Magnetic phase transitions in substituted barium ferrites BaFe12-x(Ti0.5Co0.5)xO19 (x=0-5)

High temperature magnetic properties for a series of Ti, Co-substituted M-type barium hexaferrite BaFe12-x(Ti0.5Co0.5)(x)O-19 (x=0-5) have been studied by measuring magnetization and magnetic susceptibility. BaFe12O19 (x=0) shows the hard magnetic property at room temperature in magnetization curve. The saturation magnetization M-s and the coersivity H-C decrease with increasing Ti, Co composition x. Curie temperature T-C shifts to lower temperature with x and becomes T-C = 491 K in the composition x=2.5. At this composition, another ferrimagnetic state was observed above T-C; the ferrimagnetic to paramagnetic transition temperature locates at T-C2=752 K. The second transition temperature T-C2 has a maximum at around x=3 and becomes 703 K at x=5 where the low transition temperature locates at T-C=219 K. In the high temperature ferrimagnetic phase, magnetization value is small compared to the low ferrimagnetic phase. Thus a canted or uncompensated antiferromagnetic structure produced by the Fe-Co and/or Co-Co exchange interaction can be considered. (C) 2012 Elsevier B.V. All rights reserved.