Expanding the homogeneity range of UFe2: Formation of Laves phase UFe2+Ni

Duncan H. Moseley; Jenn Neu; Raphael Hermann; Chad Parish; Josephine Libero-Cruzado; Zachary E. Brubaker

doi:10.1016/j.jallcom.2025.183819

Expanding the homogeneity range of UFe₂: Formation of Laves phase UFe₂+Ni

Duncan H. Moseley, Jenn Neu, Raphael Hermann, Chad Parish, Josephine Libero-Cruzado, Zachary E. Brubaker

Research output: Contribution to journal › Article › peer-review

Abstract

Uranium-based intermetallic Laves phases (UM₂) provide valuable insight into the interplay of 5f orbital hybridization and magnetic properties. However, ferromagnetism in these compounds is rare. UFe₂ is a cubic C15 Laves phase with greatest Curie temperature (T_C) of all such compounds, at 162 K. In this study, we report the synthesis and characterization of a novel U-based Laves phase, UFe₂+Ni, effectively forcing excess Ni in to the UFe₂ structure. UFe₂+Ni crystallizes in the cubic C15 Laves phase, appearing to deviate from the typical UM₂ formula and exhibiting a significantly extended homogeneity range. Annealing this material leads to an increased ferromagnetic transition temperature, between 35 and 155 K, and decreased lattice parameter with higher annealing temperatures. This variation is attributed to changes in Fe and Ni solubility with annealing temperature. Our findings highlight the potential for tuning magnetic properties in U-based Laves phases through compositional and thermal modifications, expanding the understanding of magnetically ordered intermetallics.

Original language	English
Article number	183819
Journal	Journal of Alloys and Compounds
Volume	1042
DOIs	https://doi.org/10.1016/j.jallcom.2025.183819
State	Published - Oct 15 2025

Funding

This research was funded by the US Department of Energy and through the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory, USA . ORNL is managed by UT-Battelle, LLC, under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy (DOE).

Keywords

Annealing effects
C15 Laves phase
Extended stoichiometry
Ferromagnetic transition
Uranium intermetallics

Access to Document

10.1016/j.jallcom.2025.183819

Cite this

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title = "Expanding the homogeneity range of UFe2: Formation of Laves phase UFe2+Ni",

abstract = "Uranium-based intermetallic Laves phases (UM2) provide valuable insight into the interplay of 5f orbital hybridization and magnetic properties. However, ferromagnetism in these compounds is rare. UFe2 is a cubic C15 Laves phase with greatest Curie temperature (TC) of all such compounds, at 162 K. In this study, we report the synthesis and characterization of a novel U-based Laves phase, UFe2+Ni, effectively forcing excess Ni in to the UFe2 structure. UFe2+Ni crystallizes in the cubic C15 Laves phase, appearing to deviate from the typical UM2 formula and exhibiting a significantly extended homogeneity range. Annealing this material leads to an increased ferromagnetic transition temperature, between 35 and 155 K, and decreased lattice parameter with higher annealing temperatures. This variation is attributed to changes in Fe and Ni solubility with annealing temperature. Our findings highlight the potential for tuning magnetic properties in U-based Laves phases through compositional and thermal modifications, expanding the understanding of magnetically ordered intermetallics.",

keywords = "Annealing effects, C15 Laves phase, Extended stoichiometry, Ferromagnetic transition, Uranium intermetallics",

author = "Moseley, \{Duncan H.\} and Jenn Neu and Raphael Hermann and Chad Parish and Josephine Libero-Cruzado and Brubaker, \{Zachary E.\}",

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doi = "10.1016/j.jallcom.2025.183819",

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T2 - Formation of Laves phase UFe2+Ni

AU - Moseley, Duncan H.

AU - Neu, Jenn

AU - Hermann, Raphael

AU - Parish, Chad

AU - Libero-Cruzado, Josephine

AU - Brubaker, Zachary E.

PY - 2025/10/15

Y1 - 2025/10/15

N2 - Uranium-based intermetallic Laves phases (UM2) provide valuable insight into the interplay of 5f orbital hybridization and magnetic properties. However, ferromagnetism in these compounds is rare. UFe2 is a cubic C15 Laves phase with greatest Curie temperature (TC) of all such compounds, at 162 K. In this study, we report the synthesis and characterization of a novel U-based Laves phase, UFe2+Ni, effectively forcing excess Ni in to the UFe2 structure. UFe2+Ni crystallizes in the cubic C15 Laves phase, appearing to deviate from the typical UM2 formula and exhibiting a significantly extended homogeneity range. Annealing this material leads to an increased ferromagnetic transition temperature, between 35 and 155 K, and decreased lattice parameter with higher annealing temperatures. This variation is attributed to changes in Fe and Ni solubility with annealing temperature. Our findings highlight the potential for tuning magnetic properties in U-based Laves phases through compositional and thermal modifications, expanding the understanding of magnetically ordered intermetallics.

AB - Uranium-based intermetallic Laves phases (UM2) provide valuable insight into the interplay of 5f orbital hybridization and magnetic properties. However, ferromagnetism in these compounds is rare. UFe2 is a cubic C15 Laves phase with greatest Curie temperature (TC) of all such compounds, at 162 K. In this study, we report the synthesis and characterization of a novel U-based Laves phase, UFe2+Ni, effectively forcing excess Ni in to the UFe2 structure. UFe2+Ni crystallizes in the cubic C15 Laves phase, appearing to deviate from the typical UM2 formula and exhibiting a significantly extended homogeneity range. Annealing this material leads to an increased ferromagnetic transition temperature, between 35 and 155 K, and decreased lattice parameter with higher annealing temperatures. This variation is attributed to changes in Fe and Ni solubility with annealing temperature. Our findings highlight the potential for tuning magnetic properties in U-based Laves phases through compositional and thermal modifications, expanding the understanding of magnetically ordered intermetallics.

KW - Annealing effects

KW - C15 Laves phase

KW - Extended stoichiometry

KW - Ferromagnetic transition

KW - Uranium intermetallics

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