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Ferromagnetic (Eu,Gd)Te/PbTe semiconductor heterostructures

Piotr Dziawa ,  Sylwia Wrotek ,  Wiktor Domuchowski ,  K. Dybko ,  Leszek Kowalczyk ,  Elżbieta Łusakowska ,  Andrzej Mąkosa ,  A. Morawski ,  Victor Osinniy ,  Badri Taliashvili ,  Zbigniew Tkaczyk ,  Tadeusz Wosiński ,  Jerzy Wróbel ,  Tomasz Story 

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


In n-(Eu,Gd)Te magnetic semiconductor alloys ferromagnetic ordering is driven by the RKKY interaction between magnetic moments of rare earth Eu2+ and Gd3+ ions. This material is expected to exhibit very high degree of electron spin polarization and serve as a ferromagnetic element of model all-semiconductor spintronic structures. In this work we discuss the growth and structural characterization of (Eu,Gd)Te/PbTe heterostructures and analyze their magnetic and electrical characteristics.

(Eu,Gd)Te/PbTe heterostructures were grown by molecular beam epitaxy on BaF2 (111) substrates. In situ reflection high-energy electron diffraction as well as ex situ x-ray diffraction and atomic force microscopy characterization proved high structural quality of both PbTe and (Eu,Gd)Te epitaxial layers. For magnetic characterization the measurements of magnetic hysteresis loops and the temperature dependence of magnetization of (Eu,Gd)Te/PbTe layers were carried out with SQUID magnetometer. In various n-(Eu,Gd)Te/PbTe layers ferromagnetic transition was found with the Curie temperature TC=11-15 K. The n-(Eu,Gd)Te/p-PbTe heterostructures were fabricated lithographically in the form of mesa structures with thick PbTe buffer layer serving as the bottom p-type electrode and the n-(Eu,Gd)Te top electrode with gold electrical contacts. For electrical characterization the I-V characteristics and the electrical conductance of the p-n heterostructures were examined as a function of temperature and magnetic field. The strongly non-linear I-V characteristics of such p-n heterojunctions were experimentally observed. In selected heterojunctions it was found that the junction electrical conductance is reduced (up to 30-60 %) below the Curie temperature. The external magnetic field of 600 Oe applied in layer plane also reduces the junction conductance (typically by 10%).

Work supported by KBN research project No. PBZ-KBN-044/P03/2001.


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Presentation: poster at E-MRS Fall Meeting 2005, Symposium D, by Piotr Dziawa
See On-line Journal of E-MRS Fall Meeting 2005

Submitted: 2005-06-01 08:52
Revised:   2009-06-07 00:44