Abstract
Internal friction of ferromagnetic substance cooled in longitudinal magnetic field is studied both theoretically and experimentally. Two theories are developed on the basis of two different ideas on the elementary magnetizing process. The first theory which assumes that the substance is magnetized by the displacement of 180°-domain boundary leads to the conclusion that internal friction at the demagnetized state must vanish by field-cooling. The second theory assuming that the substance is magnetized by the reversible and irrevarsible rotation of spontaneous magnetization concludes that internal friction at the demangnetized state must increase appreciably by field-cooling in contrast to the former case. On the other hand, experimental investigation of both field-cooled and commonly annealed substances is carried out for Ni3Fe. Comparing the experimental and two different theoretical results, the latter theory is known to be more convenient to explain the measured data than the former theory. The magnetic domain structure of field-cooled substance is so concluded from this investigation that the spontaneous magnetization in the substance is fixed to the direction closer to the applied magnetic field than in usually treated substance, and that the magnetizing process is still rotation of spontaneous magnetization from the newly fixed direction.
