Mossbauer and magnetic properties of Co-Ti substituted barium hexaferrite nanoparticles

Co-Ti substituted M-type hexagonal barium ferrite nanoparticles BaFe12-2xCoxTixO19 (0less than or equal toxless than or equal to1.0) have been prepared by a sol-gel method. Magnetic and structural properties of the powders were characterized with a Mossbauer spectroscopy, vibrating sample magnetometer, x-ray diffraction (XRD), thermogravimetry (TG), and differential thermal analysis (DTA). The decomposition of amorphous hydroxides in the dried precipitate continued until 570 degreesC, according to a TG-DTA analysis. The result of XRD measurements shows that the a and c lattice parameters increase with increasing x from a=5.882 and c=23.215 Angstrom for x=0.0, to a=5.895 and c=23.295 Angstrom for x=1.0. The Fe-57 Mossbauer spectra were fitted by a least-squares technique with four subpatterns of Fe sites in the structure and corresponding to the 4f(2), 4f(1)+2a, 12k, and 2b sites. The relative spectra areas of BaFe10CoTiO19 at 295 K were 15%, 30%, 50%, and 5% for 4f(2), 4f(1)+2a, 12k, and 2b subspectra, respectively. The 2b site had a very large quadrupole splitting. The isomer shifts indicated that the valence states of the Fe ions were ferric. The magnetization slightly decreases and the coercivity, H-C, drops dramatically from about 5014 to 228 Oe as x increases from 0.0 to 1.0. Co-Ti substituted barium hexaferrite to be controlled to reduce their coercivities with a small decrease of their magnetization. (C) 2002 American Institute of Physics.