Magnetocrystalline interactions in MnCr2O4 spinel
E. WINKLER; S. CANOSA BLANCO; M.A. LÓPEZ QUINQUELA; J. RIVAS; A. CANEIRO; M.T. CAUSA; M. TOVAR
PHYSICAL REVIEW B
AMER PHYSICAL SOC
Año: 2009 vol. 80 p. 1044181 - 1044188
In this work we present a magnetic, structural, and electron spin resonance ESR study of the geometricallyfrustrated MnCr2O4 spinel in an extended range of T 21000 K. At the lowest temperature T18 Kthe ESR lineshape is compatible with the coexistence of spiral and ferrimagnetic spin ordering. Above TC41 K, magnetic susceptibility and ESR intensity coincide with each other showing the typical behaviorof a ferrimagnet. From the T vs T dependence, absolute values for the three exchange constants JMnCr, JCrCr,and JMnMn were determined. Our results indicate that i these values are approximately independent of T, iithe antiferromagnetic direct Cr-Cr exchange is the main interaction, and iii JMnMn is indeed not negligible ascompared with JMnCr and JCrCr. One noticeable anomaly in the temperature dependence of the ESR linewidthis observed at T450 K. This behavior is accounted by a 30% variation in the extrapolated high-temperaturelinewidth and it is attributed to a crystalline distortion not reported previously. Experiments of hightemperaturex-ray diffraction allowed us to associate this distortion to a deformation of the oxygen sublattice.ESR and x-ray results are both compatible with a more symmetric high-temperature structure.