Electrically gated three-terminal circuits and devices based on spin hall torque effects in magnetic nanostructures apparatus, methods 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.
1. A device for generating an oscillation signal based on a magnetic tunneling junction in a three-terminal circuit configuration, comprising:
a magnetic tunneling junction (MTJ) that includes (1) a pinned magnetic layer having a fixed magnetization direction in the pinned magnetic layer, (2) a free magnetic layer having a magnetization direction that is in the free magnetic layer and is changeable, and (3) a non-magnetic junction layer between the magnetic free layer and the pinned magnetic layer and formed of an insulator material sufficiently thin to allow tunneling of electrons between the magnetic free layer and the pinned magnetic layer;
a spin Hall effect metal layer that is nonmagnetic and includes a metal exhibiting a large spin Hall effect to react to a charge current directed into the spin Hall effect metal layer to produce a spin-polarized current that is perpendicular to the charge current, the spin Hall effect metal layer being parallel to and adjacent to the free magnetic layer to direct the spin-polarized current generated in the spin Hall effect metal layer into the free magnetic layer;
a first electrical terminal in electrical contact with the MTJ from a side having the pinned magnetic layer; and
second and third electrical terminals in electrical contact with two contact locations of the spin Hall effect metal layer on two opposite sides of the free magnetic layer to supply the charge current in the spin Hall effect metal layer; and
a control circuit coupled to the first, second and third electrical terminals to supply (1) a constant current as the charge current via the second and third electrical terminals in the spin Hall effect metal layer to cause a precession of the magnetization of the free magnetic layer due to the spin-polarized current produced by the spin Hall effect metal layer, and (2) a MTJ junction current directed via the first electrical terminal across the MTJ to cause a current tunneling across the MTJ that oscillates due to the precession of the of the magnetization of the free magnetic layer,
wherein the control circuit is configured to adjust the MTJ junction current to control an oscillation frequency or an amplitude of the oscillation in the current tunneling across the MTJ.
2. The device as in claim 1 , wherein:
the control circuit includes a first current source coupled to the second electrical terminal to supply the constant current in the spin Hall effect metal layer and a second current coupled to the first electrical terminal to supply the MTJ junction current.
3. The device as in claim 1 , wherein:
each of the pinned and free magnetic layers has a magnetization direction perpendicular to the layer,
the device further includes a magnetic mechanism to produce a magnetic bias field at the free magnetic layer and in a field direction parallel to the free magnetic layer.
4. The device as in claim 1 , wherein:
the magnetic element includes a magnetic layer that produces the magnetic bias field and is located between the first electrical terminal and the spin Hall effect metal layer.
5. The device as in claim 4 , wherein:
each memory cell includes a non-magnetic spacer layer in contact with the pinned magnetic layer, and
the magnetic layer is in contact with the non-magnetic spacer layer and configured to have a magnetization direction in the magnetic layer to produce the bias magnetic field in the free magnetic layer.