Superconducting mesa-structures with a spin filtering manganite interlayer

Kotel’nikov Institute of Radio Engineering and Electronics RAS, Moscow, Russia

^* Corresponding author: karen@hitech.cplire.ru

Published online: 4 July 2018

Abstract

We report on current transport and magnetism in hybrid superconducting mesa-structures prepared from epitaxial superconductor YBa₂Cu₃O_7-δ and manganite LaMnO₃ thin films. Superconducting Au-Nb bilayer was the top electrode. Measurements of magnetic resonance in heterostructure with the only Au top electrode (without Nb) showed ferromagnetic state close to Curie temperature of LaMnO₃, 150 K. A spin filtering was revealed by measurements of tunneling magneto-resistance. Mesa-structures had no superconducting current even at reduced temperature T=300 mK and the smallest manganite interlayer thickness, d_M=5.6 nm. Varying the external magnetic field |H|<10 Oe and dc bias current |I|<0.5 mA the microwave generation with power P <1 pW with a line-width of order 50 MHz was observed in GHz frequency band. The frequency of generation could be tuned by the biasing current with a rate 10¹³ Hz/A. The impact of spin polarized current on microwave generation is discussed taking into account the asymmetry of oscillation amplitudes over the applied magnetic field.