Sr 2 Pt 8- x As: a layered incommensurately modulated metal with saturated resistivity

• Published in: IUCrJ Vol. 5; no. Pt 4; pp. 470 - 477
• Main Authors: Martino, Edoardo, Arakcheeva, Alla, Autès, Gabriel, Pisoni, Andrea, Bachmann, Maja D, Modic, Kimberly A, Helm, Toni, Yazyev, Oleg V, Moll, Philip J W, Forró, László, Katrych, Sergiy
• Format: Journal Article
• Language: English
• Published: England 01.07.2018
• Subjects: vacancies; inorganic materials; incommensurately modulated structure; density functional theory; platinum-based metallic compounds; Mooij correlation; composite materials
• ISSN: 2052-2525; 2052-2525
• DOI: 10.1107/S2052252518007303

The high-pressure synthesis and incommensurately modulated structure are reported for the new compound Sr Pt As, with = 0.715 (5). The structure consists of Sr Pt As layers alternating with Pt-only corrugated grids. calculations predict a metallic character with a dominant role of the Pt electrons. The electrical resistivity (ρ) and Seebeck coefficient confirm the metallic character, but surprisingly, ρ showed a near-flat temperature dependence. This observation fits the description of the Mooij correlation for electrical resistivity in disordered metals, originally developed for statistically distributed point defects. The discussed material has a long-range crystallographic order, but the high concentration of Pt vacancies, incommensurately ordered, strongly influences the electronic conduction properties. This result extends the range of validity of the Mooij correlation to long-range ordered incommensurately modulated vacancies. Motivated by the layered structure, the resistivity anisotropy was measured in a focused-ion-beam micro-fabricated well oriented single crystal. A low resistivity anisotropy indicates that the layers are electrically coupled and conduction channels along different directions are intermixed.