Superconductor-ferromagnet-superconductor nanojunctions from perovskite materials

The lateral superconductor-ferromagnet-superconductor (SFS) nanojunctions based on high critical temperature superconductor YBa2Cu3Ox (YBCO) and half-metallic ferromagnet La0.67Sr0.33MnO3 (LSMO) thin films were prepared to investigate a possible presence of long range triplet component (LRTC) of Cooper pairs in the LSMO. We applied Ga3+ focused ion beam patterning to create YBCO/LSMO/YBCO lateral type nanojunctions with LSMO length as small as 40 nm. The resistivity vs. temperature, critical current density vs. temperature and resistance vs. magnetic field dependence were studied to recognize the LRTC of Cooper pairs in the LSMO. A non-monotonic temperature dependence of junction critical current density and a decrease of the SFS nanojunction resistance in increased magnetic field were observed. Only weak manifestations of LRTC and some qualitative agreement with theory were found out in SFS nanojunctions realized from the perovskite materials. The presence of equal-spin triplet component of Cooper pairs in half-metallic LSMO ferromagnet is not such apparent as in SFS junctions prepared from low temperature superconductors NbTiN and half-metallic ferromagnet CrO2.