Magneto-Optical Detection of the Intrinsic Ferromagnetism and Phase Separation in Diluted Magnetic Semiconductors

Spectral and temperature dependences of the magneto-optical transversal Kerr effect (TKE) of GaMnAs layers prepared by different methods are reported in this work. The GaMnAs layers prepared by pulsed laser sputtering at 300 degrees C demonstrate a ferromagnetic behavior below 80 K, which is due to the presence of local ferromagnetic (Ga,Mn)As areas in the paramagnetic matrix. The Ga(In)MnAs layers prepared by ion implantation and subsequent pulsed laser annealing were found to exhibit a high TKE response at low temperatures. The presence of the characteristic band in the TKE spectrum in the range of transitions near the L point of the band structure of Ga(In)As confirms the intrinsic ferromagnetism. The temperature dependences of TKE measured for different spectrum ranges demonstrate nonmonotonic behavior, which indicates the magnetic inhomogeneity of the layers. The peculiarities of the magneto-optical spectra of GaMnAs, which were not observed previously, were explained by taking the magnetic and phase inhomogeneity of the layers into account. The sensitivity of TKE to the phase inhomogeneity of the Ga(In)MnAs layers and the efficiency of TKE in studying the electron spectrum and magnetic structure of diluted magnetic superconductors are demonstrated.