Crystal Distortion of Submicron Sr-Ferrite Particles by Milling

Submicron-size particles of M-type Sr ferrite were obtained from fine Fe ₂ O ₃ and precipitated SrCO ₃ . The magnetic properties of the powder were σ _s =71 emu/g and H _cJ =5.5 kOe. The Hc _J of the powder was reduced to less than 40% of its initial value by dry vibration milling. SEM observations showed that the primary particle size distribution was not much different from that in the initial state. Crystal distortion was determined by X-ray diffraction studies, using the method of Warren and Averbach. The torque curve of the milled powder was measured using a highly sensitive torque magnetometer. The dependence of K ₂ /K ₁ on the measuring magnetic field was increased with milling-induced crystal distortion. The Mössbauer absorption effect was also measured. submicron particles were analyzed in comparison with coarse Sr ferrite particles (3 μm) by a conventional breaking-down process.