Current-in-plane 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 spintronics applications. Recently, we have successfully grown Fe-doped FMSs; p-type (Ga,Fe)Sb with Curie temperature (TC) ≈ 340 K2 and n-type (In,Fe)Sb with TC ≈ 335 K3, which are promising for devices operating at room temperature. One of the important steps towards practical applications is to realize spin-valve effects in heterostructures containing Fe-doped FMSs. In this work, we demonstrate spin-valve magnetoresistance (MR) in all-semiconductor heterostructures containing Fe-doped FMS (Ga,Fe)Sb layers with TC ≈ 260 K. The samples examined here consist of (Ga0.75,Fe0.25)Sb (40 nm) / InAs (thickness tInAs = 0, 3, 6, 9 nm) / (Ga0.8,Fe0.2)Sb (40 nm) grown by low temperature molecular beam epitaxy (LT-MBE) [Fig. 1(a) and (b)]. In these structures, electrical current flows mainly in InAs due to the high resistivity of (Ga,Fe)Sb layers at low temperature (≤ 20 K)4. A clear spin-valve effect with an MR ratio of ~ 1.6% with an open minor loop is observed in the structure with tInAs = 3 nm at 3.7 K [Fig. 2], whose peaks (≈ ±0.1 T) correspond to the coercive forces in the magnetization characteristics of the (Ga,Fe)Sb layers obtained with superconducting quantum interference device (SQUID) magnetometry and anomalous Hall effect (AHE) measurements. We found that the spin-valve MR (MRSV) increases (from 0.03 to 1.6%) with decreasing tInAs (from 9 to 3 nm), which reflects the enhancement of spin-dependent scattering at the InAs/(Ga,Fe)Sb interfaces. This demonstration is the first important step towards device application of these promising high-TC FMSs.