Magnetic Transitions in Alloys of Gadolinium and Dysprosium

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Abstract
Magnetic properties of alloys of gadolinium and dysprosium have been studied experimentally. As the temperature is lowered, pure gadolinium makes a transition from the paramagnetic state directly to the ferromagnetic state. Pure dysprosium transforms under somewhat similar circumstances from the randomly oriented spin structure to an ordered spin state, commonly referred to as a spiral structure. As the temperature is lowered further, this nonferromagnetic spiral structure changes to the parallel aligned spin structure, which is ferromagnetic. The transition temperatures have been investigated as a function of composition of the alloys and also as a function of the ambient pressure. The strength of the internal magnetic interaction evidently depends strongly on interatomic spacings, which are pressure-dependent. The present experiments show that the binary alloys transform directly from the paramagnetic state to the ferromagnetic state when they contain less than 50∼ dysprosium. The dysprosium-rich alloys evidently pass through the oscillatory spin state before they become ferromagnetic. Results at atmospheric pressure are consistent with previously reported experiments by others. As the ambient pressure is increased, significant changes occur in the temperatures at which the magnetic transitions occur. In most of the cases, both the Néel temperature (random to spiral structure) and the Curie temperature (parallel aligned structure) decrease with increasing pressure. However, in some cases the Curie temperature appears to increase with increasing pressure. The results are discussed in terms of the Ruderman-Kittel-Kasuya-Yosida model.