Effect of annealing on magnetic properties of new (In,Al,Mn)As ferromagnetic semiconductors

The molecular beam epitaxial growth and effect of low-temperature annealing on magnetic properties of (In, Al, Mn)As, a new type of ferromagnetic semiconductor, are reported. The growth is monitored in situ with the reflection high energy electron diffraction (RHEED), and a (2×4) pattern is observed for the (In, Al)As buffer layers, while change to (1×n) during and after growth of (In, Al, Mn)As epilayer. The post-growth annealing is performed at 210, 230, 250, 270, and 290°C for 2 hours in air. Magnetization curves confirm that all samples show a ferromagnetic state at 5 K. It should be noted that the coercivity of (In, Al, Mn)As is much lower than those of (Ga, Mn)As and (In, Ga, Mn)As. The Curie temperature T_C is observed to increase with increasing annealing temperature when T<250°C and then decrease with temperature when T>250°C.