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Capacitance effect on the oscillation and switching characteristics of spin torque oscillators.

Zeng T, Zhou Y, Leung CW, Lai PP, Pong PW - Nanoscale Res Lett (2014)

Bottom Line: The switching characteristic is featured with the emerging of the canted region; the canted region increases with the capacitance.When the external field is absent, the STO free-layer switching time exhibits different dependences on the capacitance for different injected current.These results help to establish the foundation for capacitance-involved STO modeling.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam, Hong Kong.

ABSTRACT
We have studied the capacitance effect on the oscillation characteristics and the switching characteristics of the spin torque oscillators (STOs). We found that when the external field is applied, the STO oscillation frequency exhibits various dependences on the capacitance for injected current ranging from 8 to 20 mA. The switching characteristic is featured with the emerging of the canted region; the canted region increases with the capacitance. When the external field is absent, the STO free-layer switching time exhibits different dependences on the capacitance for different injected current. These results help to establish the foundation for capacitance-involved STO modeling.

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When Happ = 0.05 T, C = 0. 1 pF. (a) Time-evolved STO resistance for Idc =114 mA and Idc = 246 mA. (b) Free-layer magnetization switching trajectory for Idc = 246 mA. (c) Free-layer magnetization switching trajectory for Idc = 114 mA.
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Figure 3: When Happ = 0.05 T, C = 0. 1 pF. (a) Time-evolved STO resistance for Idc =114 mA and Idc = 246 mA. (b) Free-layer magnetization switching trajectory for Idc = 246 mA. (c) Free-layer magnetization switching trajectory for Idc = 114 mA.

Mentions: In Part A, it is discussed how the oscillation frequency behaves under different capacitance values. However, it is worth noting that as the injected current Idc increases to a critical value, the balance between the injected spin torque and damping cannot be maintained. The injected spin torque overwhelms the damping, resulting in the reversal of the free-layer magnetization from parallel state to anti-parallel. However, in the case where the capacitance value is set to 0.1 pF (Figure 3), when the injected current Idc increases gradually to 114 mA, the magnetization switches from parallel state to a canted state instead of anti-parallel state. The magnetization trajectory in Figure 3c suggests that the magnetization finally stays in a static state with a canted angle. When Idc continues to increase to 246 mA, complete magnetization reversal is achieved from parallel state to anti-parallel state, as shown in Figure 3b. This concludes that the existence of the capacitance realizes a canted region (from 114 to 246 mA in this case) as a transition between parallel state and anti-parallel state. It has also been verified that without the capacitance, no canted region is observed in this system.


Capacitance effect on the oscillation and switching characteristics of spin torque oscillators.

Zeng T, Zhou Y, Leung CW, Lai PP, Pong PW - Nanoscale Res Lett (2014)

When Happ = 0.05 T, C = 0. 1 pF. (a) Time-evolved STO resistance for Idc =114 mA and Idc = 246 mA. (b) Free-layer magnetization switching trajectory for Idc = 246 mA. (c) Free-layer magnetization switching trajectory for Idc = 114 mA.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
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getmorefigures.php?uid=PMC4230906&req=5

Figure 3: When Happ = 0.05 T, C = 0. 1 pF. (a) Time-evolved STO resistance for Idc =114 mA and Idc = 246 mA. (b) Free-layer magnetization switching trajectory for Idc = 246 mA. (c) Free-layer magnetization switching trajectory for Idc = 114 mA.
Mentions: In Part A, it is discussed how the oscillation frequency behaves under different capacitance values. However, it is worth noting that as the injected current Idc increases to a critical value, the balance between the injected spin torque and damping cannot be maintained. The injected spin torque overwhelms the damping, resulting in the reversal of the free-layer magnetization from parallel state to anti-parallel. However, in the case where the capacitance value is set to 0.1 pF (Figure 3), when the injected current Idc increases gradually to 114 mA, the magnetization switches from parallel state to a canted state instead of anti-parallel state. The magnetization trajectory in Figure 3c suggests that the magnetization finally stays in a static state with a canted angle. When Idc continues to increase to 246 mA, complete magnetization reversal is achieved from parallel state to anti-parallel state, as shown in Figure 3b. This concludes that the existence of the capacitance realizes a canted region (from 114 to 246 mA in this case) as a transition between parallel state and anti-parallel state. It has also been verified that without the capacitance, no canted region is observed in this system.

Bottom Line: The switching characteristic is featured with the emerging of the canted region; the canted region increases with the capacitance.When the external field is absent, the STO free-layer switching time exhibits different dependences on the capacitance for different injected current.These results help to establish the foundation for capacitance-involved STO modeling.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam, Hong Kong.

ABSTRACT
We have studied the capacitance effect on the oscillation characteristics and the switching characteristics of the spin torque oscillators (STOs). We found that when the external field is applied, the STO oscillation frequency exhibits various dependences on the capacitance for injected current ranging from 8 to 20 mA. The switching characteristic is featured with the emerging of the canted region; the canted region increases with the capacitance. When the external field is absent, the STO free-layer switching time exhibits different dependences on the capacitance for different injected current. These results help to establish the foundation for capacitance-involved STO modeling.

No MeSH data available.


Related in: MedlinePlus