Insight into the physics of the 5 f -band antiferromagnet U 2 Ni 2 Sn from the pressure dependence of crystal structure and electrical resistivity

A resistivity study of a single crystal of ${\mathrm{U}}_{2}{\mathrm{Ni}}_{2}\mathrm{Sn}$ has been performed at ambient pressure and under hydrostatic pressure up to $p=3.3\phantom{\rule{4pt}{0ex}}\mathrm{GPa}$. It revealed Fermi-liquid behavior accompanied by spin excitations with an energy gap $\mathrm{\ensuremath{\Delta}}=30\text{--}55\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ in the whole pressure range. The N\'eel temperature varies with pressure in a nonmonotonous way. It increases at the rate $d{T}_{\mathrm{N}}/dp=+0.6\phantom{\rule{4pt}{0ex}}\mathrm{K}/\mathrm{GPa}$, and later, after passing through the maximum at \ensuremath{\approx}3 GPa, it starts to decrease quickly. High-pressure x-ray diffraction indicated that an orthorhombic distortion of the tetragonal structure takes place around the pressure of this ${T}_{\mathrm{N}}$ maximum. The computational study based on the density functional theory illustrates that the loss of magnetism in ${\mathrm{U}}_{2}{\mathrm{Ni}}_{2}\mathrm{Sn}$ with pressure is primarily due to $5f$-band broadening, which results from the collapse of the U spacing within the U-U dimers.