Investigations into the magnetic properties of rare earth compounds

Abstract

Magnetic measurements have been carried out on compounds of the form Gd(_x)Y(_1-x)Co(_2), where x varies from 1 to 0. The measurements were carried out over a wide range of temperatures and applied magnetic fields on a vibrating sample magnetometer. The results show that these compounds with high gadolinium content are strong magnetic, and their Curie points range from 400ºK inGdCo(_2) down to near zero for x 0.l. The compound YCo(_2) is shown to be antiferromagnetic, with, a Keel point of 190 K. The magnetisation versus temperature results show an anomaly im the form of a "kink" in the curves for those compounds, with x greater than 0.33, and the presence of this kink is shown to be dependent on the strength of the applied magnetic field, a minimum, or critical field Being required before the anomaly appears. The model proposed to explain, this: behaviour is. an adaptation of one proposed by Lotgering, for which an. antiferromagnetic Gd-Go coupling, an antiferromagnetic Co-Co coupling, and a ferromagnetic Cd-Cd coupling are required, Given these conditions, it is shown that a triangular configurations of moments can; exist, in which the Gd moments lie parallel to the applied magnetic field, and the cobalt moments; lie antiparallel to the applied field, but tilted alternately right and left at an angle so as to form a triangle with the Gd moment. It is shown, that such, a condition cam exist only; below a certain critical temperature, and at fields above a certain critical value. In all respects this model appears to fit the observed results well, but confirmation of the existence of such a configuration not only: in these compounds, but probably: in rare-earth - (cobalt)(_2) and rare-earth - (iron)(_2) compounds also, must await neutron diffraction measurements with a moderately high magnetic field applied to the specimens.