Magnetic Interactions in Ge/1-x/Cr/x/Te Semimagnetic Semiconductors

TL;DR

This study investigates the magnetic properties of Ge/1-x/Cr/x/Te semiconductors, revealing spin-glass and ferromagnetic phases, and highlights the role of carrier-mediated RKKY interactions and Cr ion behavior in magnetic ordering.

Contribution

It provides new insights into the magnetic phases and interactions in Ge/Cr/Te semiconductors, including the effects of Cr concentration and spinodal decomposition.

Findings

Spin-glass state observed at low Cr concentrations (x=0.016, 0.025).

Ferromagnetic phase appears at higher Cr concentrations (x ≥ 0.030).

RKKY interaction explains magnetic behavior for x < 0.04.

Abstract

We present the studies of magnetic properties of Ge/1-x/Cr/x/Te diluted magnetic semiconductor with changeable chemical composition 0.016 \leq x \leq 0.061. A spin-glass state (at T \leq 35 K) for x = 0.016 and 0.025 and a ferromagnetic phase (at T < 60 K) for x \geq 0.030 are observed. The long range carrier-mediated magnetic interactions are found to be responsible for the observed magnetic ordering for x < 0.045, while for x \geq 0.045 the spinodal decomposition of Cr ions leads to a maximum and decrease of the Curie temperature, TC, with increasing x. The calculations based on spin waves model are able to reproduce the observed magnetic properties at a homogeneous limit of Cr alloying, e.g. x < 0.04, and prove that carrier mediated Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction is responsible for the observed magnetic states. The value of the Cr-hole exchange integral, Jpd, estimated via fitting of the experimental results with the theoretical model, is in the limits 0.77...0.88 eV.