Cornell University

USA As Represented by Secretary of the Navy

Robert A Buhrman

Daniel C Ralph

Chi-feng Pai

Luqiao Liu

Minh-hai Nguyen

Glen A Nyberg

Sriharsha V Aradhya

Lijun Zhu

Graham E Rowlands

Oukjae Lee

Methods, systems, and devices are disclosed for enhancement of spin-orbit torque. In one aspect, a magnetic device includes a magnetic tunneling junction (MTJ), including a free magnetic layer, a pinned magnetic layer and a non-magnetic junction layer between the free magnetic layer and the pinned magnetic layer, and a spin Hall effect metal layer that includes one or more insertion metal layers operable to introduce interfacial scattering of electrons flowing in the spin Hall metal layer to increase the spin current that interacts with and changes the magnetization of the free magnetic layer of the MTJ.

Giant enhancement of spin-orbit torque by interface scattering from ultra-thin insertion layers

Devices or circuits based on spin torque transfer (STT) and Spin Hall effect are disclosed by using a spin Hall effect (SHE) metal layer coupled to a magnetic free layer for various applications. The efficiency or strength of the STT effect based on this combination of SHE and STT can be enhanced by an interface modification between the SHE metal layer and the magnetic free layer or by modifying or engineering the SHE metal layer by doping the SHE metal with certain impurities or other means.

Circuits and devices based on enhanced spin Hall effect for efficient spin transfer torque

The disclosed technology provides various implementations of a device based on a spin Hall effect (SHE) and spin transfer torque (STT) effect. In one aspect, a device is provided to include a magnetic structure including a ferromagnetic layer having a magnetization direction that can be changed by spin transfer torque; a SHE layer that is electrically conducting and exhibits a spin Hall effect to, in response to an applied charge current, generate a spin-polarized current that is perpendicular to the applied charge current, the SHE layer located adjacent to the ferromagnetic layer to inject the spin-polarized current into the ferromagnetic layer; a first electrical contact in contact with the magnetic structure; a second electrical contact in contact with a first location of the SHE layer; a third electrical contact in contact with a second location of the SHE layer so that the first and second locations are on two opposite sides of the magnetic structure; a magnetic structure circuit coupled between the first electrical contact and one of the second and third electrical contacts to supply a current or a voltage to the magnetic structure; and a charge current circuit coupled between the second and third electrical contacts to supply the charge current into the SHE layer, wherein the device is operable at a low write error rate with pulses of a pulse duration of around 2 ns or shorter to switch a direction of the magnetization direction of the ferromagnetic layer in the magnetic structure.

Nanosecond-timescale low-error switching of 3-terminal magnetic tunnel junction circuits through dynamic in-plane-field assisted spin-hall effect

Circuits and devices based on enhanced spin hall effect for efficient spin transfer torque

Three-terminal magnetic circuits and devices based on the spin-transfer torque (STT) effect via a combination of injection of spin-polarized electrons or charged particles by using a charge current in a spin Hall effect metal layer coupled to a free magnetic layer and application of a gate voltage to the free magnetic layer to manipulate the magnetization of the free magnetic layer for various applications, including nonvolatile memory functions, logic functions and others. The charge current is applied to the spin Hall effect metal layer via first and second electrical terminals and the gate voltage is applied between a third electrical terminal and either of the first and second electrical terminals. The spin Hall effect metal layer can be adjacent to the free magnetic layer or in direct contact with the free magnetic layer to allow a spin-polarized current generated via a spin Hall effect under the charge current to enter the free magnetic layer. The disclosed three-terminal magnetic circuits can also be applied to signal oscillator circuits and other applications.

Electrically gated three-terminal circuits and devices based on spin hall torque effects in magnetic nanostructures apparatus, methods and applications

A device based on a spin Hall effect and spin-transfer torque (STT) effect is provided to include a magnetic tunneling junction (MTJ) element including a free magnetic layer structured to have a magnetization direction that can be changed by spin-transfer torque; an electrically conducting magnetic layer structure exhibiting a spin Hall effect (SHE) and, in response to an applied in-plane charge current, generating a spin-polarized current of a magnetic moment oriented in a predetermined direction having both an in-plane magnetic moment component parallel to a surface of the electrically conducting magnetic layer structure and a perpendicular magnetic moment component perpendicular to the surface of the electrically conducting magnetic layer structure. The magnetization direction of the free magnetic layer is capable of being switched by the spin-polarized current via a spin-transfer torque (STT) effect. This device can be configured in a 3-terminal configuration.

Circuits and devices based on spin hall effect to apply a spin transfer torque with a component perpendicular to the plane of magnetic layers

Techniques, systems, and devices are disclosed for implementing a quasi-linear spin-torque nano-oscillator based on exertion of a spin-transfer torque on the local magnetic moments in the magnetic layer and precession of the magnetic moments in the magnetic layer within a spin valve. Examples of spin-torque nano-oscillators (STNOs) are disclosed to use spin polarized currents to excite nano magnets that undergo persistent oscillations at RF or microwave frequencies. The spin currents are applied in a non-uniform manner to both excite the nano magnets into oscillations and generate dynamic damping at large amplitude as a feedback to reduce the nonlinearity associated with mixing amplitude and phase fluctuations.

Quasi-linear spin torque nano-oscillators

An ST-MRAM structure, a method for fabricating the ST-MRAM structure and a method for operating an ST-MRAM device that results from the ST-MRAM structure each utilize a spin Hall effect base layer that contacts a magnetic free layer and effects a magnetic moment switching within the magnetic free layer as a result of a lateral switching current within the spin Hall effect base layer. This resulting ST-MRAM device uses an independent sense current and sense voltage through a magnetoresistive stack that includes a pinned layer, a non-magnetic spacer layer and the magnetic free layer which contacts the spin Hall effect base layer. Desirable non-magnetic conductor materials for the spin Hall effect base layer include certain types of tantalum materials and tungsten materials that have a spin diffusion length no greater than about five times the thickness of the spin Hall effect base layer and a spin Hall angle at least about 0.05.

Spin hall effect magnetic apparatus, method and applications

3-terminal magnetic circuits and devices based on the spin-transfer torque (STT) effect via a combination of injection of spin-polarized electrons or charged particles by using a charge current in a spin Hall effect metal layer coupled to a free magnetic layer and application of a gate voltage to the free magnetic layer to manipulate the magnetization of the free magnetic layer for various applications, including non-volatile memory functions, logic functions and others. The charge current is applied to the spin Hall effect metal layer via first and second electrical terminals and the gate voltage is applied between a third electrical terminal and either of the first and second electrical terminals. The spin Hall effect metal layer can be adjacent to the free magnetic layer or in direct contact with the free magnetic layer to allow a spin-polarized current generated via a spin Hall effect under the charge current to enter the free magnetic layer. The disclosed 3-terminal magnetic circuits can also be applied to signal oscillator circuits and other applications.

A method of producing high quality stoichiometric thin films of vanadium dioxide by reactive evaporation utilizes an electron beam to evaporate a source of vanadium in a controlled, low pressure oxygen gas environment with the film being deposited at a predetermined rate onto a substrate which is heated to and maintained at a predetermined temperature above 500.degree. C.

Growing community of inventors

Ithaca, NY, United States of America

Robert A Buhrman