Content area
Full Text
J Mater Sci: Mater Electron (2013) 24:916926 DOI 10.1007/s10854-012-0850-2
Effect of divalent cation substitution in the magnetoplumbite structured BaFe12O19 system
Venugopalan Anbarasu P. M. Md Gazzali
Thangavelu Karthik Appasamy Manigandan
Kandasamy Sivakumar
Received: 21 June 2012 / Accepted: 23 July 2012 / Published online: 10 August 2012 Springer Science+Business Media, LLC 2012
Abstract Synthesis of magnetically ordered barium hexaferrite powders and the adjustment of magnetic properties for perpendicular magnetic recording media are realized through substitution of divalent cation (Ca) in the BaFe12O19 system. The Ca2? substituted Ba1-xCaxFe12O19 (where x = 0.05, 0.1, 0.15 and 0.2) compounds have been prepared through solid state reaction technique. The powder X-ray diffraction analysis reveals that all the prepared compounds crystallized in magnetoplumbite hexagonal structure and the at hexagonal platelet morphology of the crystallites was identied through scanning electron microscopy. The formation of magnetoplumbite structured Ba1-xCaxFe12O19 system due to mechanical activation was supported by micro-Raman measurements. Both pure and
Ca substituted BaFe12O19 compounds exhibit sharp intense peaks which reveals defect free environment in the crystal lattice. From the room temperature magnetization studies,
it was observed that the saturation magnetization (MS) and
remanent magnetization (MR) values drastically decreases for the Ba0.95Ca0.05Fe12O19 compound which may be due
to the existence of spin canting effect and leads to the reduction of super exchange elds. The increase in MS and
MR values for the Ba0.9Ca0.1Fe12O19 and Ba0.85Ca0.15-
Fe12O19 compounds could be attributed to the enhanced hyperne elds at 12k and 2b sites due to the strengthening of Fe3?OFe3? super exchange interactions. A large reduction in the coercivity value from 3,090 to 1,548 Gauss may be attributed to the fall in magneto crystalline anisotropy. The high temperature magnetization studies infer that while increasing substitution level of Ca in the BaFe12O19 system results in decreasing trend in Curie temperature. The room temperature dielectric measurement shows that the incorporation of Ca2? in the BaFe12O19 system results with increase in the dielectric constant and this case substantiates the space charge polarization. The magnetically ordered BaFe particulate having higher saturation and low coercivity values with superior magnetic and dielectric behaviour exhibiting the possibility for future high-recording-density storage products.
1 Introduction
Magnetic ceramics have found commercial applications ever since 1940s. A wide range of substitutional solid solubility makes it possible...