講演情報
[10p-PB3-17]Substrate-Temperature Dependence of Stoichiometry and Magnetic Properties in Sputtered YIG Thin Films
〇JIN MOCHIZUI1, KENSUKE HAYASHI1, SATOSHI IIHAMA1, TAKAHIRO MORIYAMA1 (1.Nagoya Univ.)
キーワード：
spintronics、YIG、sputtering
Yttrium iron garnet (Y3Fe5O12, YIG) is a low-damping ferrimagnetic insulator widely used in magnonics and spintronics.YIG films made through vapor-phase epitaxy are typically deposited using PLD, ion beam sputtering , or off-axis sputtering [1–3] and there are few reports on cases using conventional RF sputtering. In this study, we prepared YIG films deposited by RF sputtering on (111) Gd3Ga5O12 (GGG) substrates at 25~800°C to investigate the substrate temperature dependence of stoichiometry and magnetic properties for the films. All of the films were post-annealed at 750oC in the air after deposition improve the crystallinity.
The films were evaluated by VSM, XRD, SEM-EDS, and FMR. VSM measurements shows that the films grown at 25~400oC posesse clear magnetic hysteresis after annealing, with saturation magnetizations of 135.3, 141.0, and 128.0 emu/cc, respectively. In contrast, the films grown over 400oC does not show magnetic hysteresis. Figure 1 shows XRD patterns of the films grown at 25~800°C. The film peak shifts to lower angle with increasing growth temparature, indicating that the lattice parameter of the films increase with increasing growth temperature. SEM-EDS reveals that amount of Y in the films increases as growth temperature increases. Since excess Y in the garnet strucutre substitutes Fe sites and creates antisite defects [4], it causes lattice expansion and a decrease in magnetization. FMR measurement was carried out to obtain the damping constant of the films grown at 25~400°C and the values were 4.19 × 10-4 for 25°C, 7.58 × 10-4 for 200°C, and 9.62 × 10-4 for 400°C, respectively. We have found that the cation composition of YIG films deposited by RF sputtering depends significantly on the deposition temperature. This may be one of the reasons why only a few YIG films made by vapor phase epitaxy using magnetron sputtering have been reported.
The films were evaluated by VSM, XRD, SEM-EDS, and FMR. VSM measurements shows that the films grown at 25~400oC posesse clear magnetic hysteresis after annealing, with saturation magnetizations of 135.3, 141.0, and 128.0 emu/cc, respectively. In contrast, the films grown over 400oC does not show magnetic hysteresis. Figure 1 shows XRD patterns of the films grown at 25~800°C. The film peak shifts to lower angle with increasing growth temparature, indicating that the lattice parameter of the films increase with increasing growth temperature. SEM-EDS reveals that amount of Y in the films increases as growth temperature increases. Since excess Y in the garnet strucutre substitutes Fe sites and creates antisite defects [4], it causes lattice expansion and a decrease in magnetization. FMR measurement was carried out to obtain the damping constant of the films grown at 25~400°C and the values were 4.19 × 10-4 for 25°C, 7.58 × 10-4 for 200°C, and 9.62 × 10-4 for 400°C, respectively. We have found that the cation composition of YIG films deposited by RF sputtering depends significantly on the deposition temperature. This may be one of the reasons why only a few YIG films made by vapor phase epitaxy using magnetron sputtering have been reported.