Thermally activated flux creep in nanocrystalline δ-MoN thin films

Abstract

We study the vortex dynamics in a nanocrystalline 420 nm thick δ-MoN film on Si (100). The film was grown at room temperature by reactive sputtering and following it is crystallized by thermal annealing at 973 K for one hour. The microstructure shows grains with sizes between 30 nm and 65 nm. The film displays a Tc of 11.2 K. The magnetic field dependence of the critical current density Jc at intermediate and low fields (related to the upper critical field) displays a power-law regime. The self-field Jc at 4.5 K is ≈2 MA cm−2. The pinning force Fp exhibits a maximum at h ≈ 0.3, which is in agreement with vortex pinning produced by grain boundaries. An Anderson-Kim mechanism describes the temperature dependence of the flux creep rates. The U0 values range from ≈2500 K for μ0H = 0.02 T to ≈1300 K for μ0H = 0.5 T.