Ferromagnetic nature of (Ga, Cr)As epilayers revealed by magnetic circular dichroism

A systematic study of magnetic circular dichroism (MCD) was carried out in a wave length range 500–960 nm for (Ga1−x, Crx)As epilayers with x = 2.38 % and 4.59 % grown by the low temperature molecular beam epitaxy (LT-MBE) technique. Hysteresis characteristics showed up indeed in the magnetic field dependence of both MCD and magnetization measured by the superconductor quantum interference device (SQUID). The Curie temperature of the (Ga1−x, Crx)As epilayer was determined to be about 12 K by the Arrott approach. The present result provides evidences that there is strong coupling of the Cr spins to the GaAs host band structure in (Ga1−x, Crx)As samples. That affects the critical point of the semiconductor host, and makes the magnetization behavior in a plot of M ∼ B / T (magnetic field divided by temperature) substantially different from standard superparamagnetism.