Magnetic Phase Separation in Oxygen Doped SrCoO$_{3-y}$

SrCoO$_{3-y}$ forms the perovskite structure with oxygen vacancies and is ferromagnetic for y$<$0.25. We have performed a study on polycrystalline samples, controlling the oxidation state using electrochemistry. Under these conditions we have found that magnetically the system segregates into separate, stable phases that correspond to SrCoO$_{2.75}$(T$_{C}$ = 165 K), SrCoO$_{2.875 }$(T$_{C}$ = 220 K), and SrCoO$_{3}$ (T$_{C}$ = 280 K), with two phase behavior for intermediate oxygen concentrations. Surprisingly, these same samples show only a single structural phase that evolves smoothly. We have recently learned to grow high quality epitaxial films of SrCoO$_{y}$, allowing for more typical single crystal diffraction experiments. Our initial results indicate that magnetic phase separation is suppressed in the films.