Spin relaxation near a ferromagnetic transition

TL;DR

This paper investigates how spin relaxation mechanisms change near a ferromagnetic transition in dilute magnetic semiconductors, highlighting the roles of spin fluctuations, magnetic components, and different relaxation timescales.

Contribution

It introduces a detailed analysis of spin relaxation near a ferromagnetic transition, emphasizing the impact of strong spin fluctuations and multiple magnetic components.

Findings

Spin relaxation mechanism shifts from Dyakonov-Perel to spin flips near the transition.

Presence of two magnetic components causes different relaxation rates for magnetization and total spin.

Longer relaxation times are governed by spin-orbit interactions after initial redistribution.

Abstract

We study spin relaxation in dilute magnetic semiconductors near a ferromagnetic transition, where spin fluctuations become strong. An enhancement in the scattering rate of itinerant carriers from the spin fluctuations of localized impurities leads to a change in the dominant spin relaxation mechanism from Dyakonov-Perel to spin flips in scattering. On the ferromagnetic side of the transition, we show that due to the presence of two magnetic components -- the itinerant carriers and the magnetic impurities -- with different gyromagnetic ratios, the relaxation rate of the total magnetization can be quite different from the relaxation rate of the spin. Following a disturbance of the equilibrium magnetization, the spin is initially redistributed between the two components to restore the equilibrium magnetization. It is only on a longer time scale, controlled by the spin-orbit interaction, that the total spin itself relaxes to its equilibrium state.