H–T phase diagram for the giant magnetic flux jumps in low temperature superconductors and high temperature superconductors

Abstract

We have studied magnetothermal instabilities both theoretically and experimentally. Magnetostriction and magnetization hysteresis loops with flux jumps were calculated over a wide range of experimental parameters employing three critical state models: the original Bean model, the Kim–Anderson model, and the exponential model. The influence of the magnetic prehistory on the flux jumps, magnetostriction, and the magnetization was investigated for the LaSrCuO crystal. H–T diagrams of flux instabilities were constructed from calculation and from experimental results. One can see good qualitative agreement between these two diagrams.

Magnetic flux jumps in texturedBi2Sr2CaCu2

“…Therefore for a number of jumps observed at 1.95 K, the magnetization of the sample does not drop to zero, as one can see in Figure 1. The magnetic history dependence on flux jumping, shown in Figure 1, can also be accounted for by the theory presented in references [7,8]. In these references, the temperatures and magnetic field range for which flux jumps occur was studied in the framework of the adiabatic theory, assuming different dependences of the critical current density as a function of the magnetic field.…”

“…The behavior of the magnetization jumps displayed by our Bi 2 Sr 2 CaCu 2 O 8+δ sample and shown in Figure 1, is typical for thermally activated flux jumps in type II superconductors [1,2,3,4,5,7,8,9,10,11,12,13,14]. This data allows one to construct a relation between the field of the first flux jump, B f j1 and temperature, as shown in Figure 4.…”

“…In this case, even if there are no jumps in the virgin magnetization curve, some jumps (so-called "solitary jumps" [7]) may appear after reversal of external magnetic field direction. When the critical current density is a non-monotonic function of the magnetic field (the so-called "fish tail" or "butterfly" effect), then under appropriate conditions so-called "island jumps" may also be found [8]. All these phenomena result from the changes in magnetic field profile in a superconducting sample caused by the field dependence of the critical current density as well as by magnetic history.…”

Avalanche-like vortex penetration driven by pulsed microwave fields in an epitaxial LaSrCuO thin film

“…3,4,15,[20][21][22][23][24][25] 24, 25 The investigation of TMI in HTS is relevant to understand the complexity of the vortex matter in the mixed state of these materials. From the point of view of the applications, flux jumps are problematic as they can drive the superconductors into a normal or resistive state.…”

“…The heat released by the moving vortices leads in turn to further flux motion giving as a consequence a positive feedback process. [2][3][4] The effect of the vortex and temperature redistribution depends on the ratio s of the magnetic flux (t mag ) and thermal (t th ) diffusion time constants: 2 s t mag =t th ¼ l 0 j=Cq f . Here l 0 is the magnetic permeability of vacuum, and j, C, and q f are, respectively, the thermal conductivity, the heat capacity, and the flux flow resistivity of the material.…”