Heat capacity study of the magnetic phases in a Nd$_5$Ge$_3$ single crystal

TL;DR

This study investigates the magnetic phases of Nd$_5$Ge$_3$ using specific heat measurements across a broad temperature and magnetic field range, revealing a gapped $T^2$ contribution and hyperfine effects indicative of magnetic moment flips.

Contribution

It provides new insights into the magnetic excitations and hyperfine interactions in Nd$_5$Ge$_3$, highlighting a gapped $T^2$ term and nuclear level splitting effects.

Findings

Presence of a gapped $T^2$ contribution in both AFM and FM phases.

Observation of a Schottky anomaly from hyperfine splitting of Nd$^{3+}$ ions.

Magnetic-field induced AFM to FM transition involves flipping Nd magnetic moments.

Abstract

The different magnetic phases of the intermetallic compound Nd$_5$Ge$_3$ are studied in terms of the specific heat, in a broad range of temperatures (350~mK--140~K) and magnetic fields (up to 40 kOe). The expected $T^{3}$ and $T^{3/2}$ terms are not found in the antiferromagnetic (AFM) and ferromagnetic (FM) phases respectively, but a gapped $T^2$ contribution that originates from a mixture of AFM and FM interactions in different dimensionalities under a large magnetocrystalline anisotropy, is present in both. An almost identical Schottky anomaly, that arises from the hyperfine splitting of the nuclear levels of the Nd$^{3+}$ ions, is observed in both phases, which leads us to state that the magnetic-field induced transition AFM$\to$FM that the system experiments below $26~\text{K}$ consists in the flip of the magnetic moments of the Nd ions, conserving the average local moment.