Diluted magnetic semiconductors: An interface of semiconductor physics and magnetism (invited)

TLDR

Diluted magnetic semiconductors are ternary alloys containing substitutional magnetic ions such as Mn in CdTe or HgTe, whose composition‑dependent band gap and effective mass, together with magnetic phenomena like spin‑glass transitions and magnon excitations, are modified by strong exchange coupling between localized moments and band carriers, profoundly affecting band structure, impurity states, transport, and magneto‑optical properties. This review surveys the electrical, magnetic, and optical characteristics of diluted magnetic semiconductors. The authors synthesize and analyze experimental data on these materials, discussing how substitutional magnetic ions influence carrier dynamics and optical responses. Exchange interactions in these alloys produce extremely large, temperature‑dependent g‑factors, gigantic Faraday rotation, pronounced negative magnetoresistance, and the formation of bound magnetic polarons.

Abstract

This paper reviews the electrical, magnetic, and optical properties of diluted magnetic semiconductors (sometimes also referred to as ‘‘semimagnetic’’ semiconductors). These materials are ternary semiconductor alloys whose lattice is made up in part of substitutional magnetic ions. Cd1−xMnxTe and Hg1−xMnxTe are examples of such systems. As semiconductors, these alloys display interesting and important properties, such as the variation of the energy gap and of effective mass with composition. They also exhibit magnetic properties which are interesting in their own right, e.g., a low temperature spin glass transition and magnon excitations. Most importantly, however, the presence of substitutional magnetic ions in these alloys leads to spin–spin exchange interaction between the localized magnetic moments and the band electrons. This in turn has rather important consequences on band structure and on donor and acceptor states, leading to dramatic effects in quantum transport, impurity conduction, and magneto-optics. Specifically, the presence of exchange interaction results in extremely large and temperature dependent g-factors of electrons and holes; in gigantic values of Faraday rotation; in anomalously large negative magnetoresistance; and in the formation of the bound magnetic polaron.