The Doppler broadening lineshape of 5llkeV gamma rays of positron annihilation radiation in the high Tc superconductors Y-Ba-Cu-O has been investigated.The lineshape parameters as a function of temperature were measur...The Doppler broadening lineshape of 5llkeV gamma rays of positron annihilation radiation in the high Tc superconductors Y-Ba-Cu-O has been investigated.The lineshape parameters as a function of temperature were measured from 85K to 300K.Anomalous dependence of lineshape parameters on temperature was first observed in polyphase samples,i.e.,the lineshape parameters occurred catastrophe for some narrow temperature regions(90K.107K,115K and 180K).This anomaly is probably due to the migration and redistribution of oxygen vacancies in the samples during superconducting transition.展开更多
THE colossal magnetoresistance (CMR) effects in doped perovskite-like oxide have stimulatedconsiderable attention to the study of fundamental physics and the application of new type ma-terials. It was reported that a ...THE colossal magnetoresistance (CMR) effects in doped perovskite-like oxide have stimulatedconsiderable attention to the study of fundamental physics and the application of new type ma-terials. It was reported that a large CMR effect and a high critical temperature T_c shown展开更多
文摘The Doppler broadening lineshape of 5llkeV gamma rays of positron annihilation radiation in the high Tc superconductors Y-Ba-Cu-O has been investigated.The lineshape parameters as a function of temperature were measured from 85K to 300K.Anomalous dependence of lineshape parameters on temperature was first observed in polyphase samples,i.e.,the lineshape parameters occurred catastrophe for some narrow temperature regions(90K.107K,115K and 180K).This anomaly is probably due to the migration and redistribution of oxygen vacancies in the samples during superconducting transition.
文摘THE colossal magnetoresistance (CMR) effects in doped perovskite-like oxide have stimulatedconsiderable attention to the study of fundamental physics and the application of new type ma-terials. It was reported that a large CMR effect and a high critical temperature T_c shown