Abstract
The superconductor TmNiBC possesses a significant fourfold basal plane anisotropy, leading to a square vortex lattice (VL) at intermediate fields. However, unlike other members of the borocarbide superconductors, the anisotropy in TmNiBC appears to decrease with increasing field, evident by a reentrance of the square VL phase. We have used small-angle neutron scattering measurements of the VL to study the field dependence of the anisotropy. Our results provide a direct, quantitative measurement of the decreasing anisotropy. We attribute this reduction of the basal plane anisotropy to the strong Pauli paramagnetic effects observed in TmNiBC and the resulting expansion of vortex cores near .
- Received 11 August 2012
DOI:https://doi.org/10.1103/PhysRevB.86.144501
©2012 American Physical Society