Magnetic properties of nanodispersed ferrite powders with cryochemical prehistory

Calcium hexagonal ferrite in the form of a system of nanocrystals has been synthesizes using elements of cryochemical technology for the first time. The obtained ensemble of particles corresponds to the model Stoner-Wohlfarth system according to the following characteristics: the phase composition, the shape of the basic magnetization curve, and the coercive force. The temperature dependences of the magnetization in the range 300–700 K at fixed values of the magnetic field indicate the presence of a transition to the super-paramagnetic (SPM) state. The boundary temperatures TBH(1) and TBH2 of the range of the SPM transition have been determined, and the role of the external magnetic field, which stimulates the transition in this process in accordance with the theory, has been confirmed.