Structural and magnetic properties of Zn x Mn 3-x O 4 spinels
Résumé
To study structural and magnetic properties of spinels a series of ceramic samples with a different ZnMn ratio was prepared by high-temperature annealing in air followed by quenching in liquid nitrogen. The spinels with nominal composition of Zn x Mn 3-x O 4 (x=0-1.29) were characterized by means of X-ray diffraction, Raman spectroscopy, scanning electron microscopy and SQUID magnetometry. Two tetragonal spinels of the same I4 1 /amd space-group were identified based on the crystallographic, vibrational and grain-morphology point of view and described in detail. The unit-cell parameters and phase ratio of the spinel phases were determined using Rietveld refinement. According to the factor-group analysis the majority of the vibrational modes were identified in the Raman spectra. The magnetic properties of Zn x Mn 3-x O 4 spinels are in agreement with a model of nanoscale ferrimagnetic Mn 3 O 4 clusters in the antiferromagnetic ZnMn 2 O 4 matrix (T N ≈60 K). New features are a constricted hysteresis loop for x=0.3, and the effect of defects on magnetic properties for high Zn content which points to a good quality of the samples prepared by a solid state reaction. © 2016 Elsevier B.V. All rights reserved.