Spin‐lattice relaxation in diluted magnetic semiconductors

Abstract

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-Monya interaction is taken into account. Spin-lattice relaxation rates are calculated for pairs and open triads due to a two-phonon Orbach process. In Cdl_,Mn,Te 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) M 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.

Spin–lattice relaxation in diluted magnetic (Cd,Mn)Se quantum dots

“…In Table 1, this time constant is compared with those measured by the same technique on (Zn,Cd,Mn)Se QWs. The QW data reflect the expected tendency that the SLR rate grows exponentially with the Mn content, caused by the contribution of Mn pairs and higher complexes in the coupling of the Mn spins to the lattice [11]. We emphazise that the values observed on the quarternary (Zn,Cd,Mn)Se QWs match well with data reported for (Zn,Mn)Se QWs [12].…”

Spin-lattice relaxation of Mn ions inZnMnSe∕ZnBeSequantum wells measured under pulsed photoexcitation

“…The SLR rate is a strong function of the lattice temperature [12], and it decreases weakly in magnetic fields B below 12 T [8-10, 6] but increases rapidly (…”

Spin diffusion in theMn2+ion system of II-VI diluted magnetic semiconductor heterostructures

“…1(c) 6,8 . Such a strong dependence is explained by the role of Mn clusters as relaxation centers 9 in the absence of SLR for isolated Mn ions. With increasing Mn concentration the number of clusters grows and the cluster structure evolutes in size involving more and more spins.…”

“…Both the number of Mn spins coupled in clusters as well as the typical cluster size progressively increase with growing Mn concentration 22 . This is the reason for the strong dependence of the SLR time on the Mn concentration 9,23,24 . Within the framework of a simple model which accounts for the spin diffusion from Mn ions to Mn clusters, where the spin has an efficient relaxation, it can be shown that the SLR rate 1/τ SLR has a strong dependence on the Mn content with a power law between x 3 and x 4 [11].…”