Comparison of frequency, field, and time domain ferromagnetic resonance methods

Abstract

We present vector network analyzer ferromagnetic resonance measurements of epitaxial Fe films having a thickness of 16 monolayers. Our objective is to test the reliability of this novel frequency domain technique with respect to frequency and damping. For this purpose we compare vector network analyzer ferromagnetic resonance to pulsed inductive microwave magnetometry, time resolved magnetooptic Kerr effect (both methods in the time domain), and conventional ferromagnetic resonance (measured in the field domain) in terms of position and width of the ferromagnetic resonance. In addition, we compare the various techniques with respect to the signal to noise ratio of the raw data. All data is obtained using the same well characterized ultrathin magnetic Fe/GaAs (0 0 1) film. Finally, we demonstrate the potential of the vector network analyzer ferromagnetic resonance technique for the investigation of nano-structured magnetic elements having nonuniform magnetization configuration. The absorption spectrum of Permalloy disks with a diameter of 200 nm and a thickness of 15 nm shows up to eight distinct resonance peaks. The spatial structure of the corresponding modes was derived from numerical calculations and reveals that azimuthal modes up to the fifth order have been observed inductively. r

Optically induced magnetization dynamics and variation of damping parameter in epitaxialCo2MnSiHeusler alloy films

“…However, TRMOKE samples a small spot of 100 m size while in FMR, the entire 10 mm 2 sample is placed within the microwave cavity, so inhomogeneous broadening is expected to be more severe in the case of FMR. 23 The smaller values of ␣ obtained by Yilgin et al may in part be due to the different methods used to account for the contribution of inhomogeneous broadening to the FMR linewidth. Also, it should be noted that the beam from the regenerative laser amplifier system may become very slightly divergent or convergent as the alignment of the amplifier is adjusted from day to day.…”

“…22 Differences in damping have been found when direct comparison has been made between different frequency, field and time domain techniques. 23 Time-resolved optical measurements have the advantage that they can probe a much smaller volume than microwave resonance experiments, but may be susceptible to additional contributions to the damping. For example, the spatial profile of a pulsed magnetic field or a focused pump laser spot may lead to the generation of magnons that propagate away from the region that is being probed.…”

Microwave spectroscopy with vector network analyzer for interlayer exchange-coupled symmetrical and asymmetrical NiFe/Ru/NiFe

“…For the dynamic measurements using VNA-FMR spectroscopy, the samples of 1 × 1 cm 2 are coupled to a coplanar waveguide; more details on the experimental set-up can be found in [10]. For the conventional configuration of measurement (see figure 1(c)), the data at each bias field (H 0 ) require the subtraction of two measurements: one with the bias field switched on and a second measurement with a 1 kOe saturating field applied in the same direction as the rf field (h rf ), The developed configuration (longitudinal) was inspired from the longitudinal FMR technique [8,9].…”

Spin waves in circular soft magnetic dots at the crossover between vortex and single domain state

“…The lowest frequency excitation corresponds to the gyrotropic mode when the vortex moves as a whole around an equilibrium position [7][8][9], meanwhile the higher frequency modes correspond to the spin waves excited mainly outside of the vortex core [10][11][12][13][14][15][16][17][18][19]. The spin wave having radial or azimuthal symmetry with respect to the dot center are described by integers (n, m), which indicate number of nodes in the dynamic magnetization along radial (n) and azimuthal (m) directions.…”