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Study of the phase transitions in

1999; IOP Publishing; Volume: 11; Issue: 2 Linguagem: Inglês

10.1088/0953-8984/11/2/007

1361-648X

J. Pérez-Cacho, J. Blasco, J. Garcı́a, Miguel Castro, Jolanta Stankiewicz,

Solid-state spectroscopy and crystallography

has been synthesized under high oxygen pressure from a precursor prepared by means of a sol-gel method. The material obtained is of single phase and has an orthorhombic crystal structure at room temperature. The magnetic, electrical and thermal properties have been measured over a wide temperature range. This compound exhibits a metal-insulator and a paramagnetic-antiferromagnetic transition at 400 K and at 220 K, respectively. The metal-insulator transition is of first order while the magnetic ordering is a second order transition as can be inferred from calorimetric measurements. In addition, we observe an anomaly in the resistivity near the Néel temperature indicating a change in the conduction mechanism at this temperature. Our results support local antiferromagnetic correlations above the Néel temperature for this compound.