Optimizing magnetic heating of isolated magnetic nanowires (MNWs) by simulation

Abstract

Magnetic properties such as coercivity, remanence and saturation magnetization will determine the area enclosed by the hysteresis loop of a magnetic material, which also represents magnetic heating. Nanowarming of cryopreserved organs is a new application for magnetic heating using nanoparticles. In this paper, isolated Ni MNW of different sizes and shapes are studied via micromagnetic simulation to explore the optimization of heating using individual MNW. Ellipsoidal MNWs with small (30nm) diameters turn out to be most promising in heating ability due to their large hysteresis area and their potential to distribute uniformly in an organ that is being heated. In addition to optimized heating, a special switching pattern of magnetic moment was also observed for cylindrical large (200nm) MNW. This special switching pattern can trigger applications such as quantum computing.

Irreversible and Reversible Switching in Nanomagnet Arrays and Hard Drive Media

“…At Hz=0, Mz also = 0, likely due to completely in-plane moments that form a circle. This has been shown in simulations previously [9]. These moments appear to reversibly cant up or down, with shorter vortices as the diameter is reduced.…”

“…These moments appear to reversibly cant up or down, with shorter vortices as the diameter is reduced. According to the simulations [9], in all but the 200nm diameter MNWs, the remaining irreversible switching is likely to involve a propagating vortex domain wall at Hc, skewed by interactions (similar to the Preisach model once reversible interactions are removed).…”

“…Yet, as mentioned above, artifacts appear in FORC diagrams if the arrays are close-packed such that simulations have been required to explain their FORC diagrams [1][2][3][4][5][6] It is rarely mentioned, but another interesting parameter that can be varied in MNWs is the degree of reversible and irreversible switching. Micromagnetic simulations have recently shown that 'larger' (still nanoscale, eg: 50-200nm) MNWs typically form vortex domain walls at their ends before switching [9,10]. These vortices can extend fairly far down the nanowire before they pull away from the ends and propagate along the nanowire to switch it.…”

Bioapplications of Magnetic Nanowires: Barcodes, Biocomposites, Heaters

“…Optimized spherical nanoparticles, such as superparamagnetic iron oxide nanoparticles (SPIONs), can reach the nanowarming rates of 130 °C/min with 500 Oe (20 kA/m) at 360 kHz and the concentrations of 10 mg/mL. MNWs have recently proven [ 18 ] to be excellent nanowarmers [see Fig. 5(b) ], with the nanowarming rates of 400 °C/min with 1 mg MNW/mL CPA and 1000 °C/min with 5 mg/mL.…”

“…Free-floating MNWs in suspensions or assays will be internalized by cells [ 14 ], [ 15 ] which then dispense exosomes [ 16 ], both of which can be subsequently collected with an external magnet [ 17 ] or read-out by similar methods as used for MNWs in membranes [ 12 ]. A very recent application of MNWs is nanowarming of cryopreserved tissues and organs, which enables the freezing of biological time [ 18 ]. Bioapplications of MNWs are wide-ranging and cannot be covered well in this article alone.…”