Magnetic Resonance Studies of the Fundamental Spin-Wave Modes in Individual Submicron $\mathrm{Cu}/\mathrm{NiFe}/\mathrm{Cu}$ Perpendicularly Magnetized Disks

Spin-wave spectra of perpendicularly magnetized disks consisting of a 100 nm permalloy layer sandwiched between two Cu layers of 30 nm are measured individually by a magnetic resonance force microscope. Using 3D micromagnetic simulations, it is demonstrated that, for submicron-size diameters, the lowest energy spin-wave mode of the saturated state is not spatially uniform, but rather is localized at the center of the $\mathrm{Py}/\mathrm{Cu}$ interfaces in the region of the minimum demagnetizing field.

Figure 1

(a) Schematic of the setup showing scanning electron microscope images of the mechanical probe and (b) of the disks.

Figure 2

(a) Mechanical FMR spectra of the $\varphi =1\mu \mathrm{m}$ disk for different frequencies. (b) Strip line FMR spectra of the control thin film. The bottom figures show the linewidth versus frequency for the two lowest energy modes of the disk (c) and extended film (d).

Figure 3

(a) Mechanical FMR spectra measured on the smallest disk ($\varphi =0.5\mu \mathrm{m}$). (b) 3D simulation of the dynamical susceptibility of a single Py layer disk ($t=100\mathrm{nm}$, $\varphi =0.5\mu \mathrm{m}$). The top shows the spatial dependence ($z,r$) of the normal component of the demagnetizing field for the saturated configuration (shifted to zero at the disk center) and the transverse dynamics (${\chi }^{\prime \prime }$) of the main modes in a color code.

Figure 4

Mechanical FMR spectra of disks of different diameter at 5.6 GHz.