Influence of oxygen vacancies on the magnetic properties of ZnFe2O4 bulk powders

K.L. SALCEDO RODRÍGUEZ; J.J. MELO QUINTERO; G. PASQUEVICH; P. MENDOZA ZÉLIS; L. A. ERRICO; S.J. STEWART; CLAUDIA E. RODRÍGUEZ TORRES

Berlin, Alemania

Congreso; 79th Annual Meeting of the DPG and DPG Spring Meeting; 2015

To investigate the influence of oxygen vacancies in the ferromagnetism observed in Zn-ferrites systems[1] we have performed an experimental study on bulk ZnFe2 O4 powders submitted subjected to thermal treatments up to 873 K under low oxygen pressure atmosphere. The effect of vacancies on the structural and magnetic properties of ZnFe2 O4 have also been studied by DFT-based ab initio calculations. The x-ray diffraction patterns indicate that all samples consist of single-phase ferrite The results of magnetic measurements show the coexistence of ferromagnetic- like and paramagnetic components. Further, both the saturation magnetization and paramagnetic susceptibility progressively decrease as the ferrite is annealed up to 673K. For higher annealing temperatures both magnitudes increase reaching the maximum values at 873 K. Mossbauer spectroscopy measurements performed at room temperature show a unique doublet for all samples. Changes on the hyperfine parameters values are only detected for samples annealed at temperatures higher than 673K. Theoretical calculations using the full potential augmented plane waves plus local orbitals method (FP-APW+lo) were performed also, considering different approximations of exchange correlation potential (GGA, GGA +U)considering the normal, inverted and oxygen-deficient ferrites. The comparison between the experimental and calculated hyperfine parameters indicated the possibility of a reversal process of inversion to lower temperatures (603 K to 653 K, approx.) and vacancies formation process at the higher temperatures (683 K to 873 K) is occurring.[1] C. E. Rodríguez Torres et al, Physical Review B 89, 104411 (2014)[1] C. E. Rodríguez Torres et al, Physical Review B 89, 104411 (2014)