Inducing exchange bias in La0.67Sr0.33MnO3δ/SrTiO3 thin films by strain and oxygen deficiency

D. Schumacher, A. Steffen, J. Voigt, J. Schubert, Th. Brückel, H. Ambaye, and V. Lauter
Phys. Rev. B 88, 144427 – Published 31 October 2013

Abstract

We present an exchange bias (EB) effect of variable size in La0.67Sr0.33MnO3δ single and La0.67Sr0.33MnO3δ/SrTiO3 (LSMO/STO) bilayers grown on STO substrates. Samples have been prepared by pulsed laser deposition (PLD) and high-pressure sputter deposition (HSD) in oxygen atmosphere at different oxygen pressures. Increased out-of-plane lattice parameters of the LSMO layers and reduced Curie temperatures indicate oxygen deficiencies in the samples grown at lower oxygen pressures. We found an increase of the EB and the coercive fields with decreasing oxygen pressure, whereas the growth at high pressures does not lead to an EB effect. The depth-sensitive method of polarized neutron reflectometry (PNR) reveals a region with drastically reduced, maybe even completely vanishing net magnetization in the LSMO layer at the interface to STO in the exchange-biased samples, but not in the non-exchanged-biased one. It is suggested that an antiferromagnetic structure is formed in this part of the LSMO thin film, which causes the EB effect in this system. An explanation based on the strain-doping phase diagram of LSMO is provided. Thus our findings open a route for tuning the EB effect by changing the oxygen vacancy concentrations.

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  • Received 14 December 2012

DOI:https://doi.org/10.1103/PhysRevB.88.144427

©2013 American Physical Society

Authors & Affiliations

D. Schumacher, A. Steffen, J. Voigt, J. Schubert, and Th. Brückel

  • Jülich Center for Neutron Science JCNS and Peter Grünberg Institut PGI, JARA-FIT, and Forschungszentrum Jülich GmbH, 52425 Jülich, Germany

H. Ambaye and V. Lauter

  • Spallation Neutron Source, Neutron Science Directorate, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA

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Vol. 88, Iss. 14 — 1 October 2013

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