Study of the magnetic state of a highly dispersed BaO · 6Fe2O3 system with near-critical particle size

An investigation was made of the magnetic state of a system of highly anisotropic BaO · 6Fe₂O₃ nanocrystals several lattice parameters thick and having a near-critical volume (∼10⁻¹⁸ cm³), obtained using cryochemical technology. It is observed that the particles are transformed to the superparamagnetic state and it is shown that the external magnetic field plays a role in its formation. An H-T diagram was obtained for the temperature range 300 K-T _c, which shows various regions uncharacteristic of the macro-object, which are specifically attributed to the distribution over the anisotropy fields in the system and the impaired magnetic structure in the surface zone of the particles. Relatively large regions of magnetic fields and temperatures were observed where reversible rotation of the magnetization vector of particles with near-critical volume plays an important role. Fiz. Tverd. Tela (St. Petersburg) 40, 1294–1297 (July 1998)