Is it possible to create magnetic semiconductors that work at room temperature?

Abstract

Ferromagnetic semiconductors combine the properties of both ferromagnetic and semiconducting systems at the material level. Comparing with ferromagnetic metals, an obvious advantage of a ferromagnetic semiconductor is the great tunability of its magnetic properties via variation of its carrier density by nonmagnetic means, such as electrostatic gating or photoillumination. Over the past two decades, the ferromagnetic semiconductor has attracted much attention and developed into an important branch of condensed matter physics and materials sciences. Many kinds of important spintronic functionalities have been realized based on ferromagnetic semiconductors, like the electrical-field control of the Curie temperature and the magnetization, spin injection into nonmagnetic semiconductors, tunneling magnetoresistance, and electric current-induced magnetization reversal. Unfortunately, all these performances have been demonstrated only at low temperatures but not yet in a range warm enough for practical applications. However, room-temperature operation is a prerequisite for spintronic applications. Scientists have devoted themselves to making nonmagnetic semiconductors ferromagnetic at room temperature. Research in this direction has never been stopped. This article firstly introduces the concept of magnetic semiconductor, then provides a brief introduction of possible inside mechanisms of so-called room-temperature ferromagnetic semiconductors, such as ZnO and GaN doped with Mn, and then focuses on the recent progress of typical magnetic semiconductor (Ga, Mn)As, which is widely adopted to be with intrinsic ferromagnetism. Finally, the article provides an outlook on the possibility of creating room-temperature ferromagnetic semiconductors.