Mossbauer Study of Materials Displaying Colossal Magnetic Resistivity

摘要

In the last decade the discovery of colossal magnetoresistance in Mn based perovskites brought various perovskite and spinel materials, displaying the effect of magnetoresistance, into the center of scientific interest. The physical and chemical effects, underlying the phenomenon of negative magnetoresistance in these compounds, are not yet fully understood. In this article we investigate the local electronic and magnetic state of iron in three different type of perovskite and spinel compounds: the double perovskite Sr_2Fe_(1+x)Mo_(1-x)O_6 with an excess of iron (x approx= 0.12), the perovskite La_(0.8)Sr_(0.2)Fe_(0.3)Co_(0.7)O_(3-z), and the chalcogenide spinel FeCr_2S_4.