The low temperature contributions to β-uranium hydride specific heat

Abstract

Recent observation of Proton Magnetic Resonance in ferromagnetic β-uranium hydride by Barash et al. led us to perform a new analysis of the specific heat data of Flotow and Obsborne for this compound. In the temperature region 1.469 K⩽ T⩽3.927 K, the specific heat C was found to be given by the expression C=29.504 T+0.099 T 3 mJK −1 mol −1 while, for 4.332K⩽T⩽15.184K, C=28.464T+0.157T 3+55.906 [T 3 2 + 4 5 T 0T 1 2 + 4 15 T 2 0T sol−1 2 . exp (− T 0/ T) in the same units, with T 0=79.3 K. This result indicates that the dispersion relation for magnons in this compound has the form E= k B T 0+ Dk 2. The large energy gap ( k BT 0) is attributed to the high magneto-crystalline anisotropy arising from the unquenched orbital moment of the uranium ions. To our knowledge this is the first energy gap reported for magnons in an actinide compound.