Spin-glass and variable range hopping quantum interference magnetoresistance in FeSr sub(2)Y sub(1.3)Ce sub(0.7)Cu sub(2)O sub(10-x)

Electronic transport and magnetic measurements have been made on FeSr sub(2)Y sub(1.3)Ce sub(0.7)Cu sub(2)O sub(10-x). We observe a spin-glass at ~23K and a magnetoresistance that reaches -22% at 8 T. The magnetoresistance is due to variable range hopping quantum interference where at low temperatures each hop is over a large number of scatterers. This magnetoresistance is negative at and above 5 K and can be described by the Nguen, Spivak, and Shklovskii (NSS) model. However, there is an increasingly positive contribution to the magnetoresistance for temperatures below 5 K that may be due to scattering from localized free spins during each hop that is not accounted for in the NSS model.