Improvement of (BH)max in Ba-hexaferrite doped with La and Co

Abstract

In this work we produce Ba-hexaferrite nanoparticles by the ionic coordination reaction method and study the influence of La and Co ions on the magnetic properties of Ba0.7La0.3Fe12-xCoxO19 for x = (0.0, 0.25, 0.50, 0.75 and 1.0) nanoparticles. The crystalline and morphological properties were studied by X-ray diffraction and scanning electron microscopy techniques. The magnetic properties of samples were studied in a vibrating sample magnetometer under an applied field of ±6 T. The Fe occupancy in the three octahedral (12k, 2a, and 4f2), one tetrahedral (4f1) and one trigonal bipyramidal (2b) sites was studied by Mössbauer spectroscopy. The samples are single domain nanoparticles with crystallite sizes in the range 71.5-50.1 nm, decreasing with the Co doping. The results suggest that the sample with x = 0.25 had the largest (BH)max of 6.98 kJ/m3, this effect is mostly due to the occupancy of 4f2 sites by Co2+. For x > 0.25, the Co2+ occupy mainly both the 4f2 and 12k sites, the presence of oxygen vacancies is discussed.