Pseudogap formation and vacancy ordering in the new perovskite boride Zr2Ir6B

• Published in: Acta materialia Vol. 120; pp. 32 - 39
• Main Authors: Koumoulis, Dimitrios, Scheifers, Jan P., St. Touzani, Rachid, Fokwa, Boniface P.T., Bouchard, Louis-S.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.11.2016
• Subjects: Boride; Borides; Boron; Double perovskite; Electronic pseudogap; Formations; NMR; Nuclear magnetic resonance; Order disorder; Perovskites; Searching; Thermal expansion; Vacancy ordering; Double perovskite; NMR; Vacancy ordering; Boride; Electronic pseudogap
• ISSN: 1359-6454; 1873-2453
• DOI: 10.1016/j.actamat.2016.08.031

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 Zr2Ir6B 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 11B 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. [Display omitted]