Orientation Dependent Spin-Lattice Relaxation in CdMnSe

Abstract

The magnetization dynamics of Cd1-x Mnx Se at 4.5 K as a function of magnetic field up to 22 T was measured using a nonresonant technique. For x = 0.01 the relaxation does not depend on orientation and in higher fields the relaxation rates are proportional to B3 . For x = 0.02 a dependence on orientation is observed. The difference does not depend on magnetic field. This suggests that either the interaction between Mn ions responsible for spin-lattice relaxation in Mn clusters is anisotropic, or the relaxing clusters are oriented in a given manner with respect to the c axis.PACS numbers: 76.30.Fc, 63.20.Dj Using the nonresonant technique described earlier [1], we measured the magnetization dynamics in Cd1-xMnxSe at 4.5 K as a function of magnetic field. Two different compositions were investigated, namely x = 0.01 and x = 0.02. The measurements were done for external magnetic field B both: parallel and perpendicular to the c axiS (the CdSe host crystal, as well as mixed CdMnSe crystals, has a wurtzite structure). YAG:Nd laser pulses (λ = 1.06 pm) of 10 ns duration were used to create the thermal inequilibrium between spins and the lattice [1], rising lattice temperature. The spins then warm up to reach thermal equilibrium with the "warm" lattice. It causes the magnetization changes which are detected with a pick-up coil.The measured spin-lattice relaxation (SLR) rates are dependent on the external magnetic field, temperature, and composition. For lower Mn composition the data do not show any orientation dependence. In low magnetic field the relaxation rates (RR) weakly increase with B. In higher fields their dependence is not in contradiction with expected B3 dependence (see Fig. 1). Such a magnetic field de-