Using Magnetic Nanoparticles to Improve Flux Pinning in YBa2Cu3Ox Films

Superconductors application can lead to significant economic benefits, especially in combination with use of liquid hydrogen, which is becoming an important part of the renewable energy economy. While many traditional superconductors cannot operate in liquid hydrogen, new materials, like high-temperature superconductors and MgB2 perfectly suit this purpose. YBa
2
Cu
3
O
x
is one of the most used high-temperature superconductors. It can operate even in liquid nitrogen, at the temperature of 77.3 K, but has a strong advantage of enhanced critical current density at the boiling temperature of liquid hydrogen of 20 K. A disadvantage of this material is the absence of natural c-axis pinning centers defining its critical current density. A usual way to solve this problem is the introduction of artificial pinning centers in the form of nanoparticles. The nanoparticles, however, reduce the volume of the superconductor and can lead to the formation of high-angle grain boundaries detrimental for the critical current. Here we explore an approach of depositing magnetic nanoparticles on the surface of superconducting films, which neither reduce the volume of the superconductor nor create high-angle grain boundaries. The additional pinning by these nanoparticles is studied by recording magneto-optical images of the films.