The third harmonic components of the ac susceptibility of MgB2 bulk samples have been measured as a function of applied magnetic fields, together with standard magnetization cycles. The irreversibility line (IL) of the magnetic field has been extracted from the onset of the third harmonic components. Using a (1 - t)a glass/liquid best fit where α = 1.27 IL shows a coherent length ξ divergence with exponent v = 0.63, which indicates a 3D behaviour. Moreover, using the numerical solution of the non-linear magnetic diffusion equation, considering the creep model in a 3D vortex glass, a good description of the vortex dynamics has been obtained. The behaviour of the magnetization amplitude (∼Hz) and the ac susceptibility signals (kHz), at different applied magnetic fields, 3.5 T < Hdc < 4.5 T, and at the reduced temperature 0.86 < t < 0.93 (T = 22 K), shows that the superconducting dynamic response of vortices in the MgB2 samples is not evidently dependent on the frequency.
All Science Journal Classification (ASJC) codes
- Ceramics and Composites
- Condensed Matter Physics
- Metals and Alloys
- Materials Chemistry
- Electrical and Electronic Engineering
Di Gioacchino, D., Gambardella, U., Tripodi, P., & Grimaldi, G. (2003). Irreversibility line and magnetic field dependence of the critical current in superconducting MgB. Superconductor Science and Technology, 16(4), 534 - 537. https://doi.org/10.1088/0953-2048/16/4/319