New evidence for structural and magnetic properties of GaAs:(Mn,Ga)As granular layers

TL;DR

This study investigates the structural and magnetic properties of GaAs:(Mn,Ga)As layers with nanoclusters, revealing different cluster types, strain variations, and ferromagnetic behavior at room temperature, advancing understanding of magnetic semiconductor nanostructures.

Contribution

It provides new evidence on the types of nanoclusters present and their magnetic properties, especially the ferromagnetic coupling of Mn ions within cubic (Mn,Ga)As clusters at room temperature.

Findings

Two types of nanoclusters detected with different structures.

Only cubic (Mn,Ga)As clusters identified, no MnAs cubic phase.

Ferromagnetic coupling of Mn ions persists at room temperature.

Abstract

Structural and magnetic properties of GaAs thin films with embedded MnAs nanoclusters were investigated as function of the annealing temperature and layers composition. The presence of two kinds of nanoclusters with different dimensions and structure were detected. The fraction of Mn atoms in each kind of cluster was estimated from the extended X-ray absorption fine structure analysis. This analysis ruled out the possibility of the existence of nanoclusters containing a hypothetic MnAs cubic compound - only (Mn,Ga)As cubic clusters were detected. Change of the layer strain from the compressive to tensile was related to the fraction of zinc blende and hexagonal inclusions. Thus the zinc blende inclusions introduce much larger strain than hexagonal ones. The explanation of observed thermal induced strain changes of the layers from the compressive to tensile is proposed. The magnetic properties of the samples were consistent with structural study results. Their showed that in sample containing solely cubic (Mn,Ga)As inclusions Mn ions inside the inclusions are still ferromagnetically coupled, even at room temperature. This fact can be explained by existence in these clusters of GaMnAs solid solution with content of Mn higher than 15 % as was found in theoretical calculations.