Investigation of Properties of Nanostructured MgB₂ Films Deposited by Magnetron Sputtering

Abstract

The paper presents the results of studying the structure, phase composition, relieph, and superconducting characteristics of oxygen-containing thin films of magnesium diboride (MgB ₂ )deposited on a dielectric substrate by magnetron sputtering of diboride-magnesium targets. The possibility of forming films of varying degrees of crystalline perfection and phase composition in the process of precipitation and annealing is shown, depending on the conditions of deposition and annealing. In the films, it is possible to realize various combinations of the Abrikosov vortex pinning centers (in the places of fluctuations of the critical temperature of the superconducting transition (T _c -type)and in the places of fluctuations in the mean free path (I-type)), whose origin and density are influenced by the conditions for the synthesis of films. It is shown that the deposited films consist of a superconducting matrix, which is a solid solution of oxygen in a lattice of magnesium diboride of the MgB _x O _y type; the density of the superconducting critical current of the films can reach 1.8 × 10 ¹¹ -8.2 × 10 ¹⁰ A/m ² at 10 K and 8 × 10 ¹⁰ -2.8 × 10 ¹⁰ A/m ² at 20 K in fields of 0-1 T (when the external magnetic field is oriented perpendicular to the plane of the substrate).