Magnetostriction of Dysprosium, Holmium, and Erbium Iron Garnets

Abstract

The temperature and field dependences of the anisotropic magnetostriction coefficients of Dy, Ho, and Er iron garnets were measured from 78°K to room temperature. At the compensation points there is a reversal in the field-dependent magnetostriction (anisotropic forced magnetostriction) and a sharp dip in the apparent saturation magnetostriction. At high temperatures, the magnetostriction coefficients approach the values measured previously for YIG (≅10−6). At low temperatures, large strains arise because of the large magnetoelastic coupling of the rare-earth ion: λ100 (0°K) REIG/λ100 (0°K) YIG≅103; λ111 (0°K) REIG/λ111 (0°K) YIG≅50. Estimates of the 0°K magnetostrictions based upon the single-ion theory of magnetoelastic coupling are −1400, −930, and 420×10−6 for λ100, and −550, −220, and −300×10−6 for λ111 of Dy, Ho, and Er iron garnets, respectively. These values, although 50 to 1000 times larger than YIG, are one order of magnitude smaller than the enormous strains observed in the heavy rare-earth metals. This difference can be accounted for by the difference in elastic moduli and density of rare-earth ions. In both the metal and garnet the magnetoelastic coupling coefficient of the rare-earth ion is approximately 103 cm−1.