Thin films were deposited by DC magnetron sputtering with a base pressure of less than 2 × 10−8 torr. In an attempt to produce high-quality L10-IrMn and to avoid problems with post-annealing, we deposited IrMn at elevated temperature. We tried a few substrates of small lattice mismatch, among which L10-IrMn of high chemical order and sufficiently smooth surface was produced only when the KTaO3 substrate was used. Because of island growth at high temperature, L10-IrMn of less than 10 nm became discontinuous with high roughness and large electrical resistivity. Therefore, the thickness of our L10-IrMn was larger than past reports. In addition, considerable loss of Mn was observed at temperatures higher than 500°C, probably due to its high vapor pressure. Thus, our L10-IrMn was produced by first baking the KTaO3 (001) substrate at 720°C for 30 min and then co-sputtering 5.08-cm Ir40Mn60 [atomic % (at %)] and Mn targets at the same temperature. Polycrystalline FCC IrMn as well as polycrystalline Py and Pt were deposited in situ at room temperature. All polycrystalline samples were deposited on the SiO2 substrate. Because of strong exchange coupling between Py and L10-IrMn, Py of less than 10 nm exhibited a substantially larger coercive field and linewidth. The former introduced measurement artifacts in ST-FMR for smaller frequencies; the latter reduced the signal-to-noise ratio. Therefore, Py in this work was also thicker than past reports. A 2-nm SiO2 was deposited by radio frequency (rf) magnetron sputtering on all samples as the protective layer. In this work, the nominal thicknesses of films were calibrated using an atomic force microscope. The real thicknesses were obtained from HRTEM, which were typically around 85% of the nominal ones. Thus, a nominal 25 nm became 22 nm and a nominal 15 nm became 13 nm, etc.

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