Supplemental to Platinum or palladium: reasonable choice in spintronic devices
Description
Fig. S1. XRD spectrum of sample 2. Fig. S2. Cross-sectional EDX spectra of the samples 1 (a) and 2 (b). Fig. S3. In-plane and out-of-plane hysteresis loops, recorded at room temperature, for Pt-based series samples: [Pt(3.2 nm)/Co(1.0 nm)/Ir(1.4 nm)/Co(tCo)/Pt(3.2 nm)] with the thick layer (a) tCo = 0.6 nm, (b) tCo = 0.7 nm, (c) tCo = 0.8 nm, (d) tCo = 1.0 nm and for Pd-based series samples Pd(3.2 nm)/Co(1.0 nm)/Ir(tIr)/Co(0.8 nm)/Pd(3.2 nm) with (e) tIr = 1.4 nm, (f) tIr = 1.2 nm, (g) tIr = 1.0 nm. Fig. S4. Orientations of the magnetic field, laser beam and wave vector of the spin wave in respect to the sample Fig. S5. Dependence of the transition field on temperature for sample 1. Fig. S6. Dependence of the transition field on temperature for sample 2.
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The samples were deposited on glass substrates of 3 * 20 mm2 area in a Nordiko 2000 magnetron sputtering system equipped with 6 targets. The base pressure prior to the sample deposition was lower than 2.1x10-7 Torr. The Pd, Pt and Ta targets were deposited using DC magnetron sputtering, whilst the Ir and Co targets were deposited using RF power. Calibration of the deposition rates from Ir target was performed by adjustment of Ar gas work pressure within a range between 3 mTorr and 8 mTorr to achieve the deposition rate of 0.027 nm/s. Thus, we have selected this thickness of Ir in both the Pt-based reference sample 1 and the the Pd-based sample 2, to reveal the effect of Pt to Pd substitution having other conditions unchanged. The XRD (X-ray Diffraction) spectrum was obtained using an Aeris X-ray diffractometer (manufactured by Malvern PANalytical B.V., the Netherlands, 2020) equipped with HIGH SCORE software. The X-ray diffractometer had a copper tube Kα1 x rays with a wavelength of 1.54 Å. The measurements were made in the range of angles 2θ = 5°– 80 ° with a step of 0.012 °.The XRD spectrum analysis was performed in the Crystallographica Search-Match program (Fig. S1). EDX analysis (energy dispersive X-ray spectroscopy) was obtained using a SUPRA 25 (Zeiss) scanning electron microscope (SEM) equipped with a Superprobe-733 (JEOL) module with an Inca Energy EDX analyzer. The area of the analyzed region was ~ 1 μm2. The penetration depth of X-rays was ~ 1 μm. The EDX spectra, recorded from surface (Fig. 1) and cross-section (Fig. S2) of the samples 1 and 2, confirm the composition of the layers in the structures. Magnetic hysteresis loops in the temperature range of 2 – 300 K and magnetic fields from 0 to 1 T were obtained using a Quantum Design MPMS 5XL SQUID magnetometer. The magnetic field was perpendicular to the film (i.e., along the easy axis). Additional in-plane and out-of-plane measurements confirming perpendicular magnetic anisotropy across the entire sample series are presented in Fig. S3. In BLS experiments, a focused monochromatic beam of 532 nm wavelength was generated by Excelsior (Spectra Physics) EXLSR–532–200–CDRH laser source. The light beam was focused to a 25 μm spot on sample surface at power of 20 mW. The light penetration depth was 30–40 nm, which was well enough to penetrate through all the layers in the heterostructures down to substrate. The frequency difference between Stokes and anti-Stokes peaks in the BLS spectrum was determined at in-plane field H = +8 kOe. Light scattering spectra were measured by the BLS method at room temperature in the Damon–Eshbach geometry (Fig. S4).