Nonzero orbital moment in high coercivity ϵ-Fe2O3 and low-temperature collapse of the magnetocrystalline anisotropy

Yuan-Chieh Tseng, Narcizo M. Souza-Neto, Daniel Haskel, Martí Gich, Carlos Frontera, Anna Roig, Michel van Veenendaal, and Josep Nogués
Phys. Rev. B 79, 094404 – Published 4 March 2009

Abstract

The magnetic properties of ϵ-Fe2O3 nanoparticles are investigated by x-ray magnetic circular dichroism. Sum rules relating the orbital and spin moment in the Fe3d band to the FeL2,3 absorption cross sections show that the Fe orbital moment (morb) is considerably high, explaining the origin of the large coercivity of this material at room temperature. Moreover, at T110K, the collapse of the coercivity (Hc) and the magnetocrystalline anisotropy coincides with a strong reduction of the spin-orbit coupling evidenced by a drastic drop of morb. The decrease in morb originates from changes in the electron transfer between Fe and O ions accompanied by significant modifications of some of the Fe-O bond distances. Similarly, the recovery of morb at lower temperatures mimics the behavior of the Fe-O bond lengths.

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  • Received 13 November 2008

DOI:https://doi.org/10.1103/PhysRevB.79.094404

©2009 American Physical Society

Authors & Affiliations

Yuan-Chieh Tseng1,2, Narcizo M. Souza-Neto2, Daniel Haskel2,*, Martí Gich3,†, Carlos Frontera4, Anna Roig4,‡, Michel van Veenendaal2,5, and Josep Nogués6

  • 1Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60201, USA
  • 2Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA
  • 3Saint-Gobain Recherche, 93303 Aubervilliers, France
  • 4Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus de la UAB, 08193 Bellaterra, Catalunya, Spain
  • 5Department of Physics, Northern Illinois University, De Kalb, Illinois 60115, USA
  • 6Institució Catalana de Recerca i Estudis Avançats (ICREA) and Centre d’Investigació en Nanociència i Nanotecnologia (ICN-CSIC), Campus de la Universitat Autònoma de Barcelona, 08193 Bellaterra, Catalunya, Spain

  • *Corresponding author; haskel@aps.anl.gov
  • Corresponding author; Marti.Gich@saint-gobain.com
  • Corresponding author; roig@icmab.es

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Issue

Vol. 79, Iss. 9 — 1 March 2009

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