Micromagnetic simulation on domain structure of Strontium Hexaferrite (SrFe₁₂O₁₉)

Strontium Hexaferrite (SrFe₁₂O₁₉) is the M-type hexaferrites with a hexagonal crystal structure. It is a hard magnetic material with the magnetic properties intrinsically linked to its crystalline structure. It is used in various applications viz. permanent magnets, microwave devices, disk drivers, etc. Understanding the magnetization dynamics of SrFe₁₂O₁₉ (SFO) and its magnetic domain structures as a function of size are vital for practical applications for permanent magnet. In present study, the domain structures of SFO have been investigated systematically by means of a micromagnetic simulation for various morphologies and dimensions. The domain structures appear as a result of the competition between Demagnetization and Exchange energy, where the Demagnetization energy depends on the morphology and decides the transition region from single- to multi-domain state. At 120 nm, the sample is in a single domain state (blue color) whereas at 260 nm the sample shows multi domain behaviour (2 blue domains and 1 red domain with opposite magnetization). In the multi-domain state, the domain wall (Bloch wall type) width also varies as a function of size and morphology, which arises due to the competition of anisotropy and exchange energies