Magnetic Study of the Heavier Rare-Earth Iron Garnets

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Abstract
Magnetic measurements, over the temperature range 1.4-298°K, have been made on ultrapure crystals of the heavier rare-earth (Gd to Yb) iron garnets, allowed to rotate freely in the magnetic field. Measurements in the same temperature range have also been made on polycrystalline Lu iron garnet. At tempera-peratures near 1.4°K, the iron garnets of Gd, Tb, Dy, and Ho are apparently magnetically saturated at moderate fields, while those of Er, Tm, and Yb are not saturated at such fields, nor at 4.2°K to a field of ≈ 80 kOe. The polycrystalline Lu iron garnet appears to be magnetically saturated over the whole temperature range investigated at a field ≤9.9 kOe. In all cases in which saturation was not attained, the behavior of the moment versus field was linear, and spontaneous magnetizations were obtained by extrapolation of moment versus field to zero field. Except for the Er and Yb iron garnets, all 0°K spontaneous magnetizations found in this study are higher than those reported by Pauthenet. For Er iron garnet, a lower value is obtained, possibly because of extrapolation of moment versus field to zero instead of infinite field. Tm iron garnet does not have a compensation point and Yb iron garnet appears to be compensated from 0 to ∼6°K.