Magnetic and crystal-field properties of dysprosium dihydrides and trihydrides fromDy161Mössbauer studies

Abstract

The saturation hyperfine magnetic field at the ${}_{}{}^{161}{}_{}{}^{}\mathrm{Dy}$ nucleus measured with the 26 keV Mössbauer resonance in Dy${\mathrm{H}}_{2.00}$ identifies a ${\Gamma }_7$ crystal-field ground state for the ${\mathrm{Dy}}^{3+}$ atom. This state originates from a cubal surrounding of the ${\mathrm{Dy}}^{3+}$ atom by ${\mathrm{H}}^{-}$ atoms, in agreement with the hydridic model for rare-earth hydrides. An analysis of the hyperfine parameters and of the Schottky anomaly permits one to obtain the crystal-field parameters $W=0.83\mathrm{}\pm 0.03$ K and $x=0.24\mathrm{}\pm 0.02$, and the exchange field ${\mathrm{H}}_{\mathrm{ex}}=26\mathrm{}\pm 5$ kOe. Dy${\mathrm{H}}_2$ exhibits a long-range magnetic order at 3.3 K while between 3.3 and 6 K fairly complex short-range order is observed. A possible explanation for this behavior is provided. Dy${\mathrm{H}}_3$ remains paramagnetic down to 1.6 K.