Study of La-deficient La1-x□xMnO3-δ perovskites with giant magnetoresistance in the composition x = 0.2

• Published in: Phase transitions Vol. 68; no. 2; pp. 399 - 410
• Main Authors: Laroussi, L., Boudaya, C., Dhahrp, E., Joubert, J. C., Pierre, J., Cheikh-Rouhou, A.
• Format: Journal Article
• Language: English
• Published: Reading Taylor & Francis Group 01.03.1999; Taylor and Francis
• Subjects: 1-x; 3-δ; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Exact sciences and technology; Giant magnetoresistance; Magnetic properties and materials; Magnetotransport phenomena, materials for magnetotransport; MnO; Perovskite oxides; Physics; Self-doped La; Lanthanum oxides; Annealing; Self doping; Inorganic compounds; Electrical conductivity; Magnetization; Phase transformations; Ternary compounds; Transition element compounds; Giant magnetoresistance; Perovskites; XRD; Rare earth compounds; Experimental study; Fabrication property relation; Manganese oxides; Quantity ratio; Sintering; Ferromagnetic-paramagnetic transitions
• ISSN: 0141-1594; 1029-0338
• DOI: 10.1080/01411599908224522

Magnetic, structural and electrical properties in self-doped La 1-x □ x MnO 3-δ system are studied. X-ray diffraction shows that the materials with a composition range x = 0.0 -0.33 are single-phase perovskite-like compounds. Depending on sintering temperature and cooling speed, La-deficient phases undergo a complete transformation from orthorhom-bic to rhombohedral symmetry at high Mn 4+ content. These phases exhibit a ferromagnetic to paramagnetic transition with increasing temperature (except for LaMnO 3 which is antiferromagnetic (M ≈ 2 emu/g) at 115 K). On annealing at low temperature (800°C), the structural transition is accompanied by an important increase in both magnetization M and Curie temperature T c . These experimental facts show a close relation of oxygen stoichiometry and Mn 4+ stability with synthesis conditions. A sharp drop in resistivity and a magnetoresistance value (p 0 -P5T)/PO of 85% are observed close to T c = 268 K, for an annealed sample with x = 0.2.