Universality in the magnetic response of metamagnetic metals

Abstract

We report measurements of the nonlinear susceptibility ${\ensuremath{\chi}}_{3}(T)$ in the metamagnetic heavy fermion (HF) compound ${\mathrm{UPt}}_{3}$. At high temperatures, ${\ensuremath{\chi}}_{3}(T)<0$ and is small. It turns positive for $T\ensuremath{\le}35$ K, forms a peak at $T\ensuremath{\cong}10$ K, and then decreases to zero with further decreasing temperature. The peak in $\ensuremath{\chi}{}_{3}$ occurs at a temperature ${T}_{3}$, which is roughly half of ${T}_{1}$, the temperature of the maximum in the linear susceptibility. We present results on ${\mathrm{URu}}_{2}{\mathrm{Si}}_{2}$ and ${\mathrm{UPd}}_{2}{\mathrm{Al}}_{3}$ to show that this feature is common to other HF materials. A two-level model to describe the metamagnetic transition, with separation between the levels being the only energy scale, captures all experimentally observed features.