Origin of magnetic flux-jumps in Nb films subject to mechanical vibrations and corresponding magnetic perturbations

In this paper the origin of flux-jumps in Nb thin films is established during magnetization measurements using a vibrating sample magnetometer (VSM). Magnetization measurements of the flux avalanche activity show its strong dependence on frequency and amplitude of VSM vibration. In particular, under certain conditions the vibrations induce a transition from a stable superconducting critical state to an undercritical state, accompanied by the 20-fold drop in the magnetic moment. These features allow the elucidation of the origin of the flux-jumps. In contrast to the commonly assumed thermomagnetic instabilities to be responsible for the flux-jumps in Nb films, our results provide solid support for an alternative explanation being due to criticalitybuilt instability well represented by a sandpile. Considering properties of the flux-flow during a flux avalanche regime allows us to estimate nonuniformity of a magnetic field in a VSM sample space developed as a result of vibrations. Disciplines Engineering | Physical Sciences and Mathematics Publication Details Golovchanskiy, I. A., Pan, A. V., Johansen, T. H., George, J., Rudnev, I. A., Rozenfeld, A. & Fedoseev, S. A. (2018). Origin of magnetic flux-jumps in Nb films subject to mechanical vibrations and corresponding magnetic perturbations. Physical Review B: Covering condensed matter and materials physics, 97 (1), 014524-1-014524-7. Authors Igor A. Golovchanskiy, Alexey V. Pan, Tom H. Johansen, Jonathan George, Igor Rudnev, Anatoly B. Rosenfeld, and Sergey Fedoseev This journal article is available at Research Online: http://ro.uow.edu.au/aiimpapers/2932 PHYSICAL REVIEW B 97, 014524 (2018) Origin of magnetic flux-jumps in Nb films subject to mechanical vibrations and corresponding magnetic perturbations Igor A. Golovchanskiy,1,2,3 Alexey V. Pan,1,4,* Tom H. Johansen,1,5 Jonathan George,1 Igor A. Rudnev,4 Anatoly Rosenfeld,6 and Sergey A. Fedoseev1,6 1Institute for Superconducting and Electronic Materials, University of Wollongong, Northfields Avenue, Wollongong, New South Wales 2522, Australia 2Moscow Institute of Physics and Technology, State University, 9 Institutskiy pereulok, Dolgoprudny, Moscow Region 141700, Russian Federation 3National University of Science and Technology (MISIS), 4 Leninsky prospekt, Moscow 119049, Russian Federation 4National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), 31 Kashirskoye Shosse, 115409 Moscow, Russian Federation 5Department of Physics, University of Oslo, Blindern, N-0316 Oslo, Norway 6Centre for Medical Radiation Physics, University of Wollongong, Northfields Avenue, Wollongong, New South Wales 2522, Australia (Received 13 November 2017; published 25 January 2018) In this paper the origin of flux-jumps in Nb thin films is established during magnetization measurements using a vibrating sample magnetometer (VSM). Magnetization measurements of the flux avalanche activity show its strong dependence on frequency and amplitude of VSM vibration. In particular, under certain conditions the vibrations induce a transition from a stable superconducting critical state to an undercritical state, accompanied by the 20-fold drop in the magnetic moment. These features allow the elucidation of the origin of the flux-jumps. In contrast to the commonly assumed thermomagnetic instabilities to be responsible for the flux-jumps in Nb films, our results provide solid support for an alternative explanation being due to criticality-built instability well represented by a sandpile. Considering properties of the flux-flow during a flux avalanche regime allows us to estimate nonuniformity of a magnetic field in a VSM sample space developed as a result of vibrations. DOI: 10.1103/PhysRevB.97.014524