The magnetic field distribution around the vortices in TmNi2B2C in the paramagnetic phase was studied experimentally as well as theoretically. The vortex form factor, measured by small-angle neutron scattering, is found to be field independent up to 0.6 Hc2 followed by a sharp decrease at higher fields. The data are fitted well by solutions to the Eilenberger equations when paramagnetic effects due to the exchange interaction with the localized 4f Tm moments are included. The induced paramagnetic moments around the vortex cores act to maintain the field contrast probed by the form factor.
@article{arxiv.0708.4411,
title = {Pauli Paramagnetic Effects on Vortices in Superconducting TmNi2B2C},
author = {L. DeBeer-Schmitt and M. R. Eskildsen and M. Ichioka and K. Machida and N. Jenkins and C. D. Dewhurst and A. B. Abrahamsen and S. L. Bud'ko and P. C. Canfield},
journal= {arXiv preprint arXiv:0708.4411},
year = {2007}
}