Magnetic Properties of Tetragonal Cobalt Manganese Ferrite Particles Prepared Using the Molten Salt Method

Both magnetization and magnetic anisotropy of CoMn x Fe 2-x O 4 particles composed of the Jahn-Teller (JT) Mn 3+ and Co 2+ ions with an expected large magnetoelastic effect were investigated. CoMn x Fe 2-x O 4 particles were prepared by using a molten salt method with KBr as a fluxing agent. A tetragonally distorted spinel structure was confirmed for x = 1.3 or higher. This suggests that an increase in Mn 3+ ions causes JT distortion of c/a > 1. However, Mn 3+ doping causes spin canting and decreased magnetization. A large saturation magnetization of M S = 44 emu/g and high coercivity of H C = 4300 Oe were observed for the sample with x = 1.4 at 10 K. In addition, the magnetic anisotropy field, H A , and H c increased with the increasing x from x = 1.3, where JT distortion was first observed.