Magnetic moment of Fe3O4 films with thicknesses near the unit-cell size

G. F. M. Gomes, T. E. P. Bueno, D. E. Parreiras, G. J. P. Abreu, A. de Siervo, J. C. Cezar, H.-D. Pfannes, and R. Paniago
Phys. Rev. B 90, 134422 – Published 28 October 2014

Abstract

We perform a systematic study on the evolution of the magnetic spin moment (ms) of epitaxial [100]- and [111]-magnetite films of increasing thickness. The ultrathin films are characterized by low-energy electron diffraction, x-ray absorption spectroscopy, and x-ray magnetic circular dichroism (XMCD). By employing sum rules on the XMCD spectra we obtain ms=3.6 μB/f.u. for samples of around 35 Å. This is considered a bulk value and has been reported only for films more than 10 times thicker. Moreover, we show that even 10-Å-thick magnetite already presents a significant magnetic moment. For both grown directions the moment increases similarly with the thickness. The ferromagnetic behavior for each iron ion site (Feocta2+, Feocta3+, Fetetra3+) of Fe3O4 is measured by monitoring XMCD peaks. The deduced hysteresis curves (per ion, per site) exhibit a coercive field of 300 Oe. Our results show that both the ferrimagnetic order and the bulk moment value are preserved at room temperature around the thickness of 2 unit cells.

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  • Received 9 July 2014
  • Revised 2 October 2014

DOI:https://doi.org/10.1103/PhysRevB.90.134422

©2014 American Physical Society

Authors & Affiliations

G. F. M. Gomes1,*, T. E. P. Bueno1, D. E. Parreiras1, G. J. P. Abreu2, A. de Siervo2, J. C. Cezar3, H.-D. Pfannes1, and R. Paniago1

  • 1Departamento de Física, ICEx, Universidade Federal de Minas Gerais, 31270-901 Belo Horizonte, MG, Brazil
  • 2Instituto de Física Gleb Wataghin, Universidade Estadual de Campinas, 13083-859 Campinas, SP, Brazil
  • 3Laboratório Nacional de Luz Síncrotron, C.P. 6192, 13083-970 Campinas, SP, Brazil

  • *gustavofmg@gmail.com

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Vol. 90, Iss. 13 — 1 October 2014

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