Saturated Ferromagnetism and Magnetization Deficit in Optimally Annealed (Ga,Mn)As Epilayers

TL;DR

This study investigates how Mn concentration affects the magnetic and electronic properties of optimally annealed GaMnAs epilayers, revealing saturation in certain properties and a decline in ferromagnetic participation at higher Mn levels.

Contribution

It provides new insights into the Mn concentration dependence of magnetic and electronic properties in GaMnAs, highlighting the saturation of Tc and conductivity and the decrease in ferromagnetic moment per Mn at higher concentrations.

Findings

Curie temperature and conductivity increase with Mn up to x ~ 0.05, then plateau.

Ferromagnetic moment per Mn decreases monotonically with increasing x.

Domain wall thickness remains constant despite changes in Mn concentration.

Abstract

We examine the Mn concentration dependence of the electronic and magnetic properties of optimally annealed Ga1-xMnxAs epilayers for 1.35% < x < 8.3%. The Curie temperature (Tc), conductivity, and exchange energy increase with Mn concentration up to x ~ 0.05, but are almost constant for larger x, with Tc ~ 110 K. The ferromagnetic moment per Mn ion decreases monotonically with increasing x, implying that an increasing fraction of the Mn spins do not participate in the ferromagnetism. By contrast, the derived domain wall thickness, an important parameter for device design, remains surprisingly constant.