Magnetic properties of a layered cobaltite Sr$_{1-x}$Y$_{x}$CoO$_{3-\delta}$ ($x$ = 0.1)

The structure, the magnetic and magnetotransport properties of perovskite Sr$_{0.9}$Y$_{0.1}$CoO$_{2.63}$ have been studied. The sample is shown to have a two-phase structure. The main phase has a tetragonally distorted unit cell and is described by space group $I4/mmm$. The broadening of the reflections with indices corresponding to doubling unit cell parameter c indicates the absence of the rigorous translation symmetry along axis $c$. The existence of the broadened superstructure reflection observed in the diffraction pattern at small angles at temperature lower than 400 K is explained by the existence of the monoclinic phase whose content is significantly lower than that of the tetragonal phase, but is dominant in the Sr$_{1-x}$Y$_{x}$CoO$_{3-\delta}$ composition. The spontaneous magnetization appears as the monoclinic phase forms. The magnetic structure is mainly $G$-type antiferromagnetic with magnetic moments 1.5$\mu_{\operatorname{B}}$ in the layers of CoO$_6$ octahedra and 2$\mu_{\operatorname{B}}$ in the anion-deficit CoO$_{4+\gamma}$ layers. The conduction of the Sr$_{0.9}$Y$_{0.1}$CoO$_{2.63}$ composition has a semiconducting character. The magnetoresistance is 57% in a field of 14 T at a temperature of 5 K and strongly decreases with the temperature increase.