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We present the modulation of anisotropy field, coercivity, and domain wall (DW) velocity in CoFeB/MgO thin films with perpendicular anisotropy by applying voltages across an ionic liquid gate. Domain wall velocities in the creep regime can be modulated by a factor of 4.2, and the anisotropy field of the device can be modulated by 40 mT when going from +0.8V to -0.8V. The applied E-fields are seen to significantly influence DWs' pinning, depinning, and nucleation processes. In addition, we report on the evolution of the magnetic properties of the liquid/solid device as a function of time going from the pristine CoFeB/MgO film through device fabrication and operation up to one month. These results show that the solid/liquid device structure based on CoFeB/MgO thin films can be an efficient way to control magnetic properties with voltages below 1V. [ABSTRACT FROM AUTHOR]

Metal electrodeposits reflect the pattern of magnetic field created at the cathode by a magnet array. The effect is explained by magnetic pressure, which modifies the thickness of the cation diffusion layer governing mass transport. An inverse effect, when a strongly paramagnetic but non-electroactive cation, such as Dy3+ is present in the electrolyte, is related to inhibition of convection of water liberated at the cathode by the magnetic field gradient. Magnetic structuring depends on the relative susceptibility of the electroactive species and the non-electroactive background. [ABSTRACT FROM AUTHOR]

The study of exogenous and endogenous nanoscale magnetic material in biology is important for developing biomedical nanotechnology as well as for understanding fundamental biological processes such as iron metabolism and biomineralization. Here, we exploit the magneto-optical Faraday effect to probe intracellular magnetic properties and perform magnetic imaging, revealing the location-specific magnetization dynamics of exogenous magnetic nanoparticles within cells. The opportunities enabled by this method are shown in the context of magnetic hyperthermia; an effect where local heating is generated in magnetic nanoparticles exposed to high-frequency AC magnetic fields. Magnetic hyperthermia has the potential to be used as a cellular-level thermotherapy for cancer, as well as for other biomedical applications that target heat-sensitive cellular function. However, previous experiments have suggested that the cellular environment modifies the magnetization dynamics of nanoparticles, thus dramatically altering their heating efficiency. By combining magneto-optical and fluorescence measurements, we demonstrate a form of biological microscopy that we used here to study the magnetization dynamics of nanoparticles in situ , in both histological samples and living cancer cells. Correlative magnetic and fluorescence imaging identified aggregated magnetic nanoparticles colocalized with cellular lysosomes. Nanoparticles aggregated within these lysosomes displayed reduced AC magnetic coercivity compared to the same particles measured in an aqueous suspension or aggregated in other areas of the cells. Such measurements reveal the power of this approach, enabling investigations of how cellular location, nanoparticle aggregation, and interparticle magnetic interactions affect the magnetization dynamics and consequently the heating response of nanoparticles in the biological milieu.

The channeling of spin waves with domain walls in ultrathin ferromagnetic films is demonstrated theoretically and through micromagnetics simulations. It is shown that propagating excitations localized to the wall, which appear in the frequency gap of bulk spin wave modes, can be guided in curved geometries and propagate in close proximity to other channels. For Néel-type walls arising from a Dzyaloshinskii-Moriya interaction, the channeling is strongly nonreciprocal and group velocities can exceed 1  km/s in the long wavelength limit for certain propagation directions. The channeled modes represent an unusual analogy of whispering gallery waves that are one dimensional and nonreciprocal with this interaction. Moreover, a sufficiently strong Dzyaloshinskii-Moriya interaction can create a degeneracy of channeled and propagating modes at a critical wave vector.