Partial Quenching of the Magnetic Moments in Polycrystalline Co(Al x Co1-x )2O4 Samples (0 <x <0.35)

In this work, the effect of Al3+-doping in polycrystalline Co(Al (x) Co1-x )(2)O-4 samples (< x < 0.35) was studied. Samples have been synthesized via conventional state solid method. X-ray diffraction (XRD) measurements carried out at room temperature reveal that a single cubic phase has been successfully obtained for all samples. Magnetization measurements as function of temperature (2 < T < 300 K) were collected in a commercial DC superconducting quantum interference device magnetometer. The observation of an antiferromagnetic transition for all samples confirms that Co3+ ions located on octahedral sites are low spin (S = 0). On the other hand, the transition temperatures are unaffected by the Co3+-doping indicating that the empty e (g) orbitals does not play an important role in the antiferromagnetic interaction between Co2+ sited on tetrahedral sites. Besides, the evaluation of effective magnetic moment from T-dependence of magnetic susceptibility reveals that the effective moment is not totally quenched. This fact confirms both of the crystal field effects experimented by the Co ions is site-dependent and it is stronger for Co ions located in octahedral sites than tetrahedral ones.