Itinerant Magnetism in Hydride-Synthesized CaCo₁₂B₆

Area of Science:

• Materials Science
• Solid State Chemistry
• Computational Materials Science

Background:

• Exploration of the Ca-Co-B phase space is underexplored for novel material discovery.
• Computational predictions from the Open Quantum Materials Database (OQMD) suggested thermodynamic stability for CaCo12B6.
• Traditional synthesis routes for similar compounds can be lengthy and yield lower purity.

Purpose of the Study:

• To synthesize and characterize a new ternary compound, CaCo12B6, predicted by computational methods.
• To investigate the viability of a hydride synthesis route for alkaline-earth-transition metal borides.
• To determine the structural, thermal, and magnetic properties of the newly discovered CaCo12B6.

Main Methods:

• High-throughput computations using the Open Quantum Materials Database (OQMD).
• Synthesis of CaCo12B6 using calcium hydride (CaH2) and various boron precursors.
• Powder X-ray diffraction (PXRD) for structural analysis, including high-temperature in situ studies.
• Density functional theory (DFT) calculations for electronic structure.
• X-ray absorption near-edge spectroscopy (XANES) and Bader charge analysis for electronic characterization.
• Magnetometry for magnetic property determination.

Main Results:

• Successful synthesis of CaCo12B6 in the SrNi12B6 structure type (R-3m, #166) with high purity and short synthesis duration.
• CaCo12B6 is water- and air-stable and thermally stable up to 1050 K under vacuum.
• DFT calculations predict a metallic ground state with ferromagnetic properties.
• Magnetometry reveals room-temperature paramagnetism (μeff = 1.7(1)μB/Co) and ferromagnetic ordering below 172(1) K.

Conclusions:

• The hydride route using CaH2 is an effective and efficient strategy for synthesizing novel ternary alkaline-earth-transition metal borides.
• CaCo12B6 is a newly discovered stable ternary boride with interesting metallic and ferromagnetic characteristics.
• This work validates the predictive power of computational databases like OQMD for materials discovery.