[en] We present superconducting properties and vortex states in a thick amorphous Mg_xB_1-x film with x=0.31. Measurements of dc and ac complex resistivities in the mixed state reveal the presence of the vortex-glass transition in three dimensions. Based on the data, we construct the vortex phase diagram in the field-temperature plane. We find that there is the relatively large vortex-liquid phase, which persists down to low temperatures

[en] The superconducting properties in thick amorphous Mg_xB_1-x films with different x (∼0.3-0.4) are presented. The transition temperature T_c changes smoothly as a function of x, exhibiting a peak (T_c=6.1 K) at x∼0.33. This fact, together with the finding that the resistive transition in zero field is sufficiently sharp, demonstrates that our films are highly amorphous and electronic states change systematically as a function of x. On the basis of the ac-complex-resistivity for selected fields, the vortex-solid state is suggested to be the vortex glass

[en] We measure the ac complex resistivity in the mixed state of amorphous Mo_xSi_1-x films with different thicknesses (t). For films with t=100 and 30 nm we can determine the vortex-glass-transition (VGT) line which persists down to low temperatures (T) up to high fields (B) near the upper critical field at T=0. In the liquid phase the vortex-relaxation time (τ_g) extracted from the frequency dependence of ac resistivity follows the power-law T dependence expected by the VG theory for three dimensions (3D). For the thinner (10, 6 nm) films, both the dc resistivity and τ_g follow the activated T dependence except for the very low-T region, suggestive of 2D VGT. For all of the films studied, τ_g in high B shows a decreased T dependence at lower T, indicating the quantum-driven fluctuations

[en] We present measurements of dc and ac complex resistivities for amorphous Mo_xSi_1-x films with different disorder and dimensionality (film thickness t). For thicker films with t=100 and 30 nm we determine the vortex-glass-transition (VGT) line B_g(T) which persists down to low enough temperatures T up to high fields B near B_c2(0), where B_c2(0) is an upper critical field at T=0. The finite quantum-vortex-liquid (QVL) phase at T=0, B_g(0)< B< B_c2(0), is observed for these films. We find a trend for the QVL phase to increase as the film becomes more resistive and/or thinner. This result is consistent with a view that the QVL phase is driven by strong quantum fluctuations, which are enhanced with increasing disorder and with decreasing dimensionality. For the thinnest film with t=6 nm, both the dc resistivity and vortex relaxation time follow the activated T dependence, suggestive of two-dimensional VGT