Superconductivity and Ferromagnetism in La0.67Sr0.33MnO3//YBa2Cu3O7La_{0.67}Sr_{0.33}MnO_3//YBa_2Cu_3O_7 Nanosized Heterostructures

In this work we present recent experimental studies of heterostructures composed of ferromagnetic $La_{0.67}Sr_{0.33}MnO_3$ (LSMO) and superconducting $YBa_2Cu_3O_7$ (YBCO) multilayers grown by dc sputtering method. The transport and magnetic properties of the large set of heterostructures were investigated in a wide temperature range from 2 to 400 K and in fields up to 12.5 T. The resistivity and the upper critical field were measured for samples with the plane active dimensions 1.5× 5 mm². The Nernst effect was studied in the mixed state revealing the characteristic temperature dependence of the Nernst signal which was correlated with variation of the upper critical field. We have observed an influence of the magnetic LSMO layer on the superconducting properties of the adjacent YBCO layer which consists in a substantial reduction of the superconducting critical temperature and a small lowering of the upper critical field