Effect of spin-glass order on magnetic polarons in semimagnetic semiconductors

TL;DR

This paper develops a theoretical framework to understand how spin glass order influences magnetic polarons in semiconductors, revealing new effects on their energy and formation dynamics, and fitting experimental data.

Contribution

We introduce a self-consistent theory for magnetic polarons in spin glass phases, incorporating exchange fields and analyzing temperature effects and dynamics.

Findings

Spin glass order causes a plateau in MP energy at low temperatures.

The model fits experimental data on (Cd,Mn)Te exciton magnetic polaron energy.

Different dynamical scenarios predict distinct temperature dependences of MP formation time.

Abstract

A theory accounting for the specific features of magnetic polarons (MP) in the presence of spin glass order is presented. We derive and solve selfconsistent equations for i) the polaron magnetisation, ii) the thermodynamically averaged carrier--spin, and iii) for the spin glass order parameter. The temperature dependence of these quantities is analysed in detail. The modification of the spin glass phase due to the presence of the exchange field of the carrier inside the magnetic polaron volume is investigated. The onset of spin glass order leads to a plateau--like flattening in the temperature dependence of the MP energy at low temperatures. It is found that solutions of spin glass equations are needed to optimally fit the experimental data of the temperature dependence of the exciton magnetic polaron (EMP) energy in (Cd,Mn)Te. Moreover, the dynamical aspects of the MP formation are discussed. Our model predicts qualitatively different temperature dependences of the MP formation time in different dynamical scenarios.