Wide range magnetoresistance through grain size variation in Ag doped lanthanum manganite

Abstract

Monovalent Ag doped lanthanum manganite samples with variable grain sizes were synthesised by standard solid state reaction and sol–gel methods. The nearly monophasic nature is revealed through X-ray diffraction. The process dependent grain sizes were observed in the wide range from 30 nm to 1·2 μm by TEM and SEM. Low temperature resistivity measurement was carried out with 0, 1 and 5 T magnetic fields. The samples with nanosize grains showed metallic behaviour and wide range magnetoresistance. The sample with micrometre size grains showed metal insulator transition and magnetoresistance value up to 85% in the narrow range. Such behaviour may be due to grain boundary and spin dependent scatterings.

Keywords:

• Grain
• Disorders
• CMR
• Sol–gel

The authors are thankful to Dr R. Rawat, UGC-DAE Consortium for Scientific Research and Indore, for their cordial help in MR measurement and SAIF-AIIMS for TEM of our samples. AA and RY are grateful to CSIR for providing SRF to carry out my PhD work.