Electrical resistivity change due to high-energy X-ray irradiation of oxygen-deficient EuBa2Cu3Oy

High-energy X-ray was irradiated to EuBa2Cu3Oy, which is one of the REBa2Cu3Oy (RE = rare earth) compounds, at low temperature (100 K), and the electrical resistivity was measured in situ at the same temperature (100 K). The X-ray energy was chosen near Cu K-edge (8.98 keV), Eu L3-edge (6.98 keV) and Ba L3-edge (5.25 keV) so that the effect of inner-shell excitation can be detected, if any. The irradiation-induced increase in the electrical resistivity is observed during the irradiations with X-ray in the energy range of 5-9 keV. The electrical resistivity monotonically increases as increasing photon dose. Even if the X-ray is switched off, the irradiation-induced effect remains unchanged. The observed effect has an opposite trend compared with that observed for the visible light irradiation which causes persistent photoconductivity. It is also found that the irradiation-induced increase in resistivity scales with the energy absorbed by EuBa2Cu3Oy. This result indicates that the relaxation process of the energy absorbed by EuBa2Cu3Oy dominates the resistivity increase. The ejection of inner-shell electrons is not the unique cause of the observed effect. The possible origin of the resistivity increase is discussed.