Possible canted antiferromagnetism in UCu$_9$Sn$_4$

TL;DR

This paper reports the discovery of a new uranium-based compound UCu9Sn4 exhibiting complex magnetic phase transitions, including possible canted antiferromagnetism, with detailed structural and magnetic characterization.

Contribution

The study introduces UCu9Sn4 as a new compound with unique magnetic behavior, including multiple phase transitions and evidence for canted antiferromagnetism, expanding understanding of uranium intermetallics.

Findings

Valence transition at 105 K with entropy change of 0.5 Rln2

Possible onset of helical spin order at 32 K

Evidence of canted antiferromagnetism at low temperatures

Abstract

We report on the new compound UCu${}_9$Sn${}_4$ which crystallizes in the tetragonal structure \emph{I}4/\emph{mcm} with lattice parameters $a = 8.600{\rm\AA}$ and $c = 12.359{\rm\AA}$. This compound is isotyp to the ferromagnetic systems RECu${}_9$Sn${}_4$ (RE = Ce, Pr, Nd) with Curie temperatures $T{}\rm_C$ = 5.5 K, 10.5 K and 15 K, respectively. UCu${}_9$Sn${}_4$ exhibits an uncommon magnetic behavior resulting in three different electronic phase transitions. Below 105 K the sample undergoes a valence transition accompanied by an entropy change of 0.5 Rln2. At 32 K a small hump in the specific heat and a flattening out in the susceptibility curve probably indicate the onset of helical spin order. To lower temperatures a second transition to antiferromagnetic ordering occurs which develops a small ferromagnetic contribution on lowering the temperature further. These results are strongly hinting for canted antiferromagnetism in UCu${}_9$Sn${}_4$.