MAGNETIC ORDERING TEMPERATURES OF SINGLE CRYSTALS OF RARE EARTH METALS AT HIGH PRESSURES - GADOLINIUM-TERBIUM-DYSPROSIUM

The magnetic ordering temperatures of single crystals of gadolinium, terbium and dysprosium have been determined experimentally at hydrostatic pressures up to 6 kbar. The Curie temperature of gadolinium decreases with pressure at the rate of (- 1·40 ± 0·02) × 10-3 °K. bar-1. At high temperatures terbium and dysprosium undergo an antiferromagnetic-paramagnetic transition at the Néel temperature θn, and at lower temperatures a ferromagnetic-antifeiromagnetic transition at the Curie temperature θc. For terbium dθn dp = (- 0·84 ±0·02) × 10-3 °K. bar-1 and dθc dp = (- 1·24 ± 0·02) × 10-3°K. bar-1; for dysprosium dθN dp = (- 0·41 ± 0·01) × 10-3°K. bar-1 and dθc dp = (- 17midot;27 ± 0·02 × 10-3 °K. bar-1. These variations result from the modifications of the exchange and anisotropy energies with the interatomic distances. At atmospheric pressure they contribute to the variations of the crystallographic parameters and the magnetic structures with temperature. Yet, they are not sufficient to interpret them completely. © 1968.