Nd2Ni2MgH8 hydride: Synthesis, structure and magnetic properties

Abstract Hydrogen interaction with intermetallic compound Nd 2 Ni 2 Mg crystallizing in the tetragonal Mo 2 FeB 2 type of structure leads to the formation of hydride/deuteride containing 7.4–8 H(D)/f.u. Hydrogen absorption is accompanied by a monoclinic deformation of the unit cell with the crystal structure data refined from Synchrotron XRD (Sp. gr. P 2 1 / c ; a  = 11.60733(5) A; b  = 7.66057(3) A; c  = 11.78743(5) A, β  = 92.4126(4)°, V  = 1047.194(8) A 3 ) and high resolution powder XRD data. The formed interstitial hydride disproportionates during heating forming NdH 2 . Nd 2 Ni 2 Mg is an antiferromagnet with the Neel temperature T N  ≈ 19 K. Presence of another magnetic phase transition at 14 K together with two metamagnetic transitions indicates a complicated magnetic phase diagram. The hydrogenation reduces T N to 1.0 K.