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Grain boundary effects in bulk colossal magnetoresistive (CMR) manganites and manganite/insulator composites: electrical and magnetic properties♣

P. VANDERBEMDEN1,* , B. VERTRUYEN1, M. AUSLOOS1, B. RIVAS-MURIAS1, V. LOVCHINOV2

Affiliation

  1. University of Liège, SUPRATECS research group, Departments of Electrical engineering & Computer science (B28), Chemistry (B6) and Physics (B5), Sart-Tilman, B-4000 Liège, Belgium
  2. Institute of Solid State Physics, Bulgarian Academy of Sciences, 72 Tzarigradsko Chaussee Blvd., 1784 Sofia, Bulgaria

Abstract

In the first part of this paper, we discuss the effects of grain boundaries on the properties of bulk colossal magnetoresistive (CMR) manganites. We compare the electrical resistivity and AC magnetic susceptibility of perovskite La-Ca-Mn-O samples with the same nominal stoichiometry but differing in their microstructure: (i) a single grain sample, (ii) a sample containing two grains and (iii) a polycrystalline sample. Emphasis is placed on information that can be deduced from the measurements in each case. In the second part of the paper, we report the data measured on composite samples containing a CMR phase (La-Ca-Mn-O) and an insulating phase (Mn 3O 4 ). The results are discussed in the framework of percolation theory. We show how the grain boundaries affect the electrical properties of these materials, and we highlight the crucial role of geometric (demagnetization) effects on the resistance vs. magnetic field measurements..

Keywords

Colossal Magnetoresistance, Electrical properties, Magnetic properties, Grain boundaries.

Submitted at: Nov. 5, 2008
Accepted at: Sept. 9, 2009

Citation

P. VANDERBEMDEN, B. VERTRUYEN, M. AUSLOOS, B. RIVAS-MURIAS, V. LOVCHINOV, Grain boundary effects in bulk colossal magnetoresistive (CMR) manganites and manganite/insulator composites: electrical and magnetic properties♣, Journal of Optoelectronics and Advanced Materials Vol. 11, Iss. 9, pp. 1115-1121 (2009)