CeMnNi4: an impostor half-metal

TL;DR

This paper challenges the classification of CeMnNi4 as a half-metal, revealing it is actually a semimetal with unique phonon and transport properties, including potential for high thermoelectric efficiency.

Contribution

It provides first-principles calculations showing CeMnNi4 is a semimetal, not a half-metal, and predicts unusual phonon and transport behaviors.

Findings

CeMnNi4 is a semimetal, not a half-metal.

Unusual phonon modes with low-frequency Mn rattling.

High thermoelectric figure of merit (ZT) predicted).

Abstract

Recent experiments show CeMnNi$_{4}$ to have a nearly integer magnetic moment and a relatively large transport spin polarization, as probed by Andreev reflection, suggesting that the material is a half metal or close to it. However, the calculations reported here show that it is not a half metal at all, but rather a semimetal of an unusual nature. Phonon properties should also be quite unusual, with rattling low-frequency Mn modes. Nontrivial transport properties, including a large thermolectric figure of merit, $ZT,$ are predicted in the ferromagnetic state of the well ordered stoichiometric CeMnNi$_{4}$