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Posted: Jan 22, 2018
Magnetic semiconductor layers of a new type
(Nanowerk News) Researchers at the laboratory of spin and optical electronics of the Lobachevsky University (Nizhny Novgorod, Russia) have obtained a new type of magnetic semiconductor layers, which demonstrate spin-dependent phenomena in the transport of charge carriers at room temperature (Journal of Applied Physics, "High-temperature intrinsic ferromagnetism in the (In,Fe)Sb semiconductor").
It is well known that in magnetic semiconductors the current is conducted by means of spin-polarized charge carriers, which offers additional possibilities for creating information- processing devices based on the use of both the electron charge and its spin. For practical implementation of spintronic semiconductor devices, magnetic semiconductors operating at room Curie temperature are required.
Using pulsed laser deposition, Nizhny Novgorod scientists have fabricated (In,Fe)Sb epitaxial layers with Fe content up to 13 atomic % on GaAs substrates. These layers exhibit ferromagnetic properties up to room temperature. In the (In,Fe)Sb layers, characteristic spin-dependent electron transport phenomena were observed at room temperature, including the anomalous Hall effect and the hysteresis negative magnetoresistance.
This indicates that conduction electrons in the synthesized semiconductor have spin polarization at room temperature, i.e. most electrons have a common spin direction, similar to what happens in a ferromagnetic metal. The new magnetic semiconductor's unique feature is that its ferromagnetism is intrinsic, associated with the formation of a spin-split band structure.
This, in particular, is manifested in spin-dependent optical transitions in the band structure of the semiconductor and phase homogeneity of the material. In turn, intrinsic ferromagnetism is a necessary condition for using semiconductor ferromagnetic materials, since it provides spin-dependent optical and transport properties of the semiconductor.
Low Curie temperature of magnetic semiconductors is a serious limitation on the way of their practical use. For the first time, the Curie temperature exceeding the room temperature was achieved for the material (In,Fe)Sb obtained by Lobachevsky University scientists.