Abstract
We report scanning Hall probe imaging of in the superconducting, antiferromagnetic, and weakly ferromagnetic regimes in magnetic fields up to 20 Oe, well below , with two results. First, imaging isolated vortices shows that they spontaneously rearrange on cooling through the antiferromagnetic transition temperature to pin on twin boundaries, forming a striped pattern. Second, a weak, random magnetic signal appears in the ferromagnetic phase below , and no spontaneous vortex lattice is present down to . We conclude that ferromagnetism coexists with superconductivity either by forming small ferromagnetic domains or with oscillatory variation of the magnetization on sub-penetration-depth length scales.
- Received 2 July 2005
DOI:https://doi.org/10.1103/PhysRevB.73.014514
©2006 American Physical Society