Magnetochemical origin for Invar anomalies in iron-nickel alloys

V. Crisan; P. Entel; H. Ebert; H. Akai; D. D. Johnson; J. B. Staunton

doi:10.1103/PhysRevB.66.014416

Magnetochemical origin for Invar anomalies in iron-nickel alloys

V. Crisan, P. Entel, H. Ebert, H. Akai, D. D. Johnson, and J. B. Staunton

Phys. Rev. B 66, 014416 – Published 8 July 2002

Abstract

Zero- and finite-temperature (T) first-principles calculations versus composition (c) show that magnetochemical effects lead to Invar anomalies in Fe-(Ni, Co, Pt) alloys. Chemical short- or long-range order and negative interatomic exchange interaction of electrons in antibonding majority-spin states force the face-centered-cubic lattice to compete simultaneously for a smaller volume (from antiferromagnetic tendencies) and a larger volume (from Stoner ferromagnetic tendencies). The resulting additional negative lattice anharmonicity is very large for Fe-(Ni, Co) while absent for Fe-Pt. Our results explain the T- and c-dependent behavior of Invar properties, including the lattice softening and thermal expansion of Fe-Ni. In addition, the occurrence of a noncollinear spin structure at $T = 0 K$ near Invar can be understood on the basis of our results.

Received 13 June 2001

DOI:https://doi.org/10.1103/PhysRevB.66.014416

Authors & Affiliations

V. Crisan^1,*, P. Entel^1,†, H. Ebert^2,‡, H. Akai^3,§, D. D. Johnson^4,∥, and J. B. Staunton^5,¶

¹Theoretical Physics, Gerhard-Mercator University, Lotharstraße 1, 47048 Duisburg, Germany
²Institute for Physical Chemistry, Ludwig-Maximilians University, Butenandtstraße 5-13, 81377 München, Germany
³Department of Physics, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
⁴Department of Materials Science and Engineering, University of Illinois, Urbana, Illinois 61801
⁵Department of Physics, University of Warwick, Coventry CV4 7AL, United Kingdom

^*Permanent address: Department of Physics, Babes-Bolyai University, Kogalniceanu 1, 3400 Cluj-Napoca, Romania. Email address: crisan@thp.uni-duisburg.de
^†Email address: entel@thp.uni-duisburg.de
^‡Email address: hubert.ebert@cup.uni-muenchen.de
^§Email address: akai@phys.sci.u-osaka.ac.jp
^∥Email address: duanej@uiuc.edu
^¶Email address: j.b.staunton@warwick.ac.uk

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Vol. 66, Iss. 1 — 1 July 2002

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