Spin‐lattice relaxation in diluted magnetic semiconductors

The contribution of pairs and triads of nearest‐neighbor spins to the spin‐lattice relaxation of magnetization is evaluated in Mn‐based diluted magnetic semiconductors. Modulation of the exchange interaction by lattice vibrations allows transitions in the cluster which change the total magnetization when the Dzyaloshinski‐Moriya interaction is taken into account. Spin‐lattice relaxation rates are calculated for pairs and open triads due to a two‐phonon Orbach process. In Cd1−xMnxTe it is found that the main contribution to relaxation of magnetization comes from triads. For temperatures ranging from 10 to 35 K and for x between 0.002 and 0.02 relaxation of triads can account very well for the observed relaxation rates, if one assumes rapid spin diffusion. Fitting of the experimental data yields an approximate value of a = J/(dJ/dr) ∼ 0.35 A, where J is the nearest‐neighbors exchange constant and r the Mn‐anion bond length, in good agreement with the expected value for a superexchange interaction.