Effect of uniaxial stress on the helimagnetic-ferromagnetic phase transition in single-crystal dysprosium
Benningfield, L. V.
Donoho, Paul L.
Master of Arts
The effect of an applied uniaxial stress on the value of the critical field, at which the helimagnetic-ferromagnetic phase transition occurs, in single-crystal dysprosium has been studied. Measurements were made with stress applied along the hexagonal axis, at temperatures between 85 K and 179 K, and the maximum stress employed was 6 bar. This is comparable to the effective internal stress due to magnetostriction naturally occurring in dysprosium. At all temperatures in the range studied, the critical field increased linearly with increasing stress; the maximum shift in the critical field was approximately 1.5 kOe. This increase in the critical field can be attributed qualitatively to the fact that the application of compressive stress opposes the normal magnetostrictive expansion of the hexagonal axis which accompanies the phase transition. As a result, a larger magnetic field is required in order to overcome the tendency toward helical ordering due to the nature of the exchange energy. A comparison of the experimental results with theoretical predictions based on the usual phenomenological Hamiltonian permits a more accurate determination of the magnetoelastic contributions to this Hamiltonian than has been previously reported.