Low temperature spin polarized tunnelling magneto-resistance in La1-xCaxMnO3 (x=0.375 and 0.625) nanoparticles
The structural, electrical and magneto-transport properties of the La1-xCaxMnO3 (x = 0.375 and 0.625) nanoparticles (~ 50 nm) synthesized by the sol-gel method have been reported. X-Ray diffraction pattern recorded at room temperature confirms the growth of the samples in a single phase. In the absence of magnetic field, a metal to insulator (MI) transition is observed in x = 0.375 sample at 172 K (TMI), while the x = 0.625 sample shows a charge ordered (CO) behaviour at temperatures below 150 K (TCO). Both samples show a substantial negative magneto-resistance (MR). The fitting of the field-dependent MR isotherms by scaling law displays linear variation below TMI/TCO and quadratic above TMI/TCO. The fitting result suggests that a significant negative MR at low temperature is due to inter-grain spin polarized tunnelling across grain boundary and domain contribution.
KeywordsNegative magnetoresistance Metal-insulator transition Charge ordering Spin polarized tunnelling
GC (JRF) gratefully acknowledges SERB-DST and AKS (Project fellow) to UGC DAE CSR for fellowship. We thank Dr. Mukul Gupta and Layanta Behera for XRD, Dr. Rajeev Rawat and Sachin Kumar for resistivity/MR measurements at UGC-DAE Consortium for Scientific Research, Indore.
This work is supported by UGC DAE CSR, Indore (CSR-IC/CRS-89/2014-2018) and SERB-DST, New Delhi (EMR/2016/005424) granted to VD.
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