Thickness Dependence of Two Resonance Modes in NiFe/CoFe Bilayer
| Autor: | Hong-Bin Lu, 盧宏斌 |
|---|---|
| Rok vydání: | 2019 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 107 In our findings, when total thickness of NiFe/CoFe bilayer is ≧48.5 nm and frequency > 8 GHz, two ferromagnetic resonance peaks, which are called optical mode and acoustic mode, can be observed. The relation of exchange coupling field (H_ex) of optical mode and thickness of CoFe and NiFe is that when NiFe thickness is fixed at 43.5 nm and we vary CoFe thickness, H_ex ∝ t_CoFe to the power of -0.6; when CoFe thickness is fixed at 30 nm and we vary NiFe thickness, H_ex ∝ t_NiFe to the power of -1.88. By analyzing H_ex and effective magnetization (M_eff), it is found that in optical mode, FMR signal is mainly contributed by CoFe, and the large H_ex can be explained by standing spin wave. In acoustic mode, when NiFe is thicker than 28.5 nm, FMR M_eff is mainly contributed by NiFe; when NiFe is thinner than 28.5 nm, FMR M_eff is contributed by NiFe and CoFe. H_ex is attributed to interface magnetization pinning, which provides a field that is parallel to the orientation of magnetization[1]. H_ex of acoustic mode increases with CoFe and NiFe thickness. The change of absorption peak amplitude with frequency meets previous theoretical calculation, and this behavior can be explained by skin effect of microwave in conductor[2]. The results of hysteresis loops show that the saturation magnetization Ms and coercivity Hc of different thickness do not fit well with the theory, but follow similar trends. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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