High-Frequency Magnetic Response of Arrays of Planar Fe65Co35 Nanodots: Effects of Bias Field and Thermal Fluctuations

Using temperature-dependent micromagnetic simulations, we analyze the magnetic response of arrays of nanoscale disk-shaped particles to linear or rotating fields of sub-GHz and GHz frequency with relevance to designing novel core materials for the on-chip power conversion. The nanodot arrays consist of Fe65Co35 disks of 5 nm (12 nm) diameter and 1 nm (2.4 nm) height arranged in columns that occupy sites of a hexagonal lattice. The volume of smaller (bigger) nanodots corresponds to the low-energy-barrier (high-energy-barrier) regime for thermal excitations at room temperature. A way to increase the amplitude of the response function and stabilize its phase (in order to reduce the residual loss) is to apply a static bias field perpendicular to the driving field. This situation is analyzed numerically for two cases of structure preparation in terms of the crystalline anisotropy in which the uniaxial anisotropy directions of single nanodots are either randomly or uniformly oriented. We predict that the strength of the dynamical response (the susceptibility
$\chi $
) is comparable to our previously studied (Brzuszek et al., 2023) systems of spherical magnetic nanoparticles (MNPs) of 5 nm diameter (
$1.0 < \chi < 2.5$
at 0.1 GHz) in spite of the lowered volumetric ratio of the magnetic subsystem
$x$
(
$x\ge 0.13$
for MNP arrays versus
$x=0.07$
for magnetic nanodot (MND) arrays), based on ferromagnetic resonance.