Intrinsic anomalous magnetic anisotropy of CdCr2S4

The magnetocrystalline anisotropy of the ferromagnetic spinel CdCr2S4 was investigated by ferromagnetic resonance measurements. By avoiding any contact to iron during the sample preparation we can exclude that the anisotropy is due to ferrous impurities, and by performing wavelength dispersive electron probe microanalysis as well as annealing experiments, it is demonstrated that the samples possess almost ideal stoichiometry. The resonance data suggest that compositional deviations from the stoichiometry up to 10(-3) have no influence on our conclusion that the magnetocrystalline anisotropy is an intrinsic property of CdCr2S4, caused by trigonal distortion of the sulfur octahedra surrounding the Cr3+ ions. Anomalous low-temperature linewidth maxima in the < 111 > directions can be understood by considering the crystal fields acting on inequivalent sites of the magnetic ions in the spinel structure and by taking into account the effect of exchange narrowing.