Ferromagnetic resonance force spectroscopy of individual submicron-size samples

Abstract

We review how a magnetic resonance force microscope (MRFM) can be applied to perform ferromagnetic resonance (FMR) spectroscopy of individual sub-micron size samples. We restrict our attention to a thorough study of the spin-wave eigen-modes excited in permalloy (Py) disks patterned out of the same 43.3 nm thin film. The disks have a diameter of either 1.0 or 0.5 µm and are quasi-saturated by a perpendicularly applied magnetic field. It is shown that quantitative spectroscopic information can be extracted from the MRFM measurements. In particular, the data are extensively compared with complementary approximate models of the dynamical susceptibility: i) a 2D analytical model, which assumes an homogeneous magnetization dynamics along the thickness and ii) a full 3D micromagnetic simulation, which assumes an homogeneous magnetization dynamics below a characteristic length scale c and which approximates the cylindrical sample volume by a discretized representation with regular cubic mesh of lateral size c = 3.9 nm. In our analysis, the distortions due to a breaking of the axial symmetry are taken into account, both models incorporating the possibility of a small misalignment between the applied field and the normal of the disks.

Measurement of the intrinsic damping constant in individual nanodisks of Y3Fe5O12 and Y3Fe5O12|Pt

“…12 The splitting corresponds to the quantization of the SW wavenumber / np=/ (where n being an integer) in the radial direction. 11 One can thus infer from the peak separation the lateral size of the disk. Using the literature 13,14 value for the YIG exchange length K ex ¼ 15 nm, a fit of the peak separation leads to an effective confinement of, respectively, 700, 520, 380 nm for our 3 disks, assuming total pinning at the disk edge (see Table II).…”

“…11 It is based on measuring the deflection of a cantilever with a magnetic Fe particle of about 800 nm diameter affixed to the tip. The tip magnetic dipole moment senses the stray field produced by the perpendicular component M z of the magnetization of the magnetic nanodisks, which is modulated by the exciting microwave power at the mechanical frequency of the cantilever.…”

Magnetic Vortices in Ferromagnetic Nanodots

“…This leads to the change in the magnet effective energy, core mass and the gyromagnetic constant. This causes the variation in the frequency of gyrotropic motion [9,20,21,23]. …”

Spectroscopy and Imaging of Edge Modes in Permalloy Nanodisks

“…X-ray microscopy based on magnetic circular dichroism also provides dynamic magnetic imaging [18][19][20] with resolution as fine as 25 nm. [18] In parallel, ferromagnetic resonance force microscopy (FMRFM) [21][22][23][24] has been developed and proven to be a useful tool for various areas in magnetic dynamics, such as spin wave dynamics in confined structures [22,[25][26][27][28][29][30], spin-transfer torque device dynamics [31], defect detection in an array [32], and spin wave localization [33][34][35][36]. With spin waves localized by the stray field from the FMRFM tip, a resolution of 200 nm has been reported [33].…”

“…The square of the precession amplitude is thus measured via the cantilever oscillation amplitude. [22] A 100 nm diameter roughly hemispherical tip of cobalt is used in this study. The tip was fabricated through electron beam induced deposition (EBID) [39], and a scanning electron microscope (SEM) image of the tip is shown in the inset of Fig.…”