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▼ [20p-E216-20] Giant spin torque diode effect induced by nonlinear spin dynamics in double-MgO magnetic tunnel junctions
Keywords:spintronics, spin torque diode effect, non-linear spin dynamics
Magnetic tunnel junctions (MTJs) have attracted attention as nano-scale microwave devices. The spin-torque diode effect using MTJ [1] is the candidate for next generation high sensitive microwave detector. Currently, the diode sensitivity of 105 V/W order has been reported [2], which is approximately 30 times higher than the limit of Schottky diode detector. Recently, we have reported that the higher diode sensitivity of 106 V/W order is observed in heat driven magnetic tunnel junctions [3]. However, the mechanism of the giant diode effect is not well understood because it cannot be explained only by the heat-driven spin torque. In this study, we discuss the nonlinear spin dynamics such as self-oscillation measured by magnoise spectrum to understand the mechanism of giant diode effect.
The samples, buffer layer | IrMn (7.0) | CoFe | Ru | CoFeB | MgO barrier (1.0) | FeB (2.0) | MgO cap (0.5) | metal cap (unit in nm), were deposited on Si | SiO2 substrates by a magnetron sputtering. The MTJ with the diameter of 190 nm was fabricated by a photolithography. The magnetic field was optimized to obtain the largest diode voltage at bias-voltage of −0.4 V. Figure 1 shows the noise spectrum of dc-biased MTJ at the resolution band width of 5 MHz. We found that the peak power of the magnoise spectrum is exponentially increasing by dc voltage. In addition, the full width at half maximum decreases approximately at V = −0.2 V as shown in Fig. 2. These results suggest that the origin of giant diode effect is the self-oscillation. This work is supported by JSPS KAKENHI Grant Number JP19K15435.
[1] A. A. Tulapurkar et al., Nature, 438, 339 (2005), [2] L. Zhang et al., Appl. Phys. Lett, 113, 102401 (2018), [3] M. Goto et al, JSAP Spring meeting, 11p-M101-15, (2019)
The samples, buffer layer | IrMn (7.0) | CoFe | Ru | CoFeB | MgO barrier (1.0) | FeB (2.0) | MgO cap (0.5) | metal cap (unit in nm), were deposited on Si | SiO2 substrates by a magnetron sputtering. The MTJ with the diameter of 190 nm was fabricated by a photolithography. The magnetic field was optimized to obtain the largest diode voltage at bias-voltage of −0.4 V. Figure 1 shows the noise spectrum of dc-biased MTJ at the resolution band width of 5 MHz. We found that the peak power of the magnoise spectrum is exponentially increasing by dc voltage. In addition, the full width at half maximum decreases approximately at V = −0.2 V as shown in Fig. 2. These results suggest that the origin of giant diode effect is the self-oscillation. This work is supported by JSPS KAKENHI Grant Number JP19K15435.
[1] A. A. Tulapurkar et al., Nature, 438, 339 (2005), [2] L. Zhang et al., Appl. Phys. Lett, 113, 102401 (2018), [3] M. Goto et al, JSAP Spring meeting, 11p-M101-15, (2019)