We use a scanning nanometer-scale superconducting quantum interference device to map the stray magnetic field produced by individual ferromagnetic nanotubes (FNTs) as a function of applied magnetic field. The images are taken as each FNT is led through magnetic reversal and are compared with micromagnetic simulations, which correspond to specific magnetization configurations. In magnetic fields applied perpendicular to the FNT long axis, their magnetization appears to reverse through vortex states, i.e.\ configurations with vortex end domains or -- in the case of a sufficiently short FNT -- with a single global vortex. Geometrical imperfections in the samples and the resulting distortion of idealized mangetization configurations influence the measured stray-field patterns.
@article{arxiv.1709.09652,
title = {Imaging stray magnetic field of individual ferromagnetic nanotubes},
author = {D. Vasyukov and L. Ceccarelli and M. Wyss and B. Gross and A. Schwarb and A. Mehlin and N. Rossi and G. Tütüncüoglu and F. Heimbach and R. R. Zamani and A. Kovács and A. Fontcuberta i Morral and D. Grundler and M. Poggio},
journal= {arXiv preprint arXiv:1709.09652},
year = {2018}
}