Reversal mechanisms in cylindrical magnetic nanowires

Magnetic nanowires (MNWs) can be engineered using composition and shape, and by modulating both
of these along the axes of the MNWs. Here, magnetic structure and reversal will be discussed, using
theoretical analysis and experimental measurements of both single MNWs and arrays of vertically
aligned MNWs. Diameter has been used to control the coercivity of MNWs because the reversal occurs
via coherent rotation for small diameters but switches to vortex walls for large diameters. This
simplified explanation roughly covers the experimental results from hysteresis loops and first order
reversal curves (FORC), but the actual magnetic structure is recently understood to contain more
complex structures [1]. Simulations indicate that single MNWs have magnetic features that are not seen
when even a few nanowires are allowed to interact. This picture can become more complicated when
the MNWs are modulated along their length. Electron holograph [2], X-rays [3,4], and neutrons [5] have
enabled experimental visualization the magnetization deep inside single MNWs, modulated MNWs, and
arrays. These together with new FORC techniques, and standard measurements, eg:
magnetoresistance, are important for determining inherent reversal mechanisms and how they are
impacted by interactions between the MNWs in close-packed arrays.

[1] Magnetic Nano- and Microwires 2 (2020) Elsevier; [2] J. Mater. Chem C (2017) 7546; [3] ACS Nano
(2020) 12819; [4] J. Phys. D (2016) 363001; [5] ACS Nano (2017) 8311