Magnetism and superconductivity of Fe/Nb/Fe trilayers

Th. Mühge; K. Westerholt; H. Zabel; N. N. Garif'yanov; Yu. V. Goryunov; I. A. Garifullin; G. G. Khaliullin

doi:10.1103/PhysRevB.55.8945

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Magnetism and superconductivity of Fe/Nb/Fe trilayers

Th. Mühge, K. Westerholt, H. Zabel, N. N. Garif'yanov, Yu. V. Goryunov, I. A. Garifullin, G. G. Khaliullin

DOI 10.1103/PhysRevB.55.8945 · Physical Review B

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Abstract

Sputtered Fe/Nb/Fe trilayers were prepared with Nb thicknesses dNb in the range 300–800 Å and with Fe thicknesses dFe in the range 0–30 Å. X-ray reflectivity measurements revealed the high quality of the film structure with low surface and interface roughnesses. Magnetic properties of the samples were studied using the magneto-optical Kerr effect, ferromagnetic-resonance and magnetization measurements by a SQUID magnetometer. For constant dFe a decrease of Tc with decreasing dNb was observed up to a critical thickness dNbcrit below which superconductivity vanishes. We derived dNbcrit≈320 Å independent of dFe for dFe⩾7 Å. The temperature dependence of the upper critical field Hc2(T) showed two- and three-dimensional features for parallel and perpendicular orientations of the magnetic field, respectively. At the Nb/Fe interface in the trilayer systems an Fe-rich interlayer with nonmagnetic Fe is formed with a thickness depending sensitively on the preparation conditions. We observed a nonmonotonic dependence of the superconducting transition temperature Tc with increasing dFe and a definite maximum in Tc(dFe) at the onset of ferromagnetic order within the Fe layers. This maximum is attributed to a modification of the repulsive interaction between the electrons in the magnetically 'dead' Fe-rich interlayer when an exchange field in the Fe layer is present.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
Nb Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	7	Pressure not reported	unknown
Nb Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	8	Pressure not reported	unknown