Anisotropic colossal magnetoresistance effects in Fe1-xCuxCr2S4 -: art. no. 144419

A detailed study of the electronic transport and magnetic properties of Fe1-xCuxCr2S4 (xless than or equal to0.5) on single crystals is presented. The resistivity is investigated for 2less than or equal toTless than or equal to300 K in magnetic fields up to 140 kOe and under hydrostatic pressure up to 16 kbar. In addition magnetization and ferromagnetic resonance (FMR) measurements were performed. FMR and magnetization data reveal a pronounced magnetic anisotropy, which develops below the Curie temperature, T-C, and increases strongly towards lower temperatures. Increasing the Cu concentration reduces this effect. At temperatures below 35 K the magnetoresistance, MR=[rho(0)-rho(H)]/rho(0), exhibits a strong dependence on the direction of the magnetic field, probably due to an enhanced anisotropy. Applying the field along the hard axis leads to a change of sign and a strong increase in the absolute value of the magnetoresistance. On the other hand the magnetoresistance remains positive down to lower temperatures, exhibiting a smeared out maximum with the magnetic field applied along the easy axis. The results are discussed in the ionic picture using a triple-exchange model for electron hopping as well as a half metal utilizing a band picture.