Oxygen plasma-induced enhancement of structural, electrical properties, and thermopower of La${}_{0.5}$Sr${}_{0.5}$MnO${}_3$

Half-doped manganites has proven itself to be candid material for different magnetic-based devises. Various physical properties of pellet size half-doped La${}_{0.5}$Sr${}_{0.5}$MnO${}_3$ manganite treated with oxygen plasma and its comparison with the pristine samples is reported in this article. The impact of plasma irradiation on different properties such as structure, thermoelectric power and electrical resistivity were studied and compared before exposure. The crystal structure or symmetry remains unaffected due to plasma exposure. The Mn${}^{4+}$/Mn${}^{3+}$ ratio decreases after exposing to plasma compared to the pristine samples. It is observed that La${}_{0.5}$Sr${}_{0.5}$MnO${}_3$ samples exhibit insulating behaviour before and after plasma exposure. The resistivity increases appreciably after plasma treatment which may be credited to the reduction in the bond angle of Mn-O-Mn as well as the creation of oxygen vacancies. The negativity of the thermopower is seen at all temperatures attributing it to the electrons behaving as the dominant charge carriers and also shows that the magnitude is temperature dependent.