New York University

Huanlong Liu

Andrew David Kent

Daniel Bedau

A high speed, low power method to control and switch the magnetization direction of a magnetic region in a magnetic device for memory cells using spin polarized electrical current. The magnetic device comprises a pinned magnetic layer, a reference magnetic layer with a fixed magnetization direction and a free magnetic layer with a changeable magnetization direction. The magnetic layers are separated by insulating non-magnetic layers. A current can be applied to the device to induce a torque that alters the magnetic state of the device so that it can act as a magnetic memory for writing information. The resistance, which depends on the magnetic state of the device, can be measured to read out the information stored in the device.

Current induced spin-momentum transfer stack with dual insulating layers

A magnetic device that includes a perpendicular magnetized polarizing layer configured to provide a first spin-torque and an in-plane magnetized free layer having a magnetization vector having at least a first stable state and a second stable state. The magnetic device also includes a reference layer configured to provide a second spin-torque. The first spin-torque and the second spin-torque can combine. The in-plane magnetized free layer and the reference layer form a magnetic tunnel junction and the combined first spin-torque and second spin-torque influences the magnetic state of the in-plane magnetized free layer. An application of a voltage pulse, having either positive or negative polarity and a selected amplitude and duration, through the magnetic device causes the magnetization vector to oscillate between the first stable state and the second stable state for a portion of the duration regardless of an initial state of the magnetization vector.

Precessional magnetization reversal in a magnetic tunnel junction with a perpendicular polarizer

A magnetic device includes a magnetized polarizing layer, a free magnetic layer, and a reference layer. The free magnetic layer forms a first electrode and is separated from the magnetized polarizing layer by a first non-magnetic metal layer. The free magnetic layer has a magnetization vector having a first and second stable state. The reference layer forms a second electrode and is separated from the free-magnetic layer by a second non-magnetic layer. Unipolar current is sourced through the polarizing, free magnetic and reference layers. Switching of the magnetization vector of the free magnetic layer from the first stable state to the second state is initiated by application of a first unipolar current pulse, and switching of the magnetization vector of the free magnetic layer from the second stable state to the first stable state is initiated by application of a second unipolar current pulse.

Bipolar spin-transfer switching

Orthogonal spin-torque bit cells whose spin torques from a perpendicular polarizer and an in-plane magnetized reference layer are constructively or destructively combined. An orthogonal spin-torque bit cell includes a perpendicular magnetized polarizing layer configured to provide a first spin-torque; an in-plane magnetized free layer and a reference layer configured to provide a second spin-torque. The first spin-torque and the second spin-torque combine and the combined first spin-torque and second spin-torque influences the magnetic state of the in-plane magnetized free layer. The in-plane magnetized free layer and the reference layer form a magnetic tunnel junction. The first spin-torque and second spin-torque can combine constructively to lower a switching current, increase a switching speed, and/or torque decrease an operating energy of the orthogonal spin-torque bit cell.

Precessional reversal in orthogonal spin transfer magnetic RAM devices

Orthogonal spin-transfer magnetic random access memory (OST-MRAM) uses a spin-polarizing layer magnetized perpendicularly to the free layer to achieve large spin-transfer torques and ultra-fast energy efficient switching. OST-MRAM devices that incorporate a perpendicularly magnetized spin-polarizing layer and a magnetic tunnel junction, which consists of an in-plane magnetized free layer and synthetic antiferromagnetic reference layer, exhibit improved performance over prior art devices. The switching is bipolar, occurring for positive and negative polarity pulses, consistent with a precessional reversal mechanism, and requires an energy less than 450 fJ and may be reliably observed at room temperature with 0.7 V amplitude pulses of 500 ps duration.

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New York, NY, United States of America

Huanlong Liu