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Magnetic ordering and exchange interactions in structural modifications of Mn3Ga alloys: Interplay of frustration, atomic order, and off-stoichiometry

Sergii Khmelevskyi, Andrei V. Ruban, and Peter Mohn
Phys. Rev. B 93, 184404 – Published 4 May 2016

Abstract

Mn-Ga alloys close to the Mn3Ga stoichiometry can be synthesized in three different crystal modifications: hexagonal, tetragonal, and face-centered cubic, both in bulk and in thin-film forms. The magnetic ordering of these modifications is varying from noncollinear antiferromagnetic in the hexagonal case to ferrimagnetic order in the tetragonal one, whereas it is still unknown for the atomically disordered fcc structure. Here we study the onset of magnetic order at finite temperatures in these systems on a first-principles basis calculating the interatomic magnetic exchange interactions in the high-temperature paramagnetic regime. We employ the disordered local moment formalism and the magnetic force theorem within the framework of the local spin-density approximation and Monte Carlo simulations taking also the effects of atomic disorder in fcc alloys into account. In particular we find the origin of the stabilization of the noncollinear 3k structure in competition between antiferromagnetic inter- and in-plane couplings of frustrated kagome planes in hexagonal Mn3Ga and predict the antiferromagnetic-1 collinear order due to frustration in fcc alloys. Special attention is paid to the effects of the off-stoichiometry and the consequences of atomic disorder. We calculate the site-preference energy of Ga antisite atoms in the tetragonal structures in the range of the compositions from Mn3Ga to Mn2Ga and slightly beyond and confirm the earlier explanation of the effect of magnetization increase due to Ga preferentially occupying one of the Mn sites.

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  • Received 24 February 2016
  • Revised 13 April 2016

DOI:https://doi.org/10.1103/PhysRevB.93.184404

This article is available under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.

Published by the American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Sergii Khmelevskyi1, Andrei V. Ruban2, and Peter Mohn1

  • 1Center for Computational Materials Science, Institute for Applied Physics, Vienna University of Technology, Wiedner Hauptstrasse 8, A-1040 Vienna, Austria
  • 2Department of Materials Science and Engineering, Royal Institute of Technology, 10044 Stockholm, Sweden

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Issue

Vol. 93, Iss. 18 — 1 May 2016

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