Effect of the calcination temperature on the magnetic and transport properties of rhombohedral LaMnO3+δ compounds

✍ Scribed by X.L. Wang; D. Li; C.X. Shi; B. Li; T.Y. Cui; Z.D. Zhang

• Publisher: Elsevier Science
• Year: 2010
• Tongue: English
• Weight: 903 KB
• Volume: 405
• Category: Article
• ISSN: 0921-4526
• DOI: 10.1016/j.physb.2009.12.001

✦ Synopsis

Rhombohedral LaMnO 3 + d powders were successfully synthesized by annealing gel precursors obtained by a polymerized complex method. The average grain size increases with increasing calcination temperature. The zero-field-cooled (ZFC) and field-cooled (FC) magnetization curves indicate that LaMnO 3 + d compounds obtained at 700 and 800 1C are ferromagnetic, while both ferromagnetic and antiferromagnetic components are present in those calcined at 900 and 1000 1C. This is because the concentration of Mn 4 + ions drops with increasing calcination temperature. The temperature dependence of the resistivity of LaMnO 3 + d compounds exhibits an insulator-metal transition at about 90 K and also a low-temperature upturn with a resistivity minimum at about 40 K. Upon increasing particle size, the zero-field resistivity of the LaMnO 3 + d powders increases due to suppression of the conduction by the insulating antiferromagnetic component. The negative magnetoresistance of a sample pellet prepared at 700 1C ranges from À 82% to À 88% in the temperature range of 40-100 K due to suppression of the spin-dependent scattering by an applied field.