Effect of spin injection from colossal magnetoresistance material into superconducting thin film of YBa 2 Cu 3 O 7- T.B. Hjelmeland Department of Physics, University of Oslo, P.O.Box 1048, Blindern, 0316 Oslo, Norway t.b.hjelmeland@fys.uio.no Y. Volkov Kiev-Pechersk Lyceum 171 Leipzig street 11A, 01015 Kiev, Ukraine veg2001@gmail.com P. Mikheenko* Department of Physics, University of Oslo, P.O.Box 1048, Blindern, 0316 Oslo, Norway *pavlo.mikheenko@fys.uio.no Abstract— By specific design of the sample, in which SrTiO3 substrate is fully covered by a thin film of the colossal magnetoresistive material La0.67Ca0.33MnO3 (LCMO) and the latter is partially covered by high-temperature superconductor YBa2Cu3O7- (YBCO), and by using multiple current and voltage contacts, direct evidence of spin injection from LCMO to YBCO is obtained. It is found that spin-polarized electrons injected from LCMO strongly influence not only superconducting, but also normal state of YBCO. The effect of deposition conditions of LCMO and YBCO and the quality of the interface on the spin injection efficiency is clarified. A surprising peak in the temperature dependence of resistance seen on ex-situ sample is explained as combination of two effects: strong influence of spin- polarized electrons on superconductor just below its critical temperature and the interface-controlled shift of Curie temperature of LCMO to low temperatures. Considering expected use of LCMO and YBCO in composite quantum computation circuits, a possibility of their combination with another advanced quantum material, graphene, is explored. Keywords—high temperature superconductor; colossal magnetoresistance material; spin injection; nano-magnetism; graphene. I. INTRODUCTION With advance of superconducting quantum computing [1], there is renewed interest to higher-temperature superconductors in combination with spin-polarized materials [2], which is stimulated by the attempts to confine quantum processing on nanometer scale making computers more compact, and extend their operation to higher temperatures [3]. Graphene [4] is another important material that demonstrates quantum behaviour even at room temperature. Merging spin-polarized materials, superconductors and graphene would lead to novel quantum devices with enhanced performance and functionality. Two particular materials: spin-polarized La0.67Ca0.33MnO3 (LCMO) and high-temperature superconductor YBa2Cu3O7- (YBCO) are of special interest [5,6], as they have similar crystal lattice and can be prepared epitaxially on top of each other. There are multiple investigations of these compounds and their effect on each other, see, for example [5-8]. However, simple experiments showing where their interaction is strongest are needed and combinations of these materials with graphene should be explored. LCMO and YBCO are delicate compounds. Small changes in their chemical composition, especially oxygen content, presence of impurities or diffusion of elements through interface, when they are prepared together, can produce unexpected effects, like appearance of stripy magnetic structure and resistance peak below critical temperature of superconductor [9]. In this paper, using specific design of LCMO/YBCO bilayer, we clarify nature of the resistance peak, demonstrate effect of spin injection on superconducting and normal state of YBCO and explore possibility of combining LCMO and YBCO with graphene. II. EXPERIMENTAL A bilayer thin-film structure containing LCMO and YBCO was epitaxially grown by pulsed laser deposition on SrTiO3 (STO) substrate. First, the 5x10-mm 2 substrate was fully covered by a 100-nm thick layer of LCMO. After that, using