Dependence of the ferrimagnetic resonance linewidth on sintering conditions in manganese ferrite

Ferrimagnetic resonance linewidth of manganese ferrites, Mn1.0Fe2.0O4 has b een measured at 8.9 GHz from 77 to 320 K. Single crystal was prepared by fl oating zone technique and their composition confirmed by inductively couple d plasma spectrometry. Polycrystalline samples were sintered under differen t conditions of temperature, time, and atmosphere. Eddy current and valence exchange contributions according to Sparks' theory and a new procedure for evaluating superficial and porosity mechanisms are taken into account to a nalyze the ferrimagnetic resonance linewidth. Different contributions are p resent depending on sintering conditions: valence exchange mechanism appear s only in samples sintered under low temperatures and high pressures; condu ctivity decreases for samples sintered at high pressures; porosity is highl y raised up when sintering time decreases. Resonance fields, obtained from experimental data, are used to calculate anisotropy fields for polycrystall ine samples. (C) 1999 American Institute of Physics. [S0021-8979(99)06503-2 ].