Abstract
U2Ni2Sn is a member of a large family of intermetallic compounds with the tetragonal Mo2FeB2 crystal structure. It orders antiferromagnetically at 25 K with propagation vector q=(0,0,12). Magnetization, magnetoacoustic, and neutron-diffraction experiments on a single crystal provide evidence that the uranium moments align parallel to the c axis with the anisotropy energy of ≈170 K, indicating that U2Ni2Sn can be classified as an Ising system. The results are at variance with previous studies on polycrystals, which indicated different magnetic structure, and which were incompatible with the 5f−5f two-ion anisotropy model dominant in most U band systems. High-field magnetization studies exhibit a weak linear response for fields along the basal plane up to the highest field applied (60 T), while the c-axis magnetization curve exhibits three metamagnetic transitions at approximately 30, 39, and 50 T. The U magnetic moments of 0.87μB, the low magnetic entropy, and the enhanced Sommerfeld coefficient γ=187mJ/molf.u.K2 suggest that U2Ni2Sn can be classified as an itinerant antiferromagnet with strong electron-electron correlations.
