Band structures, magnetic properties, and enhanced magnetoresistance in the high pressure phase of Gd and Y doped two-dimensional perovskite Sr2CoO4 compounds

The authors present their studies on the band structures and on the magnetic and magnetotransport properties of the high pressure phase of Sr2−xRExCoO4 [rare earth (RE)=Gd and Y, x=0.1–0.5] compounds which were synthesized by a high pressure and high temperature technique. The authors found that as x increases, the magnetoresistance {(ρH−ρ0)∕ρ0} increases up to −17% at 5K and 7T, which is 2.5 times higher than that for undoped Sr2CoO4, although the ferromagnetic transition drops from 255to200K for the Gd doping with x=0.3. The saturation moments at low temperature are significantly enhanced for the Gd doped Sr2CoO4. Observation of a close correlation between resistance and field revealed a strong spin-dependent tunneling magnetoresistance. First-principles band structure calculations indicate that high spin polarization is present for both undoped and doped compounds.