  We present experimental evidence of metastable magnetic domains in
cylindrical CoNi nanowires. Transverse (perpendicular) domains have been
previously observed only in flat nanostrips. Here they are found together with
more conventional vortex domains along the same cylindrical nanowire, denoting
a bistable system with similar free energies. The surface and the inner
magnetization distribution in both types of domains are analyzed by
Photo-Emission Electron Microscopy (PEEM) with X-ray magnetic circular
dichroism (XMCD) contrast, and hysteresis loop in individual nanowires are
measured by Magneto-optical Kerr effect. These experimental data are understood
and compared with complementary micromagnetic simulations. The transverse
domain states are potentially more important for sensing and recording
applications than commonly observed vortex domains since they create larger
surface stray fields.
