Magnetic behavior of Ni and Co doped CuMn2O4 spinels

Mn1.68Co0.24Ni0.48Cu0.6O4 was produced via slip casting and sintering of spray-pyrolysis produced powders. The magnetic properties of this composition were measured for the first time, as a function of the processing temperature (900 °C or 1000 °C sintering), in order to study the effects of Cu and Mn valence and site preference. Quantitative x-ray photoelectron spectroscopy showed that Cu+ site occupancy changed from tetrahedral to a mix of tetrahedral and octahedral with increasing sintering temperature. X-ray diffraction demonstrated that the materials had a cubic spinel structure devoid of tetragonal Jahn-Teller distortion. ac magnetic susceptibility indicated ferrimagnetic behavior below ∼109 K and spin glass behavior below ∼66 to 74 K, depending on the measurement frequency. ac susceptibility freezing temperatures were modeled with the Vogel-Fulcher law and showed intermediate characteristics, between those of canonical spin glasses and cluster glasses.

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