Efficiency of magnetic alignment found in various paramagnetic and diamagnetic solids detected by simple rotational oscillation of sample in microgravity

Abstract

Oscillation of magnetically stable-axis with respect to a static field below 20 kOe occurred for various solids without spontaneous magnetic moment. The oscillation was caused by anisotropy of magnetic susceptibility Δχ. According to theoretical consideration on the origin of diamagnetic and paramagnetic anisotropy, Δχ values of ordinary solid is expected to range over 6 orders of magnitude. These Δχ values can be obtained from period of the above-mentioned oscillation; small Δχ values were detectable because effect of restoration torque of a fiber that suspended the sample was excluded in the measurement. Δχ above 1 × 10-9 emu/g were detected at terrestrial gravity in a field below B = 20 kOe. The fiber itself was excluded by floating a sample in microgravity, for the purpose of detecting Δχ below 1 × 10-9 emu/g. Alignment of micron-sized crystals dispersed in fluid at room temperature is achieved below 2 Tesla for most of the solids since their Δχ value is above 1 × 10-9 emu/g. Efficiency of magnetic alignment is enhanced considerably for ordinary oxide when resultant Δχ is increased by paramagnetic impurity ions up to level of 10-5 emu/g. © 2007 The Japan Institute of Metals.