Spontaneous Generation of Voltage in Sm0.55Sr0.45MnO3 and La0.75Ba0.25MnO3 Single Crystals

Abstract

In Sm0.55Sr0.45MnO3single crystals, grown by the floating-zone method with the cooling in oxygen, has been observed the spontaneous generation of voltage (SGV). Its maximum reaches 60 μV and occurs in the temperature range where simultaneous decay of the CE-type antiferromagnetic order and the charge order take place in some clusters. The SGV peak becomes lower by about 45% if magnetic field 14.2 kOe applied. Also we observed the SGV in La0.75Ba0.25MnO3single crystals. Maximum value of SGV occurs in a vicinity of the Curie temperature. The SGV value seems to be almost independent from the cooling or heating rate and crystallographic direction, but in La0.75Ba0.25MnO3it is smaller than in Sm0.55Sr0.45MnO3by an order of magnitude. La0.75Ba0.25MnO3compound contains ferromagnetic clusters, in which the electrical charges are localized according to gain in thes-dexchange energy. They are distributed in the paramagnetic lattice, impoverished of an electrical charge. It is shown that SGV stems from the presence of regions with different electrical charges in both samples.