Unusual signatures of the ferromagnetic transition in the heavy Fermion compound UMn$_2$Al$_{20}$

TL;DR

This paper investigates the magnetic properties of the heavy fermion compound UMn$_2$Al$_{20}$, revealing an unusual ferromagnetic transition with weak thermodynamic signatures, suggesting either itinerant or induced local moment ferromagnetism.

Contribution

It provides comprehensive experimental data on UMn$_2$Al$_{20}$, including magnetization, specific heat, resistivity, and neutron diffraction, highlighting its atypical ferromagnetic transition behavior.

Findings

Ferromagnetic transition at 20 K in UMn$_2$Al$_{20}$

Weak specific heat anomaly at T_c

No resistivity anomaly at T_c

Abstract

Magnetic susceptibility results for single crystals of the new cubic compounds UT$_2$Al$_{20}$ (T=Mn, V, and Mo) are reported. Magnetization, specific heat, resistivity, and neutron diffraction results for a single crystal and neutron diffraction and inelastic spectra for a powder sample are reported for UMn$_2$Al$_{20}$. For T = V and Mo, temperature independent Pauli paramagnetism is observed. For UMn$_2$Al$_{20}$, a ferromagnetic transition is observed in the magnetic susceptibility at $T_c$ = 20 K. The specific heat anomaly at $T_c$ is very weak while no anomaly in the resistivity is seen at $T_c$. We discuss two possible origins for this behavior of UMn$_2$Al$_{20}$: moderately small moment itinerant ferromagnetism, or induced local moment ferromagnetism.