Friday, May 3, 2013

1305.0494 (C. Rastovski et al.)

Vortex Lattice Jamming and Metastability Studies by Small Angle Neutron

C. Rastovski, K. J. Schlesinger, W. J. Gannon, C. D. Dewhurst, L. DeBeer-Schmitt, N. D. Zhigadlo, J. Karpinski, M. R. Eskildsen
Recently extensive vortex lattice metastability was reported in MgB2 in connection with a second order rotational phase transition. However, the mechanism responsible for these well-ordered metastable vortex lattice phases is not well understood. Using small-angle neutron scattering, we studied the vortex lattice in MgB2 as it was driven from a metastable to the ground state through a series of small changes in the applied magnetic field. Our results show that metastability in MgB2 is not the result of pinning defects. Rather, we propose that it is due to the jamming of counter rotated vortex lattice domains which prevents a rotation to the ground state orientation. Although granular jamming has been applied to the motion of individual vortices, this is the first experimental evidence that vortex lattice domains can act as granular entities.
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