High Curie temperature ferromagnetism in self-organized Ge1‑xMnx nano-columns

Thibaut Devillers 1Matthieu Jamet 1Andre Barski 1Romain Dujardin 1Valier Poydenot 1Pascale Bayle Guillemaud 1Johan Rothman 4Edith Bellet-Amalric 1Alain Marty 1Joël Cibert 3R. Mattana 2Serge Tatarenko 4

1. CEA Grenoble, Département de Recherche Fondamentale sur la Matière Condensée/SP2M, Grenoble 38054, France
2. Unité Mixte de Physique CNRS/Thales associée à l'Université Paris-Sud, Domaine de Corbeville, Orsay 91404, France
3. Laboratoire Louis Néel, CNRS (LLN), 25 Av. des Martyrs, Grenoble 38042, France
4. Laboratoire de Spectrométrie Physique - CNRS UMR 5588 (SPECTRO), Université J. Fourier, BP87, Saint Martin d'Hères 38402, France

Abstract

Room temperature ferromagnetic semiconductors, compatible with the silicon technology is one of the major challenges in the spintronic research. In this work, we show that, grown by molecular beam epitaxy (MBE), Mn-doped Ge, with a mean manganese content of 6%, exhibits ferromagnetic ordering over 400K. Structural and chemical analyses performed using Transmission Electron Microscopy (TEM) and Energy Electron Loss Spectroscopy (EELS) revealed strong non-homogeneities of Mn distribution in our MBE grown GeMn samples. Growth process induces the segregation of Mn and formation of Mn rich nanocolumns surrounded by a nearly pure Ge matrix. The average diameter of nano-columns is 3 nm and the average distance between nanocolumns is about 10 nm. This indicates that the concentration of manganese in nanocolumns is about 30% which is an unknown phase of the GeMn into the binary phase diagram of GeMn. The magnetic properties of our GeMn films grown on Ge (001) were investigated with a superconducting quantum interference device (SQUID). Magnetization measurements revealed a Curie temperature higher than 400K. The zero-field cooled (ZFC) and field cooled (FC) SQUID investigations exclude the presence in our GeMn films of the GeMn clusters and of the known stables phases of GeMn: Ge3Mn5 or Ge8Mn11. Magneto-transport measurements evidence a pronounced anomalous Hall effect and confirm: (i) p-type character of our GeMn layers, and (ii) pronounced holes spin-polarization.

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Presentation: Poster at E-MRS Fall Meeting 2006, Symposium E, by Thibaut Devillers
See On-line Journal of E-MRS Fall Meeting 2006

Submitted: 2006-05-12 13:44
Revised:   2009-06-07 00:44
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