Spin-valve magnetoresistance in ferromagnetic semiconductor (Ga, Fe)Sb heterostructures with high Curie temperature

Abstract

Ferromagnetic semiconductors (FMSs), which show both ferromagnetic and semiconducting characteristics, are promising materials for future low-power spintronics devices. Among various FMSs, Fe-doped III-V FMSs are promising, because both p-type and n-type materials are available and the highest Curie temperature ( $T_{\mathrm{C}}$ ) exceeds room temperature. In this work, we demonstrate clear magnetoresistance due to the spin valve effect in ferromagnetic heterostructures containing high- $T_{\mathrm{C}}$ (Ga, Fe)Sb. The samples examined here consist of (Ga 0.75 , Fe 0.25 )Sb ( $40 \text{nm}, T_{\mathrm{C}} > 320 \mathrm{K}$ ) / InAs (thickness $t=0, 3, 6, \text{nm}$ ) / (Ga 0.8 , Fe 0.2 )Sb ( $40 \text{nm}, T_{\mathrm{C}} > 320 \mathrm{K}$ ) grown by low-temperature molecular-beam epitaxy. Clear MR of ∼2% with an open minor loop is observed at 3.7 K when $t =3 \text{nm}$ , whose peaks (⋍ ±0.1 T) are consistent with the coercive forces of the (Ga, Fe)Sb layers obtained with superconducting quantum interference device (SQUID) magnetometry. We found that the GMR ratio increases (from 0.03 to 1.28%) with decreasing $t$ (from 9 to 3 nm), which is caused by the enhancement of spin-dependent scattering at the InAs/(Ga, Fe)Sb interfaces. This is the first demonstration of the spin-valve effect in Fe-doped FMS heterostructures, paving the way for device applications of high- $T_{\mathrm{C}}$ FMSs.