Tricritical point of the f -electron antiferromagnet USb2 driven by high magnetic fields

In pulsed magnetic fields up to 65 T and at temperatures below the N\'eel transition, our magnetization and magnetostriction measurements reveal a field-induced metamagneticlike transition that is suggestive of an antiferromagnetic to ferrimagnetic ordering. Our data also suggest a change in the nature of this metamagneticlike transition from second- to first-order-like near a tricritical point at ${T}_{\mathrm{tc}}\ensuremath{\sim}145\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ and ${H}_{\mathrm{c}}\ensuremath{\sim}52\phantom{\rule{0.16em}{0ex}}\mathrm{T}$. At high fields for $Hg{H}_{\mathrm{c}}$ we found a decreased magnetic moment roughly half of the moment determined by neutron powder diffraction. We propose that the decreased moment and lack of saturation at high fields indicate the presence of a field-induced ferrimagnetic state above the tricritical point of the H-T phase diagram for $\mathrm{US}{\mathrm{b}}_{2}$.