Magnetic Interactions and Magnetotransport in Ge1-X TM x Te Diluted Magnetic Semiconductors

Abstract

Diluted magnetic semiconductors (DMS) allows an independent control of electrical and magnetic properties by many orders of magnitude via changes in the technological parameters of the growth or post growth treatment of the compound. DMS compounds are usually developed on the basis of a III−V or II−VI semiconductor matrix into which transition metal (TM) or rare earth ions are introduced on a level of several atomic percent. IV−VI based DMS, in particular Ge1-x TM x Te alloys, possess many advantages over widely studied Ga1-x Mn x As. The carrier concentration and the amount of TM ions can be controlled independently. Moreover, the solubility of TM ions in GeTe is very high allowing growth of homogeneous Ge1-x TM x Te solid solutions over a wide range of chemical composition. Itinerant ferromagnetism can be controlled in a wide range of values reaching the Curie temperatures with a maximum of about 200 K for bulk Ge1-x Mn x Te with x = 0.5. The most important aspects of the current progress in understanding the structural, electrical, and magnetic properties of the selected representatives of Mn- and Cr-alloyed GeTe based DMS systems are reviewed. The present state of the studies of the physical mechanisms of the ferromagnetism and spin-glass-like states in Ge1-x TM x Te are described as well as the explanation of the nature of the magnetotransport effects such as negative magnetoresistance and anomalous Hall effect in Ge1-x TM x Te solid solutions.