Magnetic Properties Tuning via Broad Range Site Deficiency in Square Net Material UCuBi₂

Area of Science:

• Condensed Matter Physics
• Materials Science
• Solid-State Chemistry

Background:

• HfCuSi2-type pnictogen compounds are known platforms for topologically nontrivial band structures.
• Achieving topological properties requires precise electron count control, typically via A2+M2+Pn2 and A3+M+Pn2 charge distributions.
• Lanthanide-based compounds are studied for topological magnetism, but heavy element analogs like uranium remain underexplored.

Purpose of the Study:

• To synthesize and characterize uranium copper bismuth (UCuBi2) single crystals.
• To investigate the magnetic properties of UCuBi2 and their dependence on composition.
• To explore the potential of site deficiency as a tuning parameter for topological materials.

Main Methods:

• Single crystal growth using a flux method.
• Detailed structural analysis to determine site deficiency (x in UCu(x)Bi2).
• Magnetic property measurements (e.g., Néel temperature, metamagnetic transitions).
• Density Functional Theory (DFT) calculations to model site deficiency effects.

Main Results:

• Flux-grown UCuBi2 crystals exhibit site deficiency, with x ranging from 0.20 to 0.64.
• Magnetic coupling and Néel temperature (TN) are linearly dependent on Cu site deficiency, varying from 51 K (UCu0.60Bi2) to 118 K (UCu0.30Bi2).
• Higher Cu concentration in UCu0.60Bi2 promotes a metamagnetic transition in magnetically anisotropic crystals.
• DFT calculations successfully model site deficiency in UCu(x)Sb2 and UCu(x)Bi2 systems.

Conclusions:

• Site deficiency in UCuBi2 significantly influences magnetic properties and critical temperatures.
• UCuBi2 serves as a model system for understanding the role of stoichiometry in tuning electronic and magnetic properties.
• This work demonstrates a strategy for tuning Fermi levels in A3+M2+Pn2 phases, expanding their potential as topological materials.