Magnetic Alignment at Reduced Field Intensity Due to Decrease of Temperature Observed for Nonferromagnetic Particles Possessing Paramagnetic and Diamagnetic Anisotropy

摘要

The reduction of field intensity to achieve magnetic alignment of micron-sized nonferromagnetic particles caused by the variations of various parameters was studied systematically, based on the experimental data obtained for various non ferromagnetic materials. The field intensity where the order parameter reached = 0.8, denoted by B_s, was proportional to the square root of temeprature for graphite crystals free of paramagnetic ions. The relationship was consistent with the Langevin theory on magnetic alignment. The majority of inorganic oxides is expected to possess diamagnetic anisotropy, since their origin can be explained quantitatively by assuming a constant anisotropy on the individual bonding orbital composing the material. B_s is expected to decrease with the temperature for these oxides, in the same manner observed for the graphite grains. Experiments on talc and kaolinite particles including paramagnetic ions revealed that B_s was proportional to temperature when the paramagnetic concentration was high, since the paramagnetic anisotropy followed the Curie law.