UC Riverside

The combination of computation and experiment is vital to the efficient and thorough study of magnetic materials. Computation allows us to determine the preferred magnetic state of a given model, and techniques including Density of States (DOS) and the Crystal Orbital Hamilton Population (COHP) will explain what orbitals dominate at the fermi energy, and if there are any electronic instabilities. This enables us to efficiently use our time in the experimental lab by predicting novel magnetic materials with Density Functional Theory (DFT) before synthesizing them. The structures discovered weresynthesized by arc-melting and further characterized by X-Ray diffraction, Energy Dispersive X-Ray (EDX) analysis, and magnetic measurements.

The quaternary Hf2MOs5B2 (M = Mn, Fe, or Co) compositions, belonging to the Ti3Co5B2 structure type, were first studied. Magnetic measurements confirmed the DFT predictions that Hf2MnOs5B2 and Hf2FeOs5B2 exhibit semi-hard and hard-magnetic behaviors, respectively, with coercivity values of 10.0 kA/m and 49.9 kA/m at 5 K. Prior to this study, all semi-hard and hard magnets of this structure type had a group 9 transition metal. Replacing the group 9 transition metal with osmium illustrates that osmium can also be used to create hard magnets. However, the computational data alsoillustrated there is the possibility of creating harder magnets by incorporating osmium and a group 9 metal. Based on this knowledge and other recent literature, the compositions Hf2MOs4IrB2 and Hf2MOs3Ir2B2 (M = Mn, Fe) were computationally investigated and confirmed the hypothesis that a harder magnet can be obtained by incorporating iridium.

TiFe1.3Os3.9B2.8 is the first quaternary composition of the NbRuB structure type, and the third quaternary composition containing titanium, iron, osmium, and boron. Theory predicted a preference for magnetic ordering which was confirmed qualitatively when the material was synthesized. As a result of this magnetic material, the NbRuB structure type, which was previously known for the NbRuB superconductor, is now also of interest for studying magnetism. TiIrB was also synthesized and crystallizes in the Ti1+xRh2−x+yIr3−yB3 structure type. Upon synthesis, computation was utilized to understand the electronic structure of this ternary composition containing B4 zigzag units.