Study of electrical transport properties of fine magnetic particles using microwave Hall effect techniques

Microwave Hall effect (MHE) techniques, combined with the resonant perturbation method, can be used to study the electrical transport properties of fine magnetic particles. In our study, an X band TE112 bimodal cylindrical cavity is built and a vector network analyzer (HP8719C) is used to conduct microwave measurements. From the change of the quality factor before and after the introduction of magnetic particles, the conductivity of the particles can be obtained. From the change in power transmission between the two orthogonal degenerate modes of the bimodal cavity before and after the application of a static magnetic field, the mobility of carriers in the particles can be obtained. The sign of the carriers can be determined by calibration or by introducing a small imbalance into the cavity. The Hall mobility of fine magnetic particles can be deduced after the saturation level of the magnetization is technically achieved. Results show that the mobility and conductivity of Fe₃O₄ fine particles are much larger than those of α-Fe₂O₃ fine particles. The sign of the charge carriers in Fe₃O₄ fine particles is found to be negative, while the charge carriers in α-Fe₂O₃ fine particles show a positive sign