Magnetic field dependent metal insulator transition by monovalent doping (Na+) in PrMnO3: Investigation through structural, magnetic and transport properties

A detailed study on the structural, magnetic, and transport properties of a monovalent (Na+) doped Pr0.75Na0.25MnO3 (PNMO) compound has been carried out. Temperature (T) and magnetic field (H) dependent magnetization (M), and resistivity (.) measurements have been carried out which reveal a second-order magnetic phase transition around T-C = 60 K accompanied by a metal-insulator transition around T-MI = 138 K. Magnetization measurements also confirm the coexistence of antiferromagnetic (AFM) and ferromagnetic (FM) components in the low-temperature regime. M H has been used to calculate the magnetocaloric behavior and the system is found to show a maximum magnetic entropy change i.e. -Delta S-max as 2.54 J kg(-1).K-1 for the field change of 5 T. Temperature dependence resistivity has been measured under the applied magnetic field and the system exhibits a colossal magnetoresistance (congruent to 81%). Spin-polarized tunneling (SPT) model is applied to explain magnetoresistance (MR) phenomenon under applied magnetic field. Analysis of zero-field resistivity data signifies that a transition from Mott-VRH to Efros-Shklovskii-VRH (ES-VRH) conduction occurs in the low-temperature region in this present PNMO system.