Impact of Oxygen Plasma Treatment on the Structural, Electrical and Magnetic Properties of La 0.7 Ba 0.3 MnO 3

This study investigates the impact of extended oxygen plasma exposure for the duration of 60, 90 and 180 seconds (s) on the structural, electrical and magnetic properties of La0.7Ba0.3MnO3 (LBMO) manganite. LBMO powder samples were prepared using the conventional solid-state reaction method. Rietveld refinement of X-ray diffraction data confirmed that all samples crystallize in a Rhombohedral structure. Bond angle Mn-O-Mn shows a significant variation after plasma exposure whereas Mn-O bond length increases slightly for 90 and 180 s plasma exposure. The temperature-dependent resistivity plot shows two distinct metal-insulator transitions, Tp1 and Tp2. An increase in resistivity is observed with 60 seconds plasma exposure, but with prolonged plasma exposure duration of 90 and 180 seconds, a reduction in resistivity follows. The low-temperature region, T<Tp2, is well described by a metallic model, whereas for temperatures above Tp2, Mott’s Small Polaron Hopping and Variable Range Hopping mechanisms dominate conduction process. The temperature dependent zero-field-cooled and field-cooled 29magnetization measurements, taken from 5 K to 300 K, shows a distinct drop in magnetization near 200 K for all the samples which is suppressed after applying 100 Oe magnetic field. After 60 seconds of plasma exposure, the overall magnetization decreases, but with extended exposure durations, the magnetization value increases. Field dependent magnetization isotherms taken at 6 K and 300 K reveal ferromagnetic behaviour for all the samples.