Magnetic anisotropy of III-Mn-V dilute ferromagnetic semiconductors

As one of the most important physical properties of III-Mn-V dilute ferromagnetic semiconductors (DFS), the magnetic anisotropy could be tailored by Mn/hole concentrations and by the lattice strain [1, 2]. Particularly, the crystal symmetry lowering in-plane uniaxial anisotropy still remains one of the most puzzling properties of the DFS family. Using a perturbation method and ab initio computations, Birowska et al. showed that the preferential distribution of Mn along (Ga,Mn)As [11(_)0] can produce bulk uniaxial in-plane and out-of-plane anisotropies [3]. This preferential Mn distribution is due to the fact that the nearest-neighbor Mn pair on the GaAs (001) surface has a lower energy for the [11(_)0] axis than the [110] case. However, such a preferential Mn distribution probably will not occur when the material is not grown in a layer-by-layer mode but by a liquid-phase-epitaxy-like process with the growth speed of meters per second, as for the case of ion implantation and pulsed laser melting (II-PLM) [4]. In this work, three typical III-Mn-V DFSs [(In,Mn)As, (Ga,Mn)As, and (Ga,Mn)P] are obtained through II-PLM. We find that both (Ga,Mn)P and (Ga,Mn)As samples exhibit the easy behavior in plane (as shown in Fig. 1) while the (In,Mn)As one reveals perpendicular magnetic anisotropy (not shown). The latter is attributed to the lattice strain due to lattice mismatch between the film and the substrate. The in-plane uniaxial anisotropy is much weakened for (Ga,Mn)P and (Ga,Mn)As from the magnetic hysteresis at 5 K. However, as shown in the inset to Fig. 1, the anisotropy changes with temperature increasing. More experimental results including magnetic hysteresis at different temperatures will be discussed during the conference.

Figure 1: Magnetic hysteresis along different crystalline axis for (Ga,Mn)P and (Ga,Mn)As with different Mn concentration measured at 5 K. The inset shows the magnetic remanence along different crystalline axis for the corresponding sample.
[1] M. Sawicki et al., Phys. Rev. B 70, 245325 (2004).
[2] C. Bihler et al., Phys. Rev. B 78, 045203 (2008).
[3] M. Birowska, et al., Phys. Rev. Lett. 108, 237203 (2012).
[4] M. A. Scarpulla et al., Appl. Phys. Lett. 82, 1251-1253 (2003).