Interfacial Ferromagnetism and Exchange Bias in CaRuO3/CaMnO3 Superlattices

C. He, A. J. Grutter, M. Gu, N. D. Browning, Y. Takamura, B. J. Kirby, J. A. Borchers, J. W. Kim, M. R. Fitzsimmons, X. Zhai, V. V. Mehta, F. J. Wong, and Y. Suzuki
Phys. Rev. Lett. 109, 197202 – Published 7 November 2012

Abstract

We have found ferromagnetism in epitaxially grown superlattices of CaRuO3/CaMnO3 that arises in one unit cell at the interface. Scanning transmission electron microscopy and electron energy loss spectroscopy indicate that the difference in magnitude of the Mn valence states between the center of the CaMnO3 layer and the interface region is consistent with double exchange interaction among the Mn ions at the interface. Polarized neutron reflectivity and the CaMnO3 thickness dependence of the exchange bias field together indicate that the interfacial ferromagnetism is only limited to one unit cell of CaMnO3 at each interface. The interfacial moment alternates between the 1μB/interface Mn ion for even CaMnO3 layers and the 0.5μB/interface Mn ion for odd CaMnO3 layers. This modulation, combined with the exchange bias, suggests the presence of a modulating interlayer coupling between neighboring ferromagnetic interfaces via the antiferromagnetic CaMnO3 layers.

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  • Received 17 April 2012

DOI:https://doi.org/10.1103/PhysRevLett.109.197202

© 2012 American Physical Society

Authors & Affiliations

C. He1,*, A. J. Grutter1,2, M. Gu3, N. D. Browning3,†, Y. Takamura3, B. J. Kirby4, J. A. Borchers4, J. W. Kim5, M. R. Fitzsimmons5, X. Zhai1,‡, V. V. Mehta1,2, F. J. Wong1, and Y. Suzuki1,2,6

  • 1Department of Materials Science and Engineering, University of California, Berkeley, California 94720, USA
  • 2Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
  • 3Department of Chemical Engineering and Materials Science, University of California, Davis, California 95616, USA
  • 4NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
  • 5Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
  • 6Department of Applied Physics and Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California 94305, USA

  • *chunyong.he@gmail.com
  • Present address: Fundamental and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, WA 99352, USA.
  • Present address: Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology, China.

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Issue

Vol. 109, Iss. 19 — 9 November 2012

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