Relaxation of spin-glass magnetization in Cd1-xMnxTe diluted magnetic semiconductors

Relaxation of thermal-remanent magnetization and isothermal remanent magnetization of spin glass in Cd1-xMnxTe diluted magnetic semiconductors have been studied at different conditions. Magnetization relaxation can be described by a power-law decay, M(t)=M0t-α (t>t0 and t0=2 s) with small values of α or a logarithmic decay M(t)=M0(1-α lnt) (t>t0 and t0=2 s). Temperature and applied magnetic-field dependencies of the decay parameter α have been measured. The above-band-gap photoexcitation has been used to generate free carriers (electrons and holes) in the sample and their effects on the spin-spin interaction of Mn ions have been studied. The dependence of the power-law decay parameter α on excitation light intensity has also been measured. It is found that α is proportional to the photogenerated carrier concentration. Furthermore, aging effects in the spin-glass state have also been studied by varying the time duration of the applied magnetic field. The transient responses of magnetization in the spin-glass state upon applying a magnetic field in the dark and under illumination have been measured and are found to follow a power-law time dependence, M(t)=M0+M1tβ. Temperature and the applied magnetic-field dependencies of the transient parameter β have been measured. A mechanism, involving an increased spin domain size under light illumination via free-carrier-Mn spin interaction, can explain our results very well.