Thickness dependence of magnetic properties of (Ga,Mn)As

TL;DR

This study investigates how reducing the thickness of (Ga,Mn)As affects its magnetic properties, revealing a decrease in Curie temperature and a spin reorientation transition, with implications for spintronics device design.

Contribution

It demonstrates the thickness-dependent magnetic behavior of (Ga,Mn)As and models the effects considering defect gradients and surface traps within the p-d mean field Zener framework.

Findings

Curie temperature decreases monotonically with thinning

Spin reorientation transition occurs during thinning

Model explains effects via defect gradients and surface traps

Abstract

We report on a monotonic reduction of Curie temperature in dilute ferromagnetic semiconductor (Ga,Mn)As upon a well controlled chemical-etching/oxidizing thinning from 15 nm down to complete removal of the ferro- magnetic response. The effect already starts at the very beginning of the thinning process and is accompanied by the spin reorientation transition of the in-plane uniaxial anisotropy. We postulate that a negative gradient along the growth direction of self-compensating defects (Mn interstitial) and the presence of surface donor traps gives quantitative account on these effects within the p-d mean field Zener model with adequate mod- ifications to take a nonuniform distribution of holes and Mn cations into account. The described here effects are of practical importance for employing thin and ultrathin layers of (Ga,Mn)As or relative compounds in concept spintronics devices, like resonant tunneling devices in particular.