Temperature dependent magnetic properties of conical magnetic structure M-type hexaferrites BaFe10.2Sc1.8O19 and SrFe10.2Sc1.8O19

The magnetic properties of conical magnetic structure (CMS) hexaferrites BaFe10.2Sc1.8O19 (BFSO) and SrFe10.2Sc1.8O19 (SFSO) have been investigated under different magnetic fields and different temperatures. Results show that the single phase CMS hexaferrites BFSO and SFSO can be obtained as the sintering temperature exceeds 1473 K. Both the coercivity Hc and remanent magnetization Mr of the CMS BFSO and SFSO decrease sharply with increasing temperature below 100 K, and they become very small and almost invariant when the temperature exceeds 100 K. For both BFSO and SFSO, the field-cooling and zero-field-cooling curves differ greatly at low temperatures and resemble at high temperatures. A magnetic transition temperature Tz2 from noncollinear CMS to collinear ferrimagnetic structure is observed in both BFSO and SFSO with BFSO having higher Tz2 than that of SFSO. Moreover, the Tz2 decreases with increasing the magnetic field in both samples generally.