Spin fluctuations in hydrogen-stabilized Laves phase UTi₂H₅

ABSTRACT

Uranium Laves phase UTi₂ does not exist in a pure form, but can be stabilised by the presence of hydrogen, which can be absorbed in concentration exceeding 5 H atoms/f.u. Low temperature specific heat, magnetic susceptibility, and resistivity indicate that UTi₂H₅ is a spin fluctuator close to the verge of magnetic ordering. Its susceptibility follows at high temperatures the Curie–Weiss law with U effective moment µ_eff[  =  3.1 µ_B/U and paramagnetic Curie temperature Θ_p  =  −200 K. The temperature dependence of specific heat exhibits a pronounced and weakly field dependent upturn in C_p/T versus T below 10 K reflecting the effect of spin fluctuations. It can be described by an additional T^½ term. The Sommerfeld coefficient γ  =  256 mJ/mol K² classifies the compound as a mid-weight heavy fermion. Spin fluctuations are affecting also electrical and thermal transport and thermoelectric power, which all resemble UAl₂. A lattice anomaly at ≈ 240 K, attributed to the melting of hydrogen sublattice, reflects in most of bulk properties.

KEYWORDS:

• Uranium compounds
• Laves phase
• transport properties
• heavy-fermion metals
• specific heat
• magnetization dynamics

Acknowledgments

This work was supported by the Czech Science Foundation under the Grant 18-02344S. The study of the crystal structure was supported by the project NanoCent - Nanomaterials centre for advanced applications, project no. CZ.02.1.01/0.0/0.0/15_003/0000485, financed by the ERDF. Authors are indebted to T. Yamamoto for a fruitful discussion.

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Silvie Mašková http://orcid.org/0000-0002-0154-7951

Additional information

Funding

This work was supported by European Regional Development Fund: [Grant Number CZ.02.1.01/0.0/0.0/15_003/0000485]; Czech Science Foundation: [Grant Number 18-02344S].