The effects of doping ferromagnetic spinel CdCr2Se4 with Sb3+ ions

Semiconducting spinel CdCr2Se4 orders ferromagnetically below TC=130 K. A series of single-crystals of CdCr2Se4 doped with Sb3+ ions has been synthesized in order to study an effect of the substitution on the cation distribution and the magnetic properties. The compounds of CdySbxCrzSe4 have been investigated by means of X-ray diffraction, magnetization measurements and electron spin resonance spectroscopy. Two selected samples of the composition (Cd1−xSbx)[Cr2]Se4 with x  =0.13 and 0.44 retained cubic symmetry with space group Fd3¯m. The unit cell parameter appeared to be sensitive to the concentration of Sb3+ admixture: it increases with x, despite a close similarity in the ionic radii of Cd2+ and Sb3+ in tetrahedral coordination. Upon partial substitution of Cd2+ by Sb3 no obvious change in the Curie temperature was observed, however, the effective magnetic moment slightly increased, what may result from the appearance of Cr2+ ions. The characteristic feature of the system studied is an extended range of short-range magnetic order, in which the magnetic properties in the paramagnetic state are governed by the formation of ferromagnetic clusters, as indicated by both the bulk magnetometric and spectroscopic data.

Temperature dependent evolution of the ESR spectrum for the (Cd0.56Sb0.44)[Cr2]Se4 single-crystal showing inhomogeneous nature of the ferromagnetic ordered state below Tc=130 K. At temperature 127 K a fraction of the paramagnetic phase can still be observed.Figure optionsDownload as PowerPoint slide