Increase in Electric Conductivity of YbFe 2 O 4 under Ar laser Irradiation

We measured electric conductivity of YbFe2O4 poly crystal under Ar (488 nm, 2.54 eV) and He-Ne (632.8 nm, 1.96 eV) lasers. In order to discuss only photoconductive effect, sample temperature was measured during the electric measurement. The electric conductivity increases exponentially with increase of Ar laser intensity in isothermal process, despite that electric conductivity increases proportionately to light intensity in general semiconductor. This abnormal photoconductivity implies exponential increase of number of electric carrier by melt of charge order.