Micromagnetic Simulation in 1-D Chain of Nanosized Thin Truncated Conical Disks

Angular dependence of coercivity and remanence in 1-D chain of soft permalloy thin truncated conical disks of height 20 nm has been investigated by using finite-element micromagnetic modeling. Base radius (
$R$
) of the conical disk is varied between 50 and 100 nm. Top radius (
$r$
) of the conical nanodisk is also varied, such that the ratio
$\sigma =r/R $
lies between 0.1 and 1. When the magnetic field is applied along the axis of the 1-D chain, almost square hysteresis loops are exhibited, and corresponding coercive field increases monotonically with
$\sigma $
. Correspondingly, the remanent magnetization state shifts from
$c$
-state to homogeneous magnetization state when
$\sigma $
is decreased from 0.9 to 0.5 and then to buckled magnetization state as
$\sigma $
is reduced to 0.1. The remanent magnetization and coercive field monotonically decrease with an increase in the angle
$\theta $
of applied magnetic field with respect axis of the 1-D chain. This behavior is due to dominating dipolar interaction along the axis of the chain, which makes it the easy axis. The Stoner–Wohlfarth (SW) model is used to approximately estimate the effective uniaxial anisotropy constant arising due to the demagnetization effect of the 1-D chain of conical nanodisks.