Magnetic Structure Properties of Gd–Y and Gd–Sc Alloys

Abstract

The magnetic structure properties of several specimens in the gadolinium-scandium and gadolinium-yttrium alloy systems have been determined by neutron diffraction using the low-absorbing isotope 160Gd. Neutron patterns were taken from annealed powder samples at temperatures from 4° to 300°K. In both systems, the alloys show ferromagnetism at high gadolinium concentrations and antiferromagnetism at low concentrations. The concentration at which this change from ferro- to antiferromagnetism occurs is about 80 at.% for Gd–Y and about 70 at.% for Gd–Sc. The observed antiferromagnetic structures are spiral type with turn angles between the moments in adjacent layers which approach 50 deg. per layer at low Gd concentrations. The ordering temperatures decrease with decreasing Gd concentration more rapidly in the Sc than in the Y alloys. Thus these alloys behave similarly to the other rare earth Y and Sc alloys studied previously. Dilution of Gd by Y and Sc affects the anisotropy of gadolinium differently. An 80 at.% Gd in Sc alloy has a temperature variation of the angle the ferromagnetic moment makes with the c axis similar to pure Gd in which this angle is 0° at Tc, increases to 65° as the temperature is lowered, and then returns to about 32° at very low temperatures. An 80 at.% Gd in Y alloy, on the other hand, has its ferromagnetic moment about 70° from the c axis at all temperatures below Tc. In both systems, the antiferromagnetic spiral structure has the moments in the base plane perpendicular to the c axis.