Ferromagnetic transition induced by re-crystallization of amorphous (Ge,Mn)Te layers

Tomasz Story ,  Wojciech Knoff ,  Tomasz Andrearczyk ,  Wiktor Domuchowski ,  Piotr Dziawa ,  Leszek Kowalczyk ,  Elżbieta Łusakowska ,  Krzysztof Świątek ,  Badri Taliashvili ,  Jerzy Wróbel 

Polish Academy of Sciences, Institute of Physics, al. Lotników 32/46, Warszawa 02-668, Poland

Abstract

(Ge,Mn)Te is a IV-VI diluted magnetic (semimagnetic) semiconductor exhibiting ferromagnetic transition induced by a very high conducting hole concentration. The Curie temperature in crystalline (Ge,Mn)Te layers can be increased up to Tc=190 K by independently optimizing the Mn content and the carrier concentration. Amorphous (Ge,Mn)Te layers exhibit very high resistivity and show paramagnetic properties. In GeTe and (Ge,Mn)Te layers a very fast switching between amorphous and crystalline phases can be induced locally by laser beam, electron beam or electric current flow. We examine magnetic and structural properties of amorphous, polycrystalline (re-crystallized), and monocrystalline (Ge,Mn)Te layers with thickness of about one micron and Mn content up to 20 at. % grown on insulating BaF2 (111) substrates by molecular beam epitaxy technique. The local re-crystallization of amorphous layer was successfully achieved under the influence of light (YAG:Nd pulsed laser) and electron beam of a scanning electron microscope. Various micron-size wire-like patterns of a polycrystalline (Ge,Mn)Te embedded in an amorphous (Ge,Mn)Te matrix were prepared. Magnetic properties of (Ge,Mn)Te layers and wires were studied by superconducting magnetometry and ferromagnetic resonance (FMR) methods. The analysis of the temperature and magnetic field dependence of magnetization confirmed paramagnetic properties of amorphous layers and revealed a sharp ferromagnetic transition in polycrystalline (Ge,Mn)Te wires re-crystallized either by laser or by electron beam action. In re-crystallized (Ge,Mn)Te samples with Mn content of 10 at. %. the ferromagnetic Curie temperature is Tc=72 K. The analysis of the temperature and angular dependence of the FMR resonant field showed pronounced changes between the normal to the layer plane and various in-plane orientations of the magnetic field pointing out to the dominant role of magnetic shape anisotropy.

Work supported by the EC via ITN SemiSpinNet. 

 

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Presentation: Oral at E-MRS Fall Meeting 2009, Symposium E, by Tomasz Story
See On-line Journal of E-MRS Fall Meeting 2009

Submitted: 2009-05-11 10:39
Revised:   2009-07-01 12:53