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Observation of low, intermediate, and high spin states in GdBaCo 2 O 5.45

2002; American Physical Society; Volume: 65; Issue: 6 Linguagem: Inglês

10.1103/physrevb.65.064437

1095-3795

Sujoy Roy, Mahmud Khan, Yuqiao Guo, J. Craig, Naushad Ali,

Physics of Superconductivity and Magnetism

The magnetic and electrical transport properties and relative thermal expansion measurements on ${\mathrm{GdBaCo}}_{2}{\mathrm{O}}_{5.45}$ show the existence of a stabilized intermediate spin state of ${\mathrm{Co}}^{3+}$ in the temperature region $108 \mathrm{K}<~T<~365 \mathrm{K}.$ A charge ordering effect at 242 K due to Jahn-Teller effect followed by a ferromagnetic transition is observed in the intermediate spin state. Thermal expansion data reveal second and first order phase transitions at 163 and 359 K, respectively. These are explained as due to spin state transition accompanied by a change in the ionic radius of ${\mathrm{Co}}^{3+}$ in different spin states.