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▲ [9p-PB1-10] Magnetic damping in Pt/Co/Cr2O3/Pt stack films with perpendicular magnetic anisotropy
Keywords:Broadband - FMR, Magnetic damping, Perpendicular Magnetic Anisotropy
Magnetization dynamics in ferromagnetic (FM)/non-magnetic (NM) stack films with perpendicular magnetic anisotropy (PMA) is of increasing interest in a realization of spintronics devices. One of the most dominant parameters for understanding the dynamics is the Gilbert damping constant (α), which determines the strength of damping torque in the system. Many reports focused on the investigation of the correlation between α and PMA. However, the relationship is still controversial and the results are dispersed among the variation of the film stack. Thus, a systematic investigation is required. Herein, we choose perpendicularly magnetized Pt/Co stack films as a typical FM/NM system showing PMA, and we investigate the change in α and PMA with the thickness of Co (tCo) and Pt (tPt) layers, and then discuss their correlation in these stack films.
Pt(tPt)/Co(tCo)/Cr2O3(200 nm)/Pt stack films were deposited by DC magnetron sputtering. Cr2O3 is a typical insulator, which enabled us to focus on the magnetization dynamics at the interface between Co(tCo) and capped Pt(tPt) layers. α and uniaxial magnetic anisotropy energy (KU) were then investigated by a broadband ferromagnetic resonance and a vibrating sample magnetometer at room temperature, respectively.
In Fig. 1(a), KU decreases as tCo increases because of the interfacial nature of PMA. α also decreases with tCo accompanied with KU. These results demonstrate that α is correlated with KU in these stack films through the strong spin-orbit interaction. On the other hand, in Fig. 1(b), α increases with the increase of tPt for tPt< 5 nm, and almost keeps constant for tPt> 5 nm, while KU increases with the increase of tPt. The behavior of α can be explained by the spin pumping at the interface of the capped Pt and Co layers.
Pt(tPt)/Co(tCo)/Cr2O3(200 nm)/Pt stack films were deposited by DC magnetron sputtering. Cr2O3 is a typical insulator, which enabled us to focus on the magnetization dynamics at the interface between Co(tCo) and capped Pt(tPt) layers. α and uniaxial magnetic anisotropy energy (KU) were then investigated by a broadband ferromagnetic resonance and a vibrating sample magnetometer at room temperature, respectively.
In Fig. 1(a), KU decreases as tCo increases because of the interfacial nature of PMA. α also decreases with tCo accompanied with KU. These results demonstrate that α is correlated with KU in these stack films through the strong spin-orbit interaction. On the other hand, in Fig. 1(b), α increases with the increase of tPt for tPt< 5 nm, and almost keeps constant for tPt> 5 nm, while KU increases with the increase of tPt. The behavior of α can be explained by the spin pumping at the interface of the capped Pt and Co layers.