Research and Development to Investigate the Microstructure of the Internal Magnetic Field in Ferro-, Ferri-, and Antiferromagnetic Solids

摘要

Single crystals of gadolinium metal were studied by the separate techniques of high field magnetization and ferromag netic resonance. The former showed the adequacy of a molecular field model description while the latter uncovered a significant change in g-factor at the ordering temperature. The consequences of the presence of a biquadratic exchange term in addition to the usual bilinear one and of the formally related exchange-striction were examined. Attention was focused upon modifications to molecular field model predictions and functional relations were found for hitherto-unexplained magnetic behaviors that occur very widely in nature. Research into the antiferromagnetism of a number of layer-like compounds was undertaken with the general goal of evaluating exchange interactions from their behavior in high magnetic fields. Apart from the explorations of metamagnetic behavior, two new phenomena were observed: the presence of Van Vleck type paramagnetic susceptibility in fields higher than those required for 'ordinary' saturation of the antiferromagnetic system, and a nonlinear (concave upwards) low-temperature transverse magnetization curve below saturation. (Author)