[100]}$, $C_4^{[100]}$, $C_2^{[110]}$, and $C_4^{[110]}$ at 293 K for Ni.

39 pages, 2 figures, free to download PDF from JPSJ site

References in corpus (2)

• Half-metallicity and anisotropy magnetoresistance properties of Heusler alloys Fe2Co1-xCrxSi
• Spin polarization ratios of resistivity and density of states estimated from anisotropic magnetoresistance ratio for nearly half-metallic ferromagnets

Cited by in corpus (2)

• Theoretical Study on Anisotropic Magnetoresistance Effects of Arbitrary Directions of Current and Magnetization for Ferromagnets: Application to Transverse Anisotropic Magnetoresistance Effect
• Enhancing atomic ordering, magnetic and transport properties of Mn2VGa Heusler alloy thin films toward negatively spin-polarized charge injection