EPR Pressure Experiments on Rare Earths in Diamagnetic Garnets and the Single-Ion Magnetostriction of Rare-Earth Iron Garnets

The EPR spectra of Gd3+, Yb3+, and Er3+ in diamagnetic garnet hosts have been measured as uniaxial pressures were applied to the crystal, and the parameters ∂gkl/∂εij and ∂Dkl/∂εij evaluated. A theory connecting these parameters with the magnetoelastic energy of the rare-earth iron garnets has been developed, and the single-ion contribution to the magnetostriction constants λ100 and λ111 of GdIG, YbIG, and ErIG calculated. In most cases the predicted single-ion magnetostriction constants are of the same sign and within a factor of 2 of the observed magnetostriction constants at low temperatures. We conclude that single-ion effects play a dominant role in the magnetoelastic behavior of the rare-earth iron garnets.