Structural, magnetic and superconducting properties of pulsed-laser-deposition-grown $ m{La_{1.85}Sr_{0.15}CuO_{4}/La_{2/3}Ca_{1/3}MnO_{3}}$ superlattices on $ m{(001)}$-oriented $ m{LaSrAlO_{4}}$ substrates

摘要

Epitaxial La1.85Sr0.15CuO4/La2/3Ca1/3MnO3 superlattices on (001)-orientedLaSrAlO4 substrates have been grown with pulsed laser deposition technique.Their structural, magnetic and superconducting properties have been determinedwith in-situ reflection high energy electron diffraction, x-ray diffraction,specular neutron reflectometry, scanning transmission electron microscopy,electric transport, and magnetization measurements. We find that despite thelarge mismatch between the in-plane lattice parameters of LSCO and LCMO thesesuperlattices can be grown epitaxially and with a high crystalline quality.While the first LSCO layer remains clamped to the LSAO substrate, a sizeablestrain relaxation occurs already in the first LCMO layer. The following LSCOand LCMO layers adopt a nearly balanced state in which the tensile andcompressive strain effects yield alternating in-plane lattice parameters withan almost constant average value. No major defects are observed in the LSCOlayers, while a significant number of vertical antiphase boundaries are foundin the LCMO layers. The LSCO layers remain superconducting with a relativelyhigh superconducting onset temperature of about 36 K. The macroscopicsuperconducting response is also evident in the magnetization data due to aweak diamagnetic signal below 10 K for H || ab and a sizeable paramagneticshift for H || c that can be explained in terms of a vortex-pinning-inducedflux compression. The LCMO layers maintain a strongly ferromagnetic state witha Curie temperature of about 190 K and a large low-temperature saturationmoment of about 3.5(1) muB. These results suggest that the LSCO/LCMOsuperlattices can be used to study the interaction between the antagonisticferromagnetic and superconducting orders and, in combination with previousstudies on YBCO/LCMO superlattices, may allow one to identify the relevantmechanisms.