• Keimer, Bernhard

Abstract

<jats:p>We have investigated the structural, magnetic and superconduction properties of [Nb(1.5 nm)/Fe(<jats:italic>x</jats:italic>)]<jats:sub>10</jats:sub> superlattices deposited on a thick Nb(50 nm) layer. Our investigation showed that the Nb(50 nm) layer grows epitaxially at 800 °C on the Al<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub>(1−102) substrate. Samples grown at this condition possess a high residual resistivity ratio of 15–20. By using neutron reflectometry we show that Fe/Nb superlattices with <jats:italic>x &lt;</jats:italic> 4 nm form a depth-modulated FeNb alloy with concentration of iron varying between 60% and 90%. This alloy has weak ferromagnetic properties. The proximity of this weak ferromagnetic layer to a thick superconductor leads to an intermediate phase that is characterized by a suppressed but still finite resistance of structure in a temperature interval of about 1 K below the superconducting transition of thick Nb. By increasing the thickness of the Fe layer to <jats:italic>x</jats:italic> = 4 nm the intermediate phase disappears. We attribute the intermediate state to proximity induced non-homogeneous superconductivity in the structure.</jats:p>

Topics

• impedance spectroscopy
• resistivity
• phase
• iron
• superconductivity
• superconductivity
• reflectometry