DOI: 10.24378/exe.3343
title: Optically detected spin-orbit torque ferromagnetic resonance in an in-plane magnetized ellipse (dataset)

description: Time-resolved scanning Kerr microscopy has been used to perform optically detected, phase-resolved spin–orbit torque ferromagnetic resonance (SOT-FMR) measurements on a microscale CoFeB ellipse at the center of a Pt Hall cross subject to RF and DC current. Time-resolved polar Kerr images revealed localized dynamics with large amplitude at the center and weaker amplitude at the edges. Therefore, field swept SOT-FMR spectra were acquired from the so-called center mode to probe the SOTs active at the center of the ellipse, thus minimizing nonuniform edge contributions. When the magnetic field was applied at 30° from the hard axis of the ellipse and a DC current was applied, a marked asymmetry was observed in the amplitude and linewidth of the FMR peaks as the applied field was reversed. Both absorptive and dispersive parts of the spectra were in good agreement with a macrospin calculation. The damping parameter (α) and the Slonczewski torque parameter were determined to be 0.025 and (6.75±0.75)×10−7 Oe A−1 cm2, respectively. The hard axis SOT-FMR linewidth was found to be almost independent of the DC current value, suggesting that the SOT has a minimal influence in the hard axis configuration and that thermal effects were insignificant. This study paves the way for spatially resolved measurements of SOT probed using localized modes of microscale devices that go beyond the spatially averaged capability of electrical measurement techniques.
description: Underlying data sets The underlying data sets used to generate figures for the manuscript and supplemental information are provided. Below the data files, data set folder, and analysis files corresponding to each figure are listed. Particular file names are listed and may be found within associated Origin Projects or the original data set. Data sets are separated into folders containing ‘experiment data’ or results of ‘macrospin calculation.’ For a particular date (format: yymmdd) data is located within the corresponding folder along with a text file (name format: yymmdd##labbook/labnotes/notes.txt or similar) that contains corresponding lab notes. LabVIEW was used to plot Kerr images. Origin Pro was used to analyse STT-FMR spectra. MATLAB was used to perform macrospin calculations. Yellow highlighted bold type parameters in brackets in file names listed below correspond to changing file number/experiment parameter, e.g. ST[0-10] corresponds to changing the Slonczewski torque parameter from 0 to 10×10-7 Oe A-1 cm2. Measured SOT-FMR spectrum files contain the following data columns; column 1 magnetic field recorded as voltage applied to the electromagnet power supply (where 8 V ~ 1 kOe and most spectra were acquired for a field swept linearly with voltage in the range ±4 V or ±500 Oe), column 2 is not in use, column 3 is DC reflectivity, and columns 4 and 5 are the X and Y analogue outputs of the lock-in amplifier used to recover the dynamic polar Kerr signal. The lock-in amplifier reference phase was adjusted so that the dynamic Kerr signal was mostly present in channel X only. TR scan data files contain suitable headers. Macrospin calculation files contain the following data columns: HB, Re{χyx} corresponding to my, Im{χyx} corresponding to my, f0, φ, θ, my, mpar, mperp, where mpar and mperp are the magnetization unit vectors parallel and perpendicular to the applied magnetic field, and all other variables are defined in the supplementary material.
description: The article associated with this dataset is available in ORE at: http://hdl.handle.net/10871/125071