Different metamagnetism between paramagnetic Ce and Yb isomorphs

TL;DR

This study compares metamagnetic phenomena in isostructural Ce and Yb heavy fermion systems, revealing first-time observations of metamagnetism and contrasting behaviors linked to their electronic states.

Contribution

It reports the first observation of metamagnetism in isomorphic Ce and Yb paramagnetic systems and compares their distinct magnetic responses and underlying mechanisms.

Findings

Metamagnetic-like transition observed in both CeNi₂Ge₂ and YbNi₂Ge₂.

Transition fields scale with the temperature of maximum magnetic susceptibility.

Different nonlinear susceptibility behaviors suggest distinct magnetic natures.

Abstract

To solve the puzzle of metamagnetic phenomena in heavy fermion systems, we have compared paramagnetic isostructural Ce and Yb systems, CeNi$_2$Ge$_2$ and YbNi$_2$Ge$_2$, both of which are located near a magnetic instability. The most intriguing result is discovery of a metamagnetic-like transition in both systems from magnetization measurements in a pulsed magnetic fields. This is the first observation of the metamagnetism for isomorphic Ce and Yb paramagnetic systems. Similar to other metamagnets, the metamagnetic transition fields for both compounds are well scaled by the temperature $T_{\chi}^{\rm max}$, at which the magnetic susceptibility shows a maximum. In addition, for CeNi$_2$Ge$_2$ a peak of nonlinear susceptibility $\chi_3$ appears at approximately $T_{\chi}^{\rm max}/2$, as for other heavy-fermion metamagnets. In contrast, YbNi$_2$Ge$_2$ shows only a sign change for $\chi_3$ at $T_{\chi}^{\rm max}$, as observed in itinerant metamagnets located near the ferromagnetic critical point. The metamagnetism of CeNi$_2$Ge$_2$ corresponds to a typical Kondo lattice system, whereas that of YbNi$_2$Ge$_2$ is similar to the nearly ferromagnetic itinerant systems. Other possibilities for the metamagnetic behavior of YbNi$_2$Ge$_2$ are also discussed.