Structural, magnetic, and superconducting properties of pulsed-laser-deposition-grown La 1.85 Sr 0.15 CuO 4 / La 2 / 3 Ca 1 / 3 MnO 3 superlattices on (001)-oriented LaSrAlO 4 substratesстатья
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Аннотация:Epitaxial La1.85Sr0.15CuO4/La2/3Ca1/3MnO3 (LSCO/LCMO) superlattices on (001)-oriented LaSrAlO4 substrates
have been grown with pulsed laser deposition technique. Their structural, magnetic, and superconducting
properties have been determined with 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 the large mismatch between the in-plane lattice parameters of LSCO
(a = 0.3779 nm) and LCMO (a = 0.387 nm) these superlattices can be grown epitaxially and with a high
crystalline quality. While the first LSCO layer remains clamped to the LaSrAlO4 substrate, a sizable strain
relaxation occurs already in the first LCMO layer. The following LSCO and LCMO layers adopt a nearly
balanced state in which the tensile and compressive strain effects yield alternating in-plane lattice parameters
with an almost constant average value. No major defects are observed in the LSCO layers, while a significant
number of vertical antiphase boundaries are found in the LCMOlayers. The LSCO layers remain superconducting
with a relatively high superconducting onset temperature of T onset
c
≈ 36 K. The macroscopic superconducting
response is also evident in the magnetization data due to a weak diamagnetic signal below 10 K for H ab and a
sizable paramagnetic shift for H c that can be explained in terms of a vortex-pinning-induced flux compression.
The LCMO layers maintain a strongly ferromagnetic state with a Curie temperature of T Curie ≈ 190 K and a large
low-temperature saturation moment of about 3.5(1) μB per Mn ion. These results suggest that the LSCO/LCMO
superlattices can be used to study the interaction between the antagonistic ferromagnetic and superconducting
orders and, in combination with previous studies on YBa2Cu3O7−x/La2/3Ca1/3MnO3 superlattices, may allow
one to identify the relevant mechanisms.