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

Abstract

Relaxation of thermal-remanent magnetization and isothermal remanent magnetization of spin glass in ${\mathrm{Cd}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Mn}}_{\mathit{x}}$Te diluted magnetic semiconductors have been studied at different conditions. Magnetization relaxation can be described by a power-law decay, M(t)=${\mathit{M}}_{0}$${\mathit{t}}^{\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\alpha}}}$ (tg${\mathit{t}}_{0}$ and ${\mathit{t}}_{0}$=2 s) with small values of \ensuremath{\alpha} or a logarithmic decay M(t)=${\mathit{M}}_{0}$(1-\ensuremath{\alpha} lnt) (tg${\mathit{t}}_{0}$ and ${\mathit{t}}_{0}$=2 s). Temperature and applied magnetic-field dependencies of the decay parameter \ensuremath{\alpha} 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 \ensuremath{\alpha} on excitation light intensity has also been measured. It is found that \ensuremath{\alpha} 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)=${\mathit{M}}_{0}$+${\mathit{M}}_{1}$${\mathit{t}}^{\mathrm{\ensuremath{\beta}}}$. Temperature and the applied magnetic-field dependencies of the transient parameter \ensuremath{\beta} 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.