Transport properties of YBa2Cu3Ox /La0.67Sr0.33MnO3 nanostrips and YBa2Cu3Ox/La0.67Sr0.33MnO3/YBa2Cu3Ox nanojunctions

Abstract

A metallic ferromagnet (F) in proximity with a superconductor (S) can transport supercurrent on a long distance through conversion of opposite-spin singlet Cooper pairs (CP) into equal-spin triplet CP (long range triplet component, LRTC), which are not broken by the exchange energy of F. The optimal conditions for the conversion are yet to be clarified; however, it is accepted that the key point to this process include high interface transparency and magnetic inhomogeneity at the SF interface. The aim of our paper is to study SF nanostrips (length of about 1500 nm and width down to 300 nm) and lateral SFS nanojunctions based on high critical temperature YBa2Cu3Ox (YBCO) and half-metallic La0.67Sr0.33MnO3 (LSMO) thin films. We applied a focused Ga+ ion beam (FIB) for patterning the SF nanostrips, as well as lateral SFS nanojunctions, by creating a slot in the nanostrip after removing the YBCO film in the slot along a length of about 200 nm. The temperature dependences of the samples resistance R(T) show critical temperature TCn ≈ 89 K of the SF nanostrips; however, the SFS nanojunctions at T < TCn show a residual resistance R < 100 Ω corresponding to a dirty LSMO (ρ≈ 10 mΩ cm) in the slot. The LRTC was not observed in our lateral SFS nanojunctions until now.