1. Pseudogap formation and vacancy ordering in the new perovskite boride Zr2Ir6B
- Author
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Rachid St. Touzani, Louis-S. Bouchard, Boniface P. T. Fokwa, Dimitrios Koumoulis, and Jan P. Scheifers
- Subjects
Superconductivity ,Materials science ,Polymers and Plastics ,Condensed matter physics ,Fermi level ,Metals and Alloys ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Electronic, Optical and Magnetic Materials ,chemistry.chemical_compound ,symbols.namesake ,chemistry ,Negative thermal expansion ,Boride ,Vacancy defect ,0103 physical sciences ,Ceramics and Composites ,symbols ,010306 general physics ,0210 nano-technology ,Pseudogap ,Superstructure (condensed matter) ,Perovskite (structure) - Abstract
Non-oxide perovskites exhibit unusual properties such as negative thermal expansion, negative thermal coefficient of resistance, positive and negative giant magnetoresistance as well as superconductivity. These uncommon properties appear to originate from the basic structure only, in strong contrast to the oxides. Ordering in nonstoichiometric compounds may not only lead to different chemical compositions but also to the promotion of these physical properties. We present a combined NMR and first-principles study of the cubic Zr 2 Ir 6 B perovskite to investigate the boron ordering with boron deficiency leading to the formation of superstructure. Competing ionic and metallic interactions reflect the semimetallic character of this boride and result in the formation of a pseudogap, as predicted by our first principles calculations and verified experimentally by 11 B solid state NMR. Several avoided crossing scenarios were also found for the bands from the conducting states at +1 eV to the Fermi level along specific directions. This observation is of paramount importance for understanding the structure-property relationships in metal boride perovskites and the search for new cubic perovskites.
- Published
- 2016