Investigation of magnetic properties and colossal magnetoresistance in nanocrystalline doped manganite

Abstract

Here in, we report structural, magnetic, and magneto-transport properties of nanocrystalline La0.6Ag0.2Bi0.2MnO3 prepared using citrate sol-gel method. By using scanning and transmission electron microscopy measurements, the morphology and particle size of the sample have been confirmed. The Mn2p XPS spectra revealed the nanoparticles contained the coexistence of Mn3+ and Mn4+ ions with Mn3+/Mn4+ ratio of 2:1. Field-cooled and zero field-cooled magnetization protocols with temperature span of 5 K – 300 K, confirm the paramagnetic to ferromagnetic phase transition at critical temperature, TC~146 K. The complete investigation of isothermal magnetization (130≤T (K)≤160,∆T=2 K), Arrott plots, and magnetocaloric effect as well as quantitative analysis of second-order phase transition has been studied. The criticality at the paramagnetic-ferromagnetic transition was examined for the sample, and the obtained critical exponents were verified for their reliability through the utilization of the scaling hypothesis and Kouvel - Fisher plot. We observed a large magnetic entropy change (~7 J-Kg-1K-1) at TC upon 5 T magnetic field strength. The renormalized magnetic entropy change plots are found to collapse onto a single curve, thus verifying the universality of the sample. Above the metal-insulator transitions the electrical resistivity shows a small polaron hopping conduction mechanism, however, at low temperatures scattering mechanism dominates and the whole range was explained by the universal percolation model. The colossal value of negative MR is found to be 88% at 168 K under an applied field strength of 2 T. As a result of our experimental data, we can grasp the intuitive understanding of magnetic as well as transport properties in Bi-doped manganite systems potential for magnetic sensors and spintronics applications.