Electrical and Magnetic Properties of Strontium Substituted Lanthanum Manganate Perovskite Crystals Prepared Using Fused Salt Electrolysis

✍ Scribed by W.H. McCarroll; K.V. Ramanujachary; Ian D. Fawcett; M. Greenblatt

• Publisher: Elsevier Science
• Year: 1999
• Tongue: English
• Weight: 180 KB
• Volume: 145
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.1999.8224

✦ Synopsis

Crystals of Sr-doped perovskite lanthanum manganates, containing 7+34 mole percent Sr have been grown by fused salt electrolysis using Cs 2 MoO 4 +MoO 3 solvents in stabilized zirconia crucibles. The rhombohedral crystals grow with cubic-like habits typically with facial areas 0.25+4 mm 2 on edge with the average facial area decreasing with increasing Sr content. All measured crystals with Sr contents between 11.7 and 33.6 mole percent Sr underwent transitions from a paramagnetic-insulator to a ferromagnetic-metallic state with values of T c and T IM between 325 and ' '400 K (for T IM ), the values increasing with Sr content. A magnetoresistance of approximately 45% at 375 K was observed for a crystal of composition Sr 0.336 La 0.661 Mn 0.997 O 3 . The anomalously high T c ‫؍‬ 325 K for Sr 0.117 La 0.844 Mn 0.990 O 3 for a sample of such low Sr content is interpreted in terms of a high vacancy level on the A cation site which stabilizes the rhombohedral perovskite structure, which otherwise might have been expected to be orthorhombic type-1. The formation of Sr-doped lanthanum manganate perovskite at the cathode with the orthorhombic type-2 structure is interpreted in terms of an electrostatically assisted air oxidation mechanism.