The magnetic anisotropy properties of Ga0.93Mn0.07As by low-temperature annealing

Abstract

The magnetic anisotropy properties of (Ga, Mn)As epilayers are dependent on strain, thickness, substrates orientation, measurement temperature and shape. Systematic study magnetic anisotropy is important owing to they will strongly influence its application of spintronic devices. The effect of low-temperature annealing on the lattice constant and magnetic properties of ternary (Ga, Mn)As grown on GaAs substrates has been intensely studied. Here, we report magnetic anisotropy properties of Ga0.93Mn0.07As by low-temperature annealing.The Ga0.93Mn0.07As sample was grown on (001) semi-insulating GaAs substrates by a Varian Modular GEN-II MBE system. The surface reconstruction of the samples during growth was monitored in situ with the reflection high-energy electron diffraction (RHEED). After growth, sample was cleaved into pieces for various characterizations. The Mn concentrations were determined by a calibration curve based on the electron microprobe analysis (EMPA). The crystalline structures were examined by double-crystal x-ray diffraction (DXRD). Magnetic properties were measured by a Quantum Design MPMS2 superconducting quantum interference device (SQUID) magnetometer. To measure the magnetic properties of Ga0.93Mn0.07As epilayers the samples are cooled down to 10 K under an external field of 1000 Oe applied along the measurement axis. Then, field is removed, and projection of the remnant magnetization along the measurement axis is recorded as a function of increasing temperature. The temperature dependence of magnetization (M-T) curves of as-grown and annealed samples, were measured in small magnetic field (H = 1 Oe) applied in-plane directions. The M-T curves show in Fig. 1. Post-annealing with 250 oC for 1.5 hrs, the Curie temperatures (TC) value increases from 80 Kto 160 K.The magnetic field dependence of magnetization (M-H) curves was measured with applied fields along [110], [-110], [100] and [010] axis, respectively. M-H curves of as-grown and annealed samples are shown. The easy axis can be rotated from [100] direction to [010] direction by low-temperature annealing. And the coercivity field is from 50 G decrease to 18 G. Detailed studies of the effect of low-temperature annealing on magnetic anisotropy properties were discussed.