A Novel Mixed Valent Chromium-Layered Oxide with Peculiar Magnetic Properties: Sr4.5Cr2.5O9

• Published in: Journal of solid state chemistry Vol. 154; no. 2; pp. 375 - 383
• Main Authors: Pelloquin, D., Wahl, A., Masset, A.C., Maignan, A., Michel, C., Raveau, B.
• Format: Journal Article
• Language: English
• Published: San Diego, CA Elsevier Inc 01-11-2000; Elsevier
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Exchange and superexchange interactions; Inorganic compounds; Magnetic properties and materials; Magnetically ordered materials: other intrinsic properties; Physics; Saturation moments and magnetic susceptibilities; Structure of solids and liquids; crystallography; Structure of specific crystalline solids; Temperature dependence; Intergrowth; Inorganic compounds; Mixed-valence compounds; Magnetization; Transition element compounds; Oxides; XRD; High temperature; Experimental study; Magnetic transitions; High-resolution methods; Structural models; Magnetic susceptibility; Metamagnetism; Strontium oxides; Lamellar structure; Chromium oxides; Chemical preparation; TEM; Low temperature; Crystal structure
• ISSN: 0022-4596; 1095-726X
• DOI: 10.1006/jssc.2000.8798

A new mixed valent chromium-layered oxide, Sr4.5Cr2.5O9, with a structure closely related to the “0201–1201” structure of the superconducting cuprate TlBa2−xLa2+xCu2O9, has been synthesized at normal pressure. This orthorhombic phase (a=10.7959(2) Å, b=5.4012(1) Å, and c=30.0755(6) Å) consists of the regular intergrowth of [Sr2CrO4]0201 blocks and [(Sr0.5Cr0.5)Sr2CrO5]1201 blocks. It differs from the thallium cuprate by the 1:1 ordering of Sr and Cr species within the intermediate layer of the “1201” block, so that at this level CrO4 tetrahedra, containing Cr6+ species, are obtained. Moreover, at the boundary between the “1201” and “0201” blocks, CrO6 octahedra alternate with CrO5 pyramids, both occupied by Cr3+ species. The magnetic measurements show an original metamagnetic transition from an antiferromagnetic to a weak ferromagnetic state. These properties are interpreted in terms of strong intralayer and weak interlayer magnetic couplings between Cr3+ species through a superexchange mechanism.