Oscillating-field assisted spin torque switching of a magnetic tunnel junction memory element
First Claim
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1. A magnetic memory device, comprising:
- a memory cell comprising a magnetic tunnel junction which comprises a free magnetic layer, a pinned magnetic layer and a spacer layer which is nonmagnetic and located between the pinned magnetic layer and the free magnetic layer;
a first mechanism to apply an AC current to produce an oscillating magnetic field at an oscillating frequency in resonance with a magnetic resonance frequency of the free magnetic layer and to magnetically couple the oscillating magnetic field to the free magnetic layer; and
a second mechanism to apply a DC current across the magnetic tunnel junction of the memory cell to cause a spin transfer torque in the free magnetic layer,wherein a magnitude of each of the oscillating magnetic field by the AC current and the spin transfer torque by the DC current alone and without the other is less than a threshold for changing a magnetization direction of the free magnetic layer.
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Abstract
Devices and techniques for applying a resonant action by an applied oscillating magnetic field to a magnetic tunnel junction (MTJ) and an action of an applied DC current across the MTJ to effectuate a switching of the MTJ when writing data to the MTJ.
414 Citations
23 Claims
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1. A magnetic memory device, comprising:
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a memory cell comprising a magnetic tunnel junction which comprises a free magnetic layer, a pinned magnetic layer and a spacer layer which is nonmagnetic and located between the pinned magnetic layer and the free magnetic layer; a first mechanism to apply an AC current to produce an oscillating magnetic field at an oscillating frequency in resonance with a magnetic resonance frequency of the free magnetic layer and to magnetically couple the oscillating magnetic field to the free magnetic layer; and a second mechanism to apply a DC current across the magnetic tunnel junction of the memory cell to cause a spin transfer torque in the free magnetic layer, wherein a magnitude of each of the oscillating magnetic field by the AC current and the spin transfer torque by the DC current alone and without the other is less than a threshold for changing a magnetization direction of the free magnetic layer. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 21)
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16. A method for operating a memory cell comprising a magnetic tunnel junction, comprising:
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applying an AC current to produce an oscillating field at an oscillating frequency and in resonance with a magnetic resonance frequency of a free magnetic layer of the magnetic tunnel junction and to magnetically couple the oscillating field to the free magnetic layer; applying a DC current across the magnetic tunnel junction to cause a spin transfer torque in the free magnetic layer; and controlling the AC and DC currents to be applied simultaneously to switch a magnetic orientation of the free magnetic layer. - View Dependent Claims (17, 18, 19, 20)
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22. A magnetic memory device, comprising:
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a substrate; a plurality of memory cells at different locations on the substrate and arranged in rows and columns, each memory cell comprising a magnetic tunnel junction which comprises a free magnetic layer, a pinned magnetic layer and a spacer layer which is nonmagnetic and located between the pinned magnetic layer and the free magnetic layer; an AC signal source to produce an AC current at an oscillating frequency in resonance with a magnetic resonance frequency of the free magnetic layer; a plurality of first conductor lines coupled to different rows of memory cells, respectively, each first conductor line electrically coupled to a corresponding row of memory cells and coupled to receive the AC current and to magnetically couple the oscillating magnetic field to the free magnetic layer of each memory cell of the corresponding row; a plurality of second conductor lines coupled to different columns of memory cells, respectively, each second conductor line electrically coupled to supply a DC current to a corresponding column of memory cells wherein the DC current flows across the magnetic tunnel junction of each memory cell to cause a spin transfer torque in the free magnetic layer, wherein a magnitude of each of the oscillating magnetic field by the AC current and the spin transfer torque by the DC current alone and without the other is less than a threshold for changing a magnetization direction of the free magnetic layer of each memory cell, and wherein the oscillating magnetic field by the AC current and the spin transfer torque by the DC current in combination exceed the threshold and thus change the magnetization direction of the free magnetic layer when the AC current and the DC current are applied to the memory cell at the same time, and a control mechanism to control application of the AC current and the DC current to select one or more memory cells to switch. - View Dependent Claims (23)
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Specification