Interfacial structure and half-metallic ferromagnetism in Co2MnSi-based magnetic tunnel junctions

N. D. Telling, P. S. Keatley, G. van der Laan, R. J. Hicken, E. Arenholz, Y. Sakuraba, M. Oogane, Y. Ando, and T. Miyazaki
Phys. Rev. B 74, 224439 – Published 28 December 2006

Abstract

X-ray absorption (XAS) and x-ray magnetic circular dichroism (XMCD) techniques are utilized to explore the ferromagnetic/barrier interface in Co2MnSi full Heusler alloy magnetic tunnel junctions. Structural and magnetic properties of the interface region are studied as a function of the degree of site disorder in the alloy and for different degrees of barrier oxidation. Photoelectron scattering features that depend upon the degree of L21 ordering are observed in the XAS spectra. Additionally, the moments per 3d hole for Co and Mn atoms are found to be a sensitive function of both the degree of L21 ordering and the barrier oxidation state. Significantly, a multiplet structure is observed in the XMCD spectra that indicates a degree of localization of the moments and may result from the half-metallic ferromagnetism (HMF) in the alloy. The magnitude of this multiplet structure appears to vary with preparation conditions and could be utilized to ascertain the role of the constituent atoms in producing the HMF, and to examine methods for preserving the half-metallic state after barrier preparation. The changes in the magnetic structure caused by barrier oxidation could be reversed by inserting a thin Mg interface layer in order to suppress the oxidation of Mn in the Co2MnSi layer.

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  • Received 13 September 2006

DOI:https://doi.org/10.1103/PhysRevB.74.224439

©2006 American Physical Society

Authors & Affiliations

N. D. Telling1, P. S. Keatley2, G. van der Laan1, R. J. Hicken2, E. Arenholz3, Y. Sakuraba4, M. Oogane4, Y. Ando4, and T. Miyazaki4

  • 1Magnetic Spectroscopy Group, CCLRC Daresbury Laboratory, Warrington WA4 4AD, United Kingdom
  • 2School of Physics, University of Exeter, Stocker Road, Exeter EX4 4QL, United Kingdom
  • 3Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
  • 4Department of Applied Physics, Graduate School of Engineering, Tohoku University, Aoba-yama 6-6-05, Sendai 980-8579, Japan

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Issue

Vol. 74, Iss. 22 — 1 December 2006

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