p-type codoping effect in (Ga,Mn)As: Mn lattice location versus magnetic properties

TL;DR

This study investigates how p-type codoping with Zn affects the magnetic properties of (Ga,Mn)As, revealing that increased hole concentration can lead to decreased Curie temperature and a transition from ferromagnetism to paramagnetism due to Mn site shifts.

Contribution

It provides new insights into the effects of Zn codoping on Mn lattice location and magnetic properties in (Ga,Mn)As, supported by experimental and first-principles calculations.

Findings

Increased Zn doping raises hole concentration but decreases Curie temperature.

Mn atoms shift from substitutional to interstitial sites with Zn doping.

A phase transition from ferromagnetism to paramagnetism occurs with higher hole concentration.

Abstract

In the present work, we perform a systematic investigation on p-type codoping in (Ga,Mn)As. Through gradually increasing Zn doping concentration, the hole concentration increases, which should theoretically lead to an increase of the Curie temperature (TC) according to the p-d Zener model. Unexpectedly, although the film keeps its epitaxial structure, both TC and the magnetization decrease. The samples present a phase transition from ferromagnetism to paramagnetism upon increasing hole concentration. In the intermediate regime, we observe a signature of antiferromagnetism. By using channeling Rutherford backscattering spectrometry and particle-induced x-ray emission, the substitutional Mn atoms are observed to shift to interstitial sites, while more Zn atoms occupy Ga sites, which explains the observed behavior. This is also consistent with first-principles calculations, showing that the complex of substitutional Zn and interstitial Mn has the lowest formation energy.