Spin dynamics in paramagnetic diluted magnetic semiconductors

Microscopic properties of low-energy spin dynamics in diluted magnetic semiconductor are addressed in a framework of the Kondo lattice model including random distribution of magnetic dopants. Based on the fluctuation-dissipation theorem, we derive an explicit dependence of the spin diffusion coefficient on the single-particle Green function which is directly evaluated by dynamical mean-field theory. In the paramagnetic state, the magnetic scattering has been manifested to suppress spin diffusion. In agreement with other ferromagnet systems, we also point out that the spin diffusion in diluted magnetic semiconductors at small carrier concentration displays a monotonic $1/T$-like temperature dependence. By investigating the spin diffusion coefficient on a wide range of the model parameters, the obtained results have provided a significant scenario to understand the spin dynamics in the paramagnetic diluted magnetic semiconductors.

Figure 1

$D_s\chi$ vs carrier concentration $n$ at $J=3, U=0.5$, and $T=0.1$ for some densities $x$ of magnetic impurities.

Figure 2

The dependence of $D_s\chi$ on $x$ at $J=3, U=0.5$, and $T=0.1$ for different values of $n$.

Figure 3

Dependence of $D_s\chi$ on $J$ at $U=0.5, x=0.1$, and $T=0.1$ for different values of $n$. The inset shows the DOS of itinerant carriers $A\left(\omega \right)$ at $J=0.5$ for the same different values of $n$ mentioned in the main panel, plotted in the same line styles. Here a vertical dashed-line denotes the Fermi level.

Figure 4

Dependence of $D_s\chi$ on temperature at $J=3, x=0.1$, and $U=0.5$ for different values of $n$.