A New Unconventional Antiferromagnet, Yb$_3$Pt$_4$

TL;DR

Yb$_3$Pt$_4$ is a newly synthesized compound exhibiting antiferromagnetic order at 2.4 K, characterized by local moments, a gapped Fermi surface, and unconventional magnetic and electronic properties.

Contribution

This paper reports the synthesis and characterization of Yb$_3$Pt$_4$, revealing its unique magnetic order and electronic behavior distinct from typical heavy fermion systems.

Findings

Yb ions are fully trivalent with a doublet ground state.

Antiferromagnetic order occurs at 2.4 K with a large entropy change.

Electrical resistivity becomes quadratic at the Neel temperature.

Abstract

We report the synthesis and basic properties of single crystals of a new binary compound, Yb$_{3}$Pt$_{4}$. The Yb ions in this compound are fully trivalent, and heat capacity measurements show that the crystal field scheme involves a doublet ground state, well separated from the excited states, which are fully occupied above $\sim$ 150 K. The heat capacity displays a large, weakly first order anomaly at 2.4 K, where a cusp is observed in the magnetic susceptibility signalling the onset of antiferromagnetic order. The entropy associated with this order is the full Rln2 of the doublet ground state, however the magnetic susceptibility in the ordered phase is dominated by a large and temperature independent component below the Neel temperature. The heat capacity in the ordered state originates with ferromagnetic spin waves, giving evidence for the inherently local moment character of the ordered state. The electrical resistivity is unusually large, and becomes quadratic in temperature exactly at the Neel temperature. The absence of analogous Fermi liquid behavior in the heat capacity and the magnetic susceptibility implies that Yb$_{3}$Pt$_{4}$ is a low electron density system, where the Fermi surface is further gapped by the onset of magnetic order.