Effect of the variation rate of an external magnetic field on the high-frequency response of surface superconductivity i
- PDF / 445,498 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 78 Downloads / 171 Views
DISORDER, AND PHASE TRANSITION IN CONDENSED SYSTEM
Effect of the Variation Rate of an External Magnetic Field on the High-Frequency Response of Surface Superconductivity in a Critical State V. A. Berezin* and V. A. Tulin** Institute of Microelectronics Technology and High-Purity Materials, Russian Academy of Sciences, Chernogolovka, Moscow oblast, 142432 Russia *e-mail: [email protected] **e-mail: [email protected] Received May 24, 2016; in final form, June 9, 2017
Abstract—The effect of the magnetic field variation rate on the high-frequency absorption of surface superconductivity of cylindrical samples has been studied. It has been shown that the magnitude of additional highfrequency absorption attributed to Kulik vortices does not demonstrate saturation and other critical changes up to a magnetic field variation rate of 350 kOe/s, which indicates that the velocity of motion of Kulik vortices is higher than that of Abrikosov vortices. The effect of the normal core of the sample on the dynamics of a magnetic flux has been discussed. DOI: 10.1134/S1063776117110036
In superconducting materials with a small Ginzburg–Landau parameter κ = ξ/λ, where ξ and λ are the coherence length and the London magnetic field penetration depth, respectively, which exceeds 0.417, in a magnetic field higher than the critical value for the bulk (the thermodynamic critical field Hc for type I superconductors and the second critical field Hc2 for type II superconductors), a thin superconducting layer with a thickness on the order of the coherence length ξ remains on the surface. In a magnetic field parallel to the surface of the superconducting sample, this layer holds up to a field of Hc3 = 1.695Hc2 [1]. For a cylindrical sample in a magnetic field parallel to its axis, a closed superconducting shell similar to a thin-walled superconducting tube is formed. In the 1960s and 1970s, the behavior of superconducting samples in magnetic fields Hc2 < H < Hc3 was studied extensively both theoretically and experimentally [2]. Experimental studies showed that macroscopic samples exhibit a metastable state with a stable superconducting current (with a nonzero magnetic moment) in the range Hc2 < H < Hc3, which exists for a time long enough to introduce the concept of critical current. The critical current of surface superconductivity and the related critical state were studied in [3–6]. Many physical properties of this object are studied in a slowly varying magnetic field in the range Hc2 < H < Hc3. In this case, the surface shell is forced to be in the critical state; i.e., the properties of the shell in the critical state are investigated. If measurements are per-
formed in a static magnetic field without taking certain measures, the properties of the shell depend on the magnetic prehistory. Indeed, the variation of the properties associated with the existence of the critical state are small as compared to full-scale variations in the range Hc2 < H < Hc3. However, under certain conditions, these variations are clearly observed and are associated with
Data Loading...
