Evolution of the magnetic and magnetotransport properties of the Ga-substituted manganite compounds La2xSrxMnGaO6

A. I. Coldea, S. J. Blundell, I. M. Marshall, C. A. Steer, J. Singleton, F. L. Pratt, L. D. Noailles, M. J. Rosseinsky, L. E. Spring, and P. D. Battle
Phys. Rev. B 65, 054402 – Published 27 December 2001
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Abstract

We report a series of magnetic and magnetotransport studies performed on Ga-substituted manganite compounds La2xSrxMnGaO6(x<~0.7). We replace half of the Mn ions in LaMnO3 with diamagnetic ions Ga3+ and find that the system transforms into a ferromagnet as the result of local coherent and incoherent distortions. Following additional doping with Sr ions we find that the La2xSrxMnGaO6 compounds remain ferromagnetic up to x0.3 but for higher concentrations the competition between the ferromagnetic and antiferromagnetic superexchange interactions, together with the randomness in distribution of the magnetic ions, lead to magnetic frustration, cluster-glass and spin-glass behavior. All compounds are insulating and the activation energy decreases almost linearly with x. μSR measurements suggest the existence of short-range magnetic correlations in the high-temperature region. We measure a significant increase in the muon-spin relaxation rate at low temperatures due to fluctuations of random internal magnetic fields. The observed magnetoresistance in the high-temperature region is mainly a consequence of the reduction of the spin disorder on a local scale, and is as high as 50% in 14 T and T>100K for samples with x=0.3 and x=0.5.

  • Received 11 July 2001

DOI:https://doi.org/10.1103/PhysRevB.65.054402

©2001 American Physical Society

Authors & Affiliations

A. I. Coldea, S. J. Blundell, I. M. Marshall, C. A. Steer, and J. Singleton

  • Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom

F. L. Pratt

  • ISIS Muon Facility, Rutherford Appleton Laboratory, Chilton, Oxfordshire OX11 0QX, United Kingdom

L. D. Noailles and M. J. Rosseinsky

  • Department of Chemistry, University of Liverpool, Liverpool L69 7ZD, United Kingdom

L. E. Spring and P. D. Battle

  • Inorganic Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QR, United Kingdom

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Vol. 65, Iss. 5 — 1 February 2002

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