Magnetization of ultrathin (Ga,Mn)As layers

TL;DR

This study investigates the magnetic properties of ultrathin (Ga,Mn)As layers, revealing how thickness and annealing influence Curie temperature and Mn atom distribution, with implications for spintronic applications.

Contribution

It provides new insights into how ultrathin (Ga,Mn)As layers' magnetic properties change with thickness and annealing, highlighting Mn segregation effects.

Findings

Thinner layers show different magnetic microstructures.

Annealing increases Curie temperature in ultrathin layers.

Mn displacement occurs upon annealing, affecting magnetic properties.

Abstract

Kerr rotation and Superconducting QUantum Interference Device (SQUID) magnetometry measurements were performed on ultrathin (Ga$_{0.95}$Mn$_{0.05}$)As layers. The thinner layers (below 250 \AA) exhibit magnetic properties different than those of thicker ones, associated with different microstructure, and some degree of inhomogeneity. The temperature dependence of the field-cooled-magnetization of the layers is recorded after successive low temperature annealings. While the Curie temperature of the thicker layer (250 \AA) is nearly unchanged, the critical temperature of the thinner layers is enhanced by more than 23 K after two annealings. Secondary Ion Mass Spectrometry (SIMS) experiments on similar layers show that Mn is displaced upon annealing. The results are discussed considering a possible segregation of substitutional and interstitial Mn atoms at the surface of the (Ga,Mn)As layers.