Magnetoelastic Coupling in the Perovskite-type Co Oxides Sr1-xYxCoO3-δ

We performed thermal expansion and magnetostriction measurements of the perovskite-type Co oxides Sr1-xYx-CoO3-delta and Ca-doped Sr1-yY0.22CayCoO3-delta in high magnetic fields. Our experimental results show decrease of the magnetization of Sr(1-xY)xCoO(3-delta) upon cooling in the magnetic ordered phase, accompanied by considerable shrinkage of the crystal lattice. On the contrary, the application of magnetic fields causes the expansion of the lattice volume, resulting in positive magnetstriction. The strong relation between the ferromagnetic moment and the crystal lattice, suggested by our measurements, is consistent with the occurrence of a spin crossover in the magnetic ordered phase of these compounds.