Influence of Mn substitution with Co or Fe on transport mechanisms in some manganites

• Published in: Journal of Optoelectronics and Advanced Materials Vol. 10; no. 11; pp. 2924 - 2927
• Main Authors: Craus, M L, Cornei, N, Lozovan, M, Islamov, A
• Format: Journal Article
• Language: English
• Published: 01.11.2008
• ISSN: 1454-4164

Manganites with perovskite structure are today the subject of intensive research, their properties being of fundamental scientific importance and of interest for technological applications. Some manganites, as Lai.xSr.Mn03, are known as ferromagnetic materials, with a 'bad metal' behavior, and a transition temperature close to Curie temperature. The manganites with La0.54Hoo viSr0.35Mni_x(Co/Fe)x03 were prepared by means of sol-gel methods. The treated samples were monitorized by XRD, using a diffractometer preview with a data acquisition system, at room temperature. The XRD data were handled with CeckCell program, to proof the space group and the presence of superstructure, while lattice constants, atom positions in the unit cell, average size of the coherent blocks and microstrains were determinate with Rietveld (PowderCell and GSAS) programs. Magnetic properties of the samples were investigate with a Foner type magnetometer, between 77 and 400 K, using a magnetic field H=4 kOe. Magnetoresistance data were obtained with a four probe method, in a magnetic field Hmax = 20 kOe, between 7 and 300 K. Treated samples contain only perovskite type phases, depending on the Mn substitution. Curie temperature has a maximum value for the smallest amount of Co/Fe. The transition temperature are smaller as Curie temperature with 70 -100 K. Transport mechanisms are discussed, in agreement with the Fe/Co doping. The effect of Co/Fe substitution on the magnetic/crystalline structure of La0.54HomiSro.35Mni.x(Co/Fe)x03 manganites was investigated.