Switching of perpendicularly magnetized nanomagnets with spin-orbit torques in the absence of external magnetic fields
AssigneeUniversity of Rochester
InventorsMohammad Kazemi, Engin Ipek, Eby G. Friedman
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Abstract
A base element for switching a magnetization state of a nanomagnet includes a heavy-metal strip having a surface. A ferromagnetic nanomagnet is disposed adjacent to the surface. The ferromagnetic nanomagnet has a first magnetization equilibrium state and a second magnetization equilibrium state. The first magnetization equilibrium state or the second magnetization equilibrium state is settable in an absence of an external magnetic field by a flow of electrical charge through the heavy-metal strip. A method for switching a magnetization state of a nanomagnet is also described.
Claims21
A base element for switching a magnetization state of a nanomagnet comprising:
- a heavy-metal strip having a surface;
- a ferromagnetic nanomagnet disposed adjacent to said surface, said ferromagnetic nanomagnet comprising a shape having a long axis and a short axis, said ferromagnetic nanomagnet having both a perpendicular-to-the-plane anisotropy Hkz and an in-plane anisotropy Hkx and said ferromagnetic nanomagnet having a first magnetization equilibrium state and a second magnetization equilibrium state, said first magnetization equilibrium state or said second magnetization equilibrium state settable in an absence of an external magnetic field by a flow of electrical charge through said heavy-metal strip;
- and
- wherein a direction of flow of said electrical charge through said heavy-metal strip comprises an angle ξ with respect to said short axis of said nanomagnet.
A method for switching a magnetization state of a nanomagnet comprising the steps of:
- providing a heavy-metal strip having a surface and a ferromagnetic nanomagnet disposed adjacent to said surface, said ferromagnetic nanomagnet comprising a shape having a long axis and a short axis, said ferromagnetic nanomagnet having both a perpendicular-to-the-plane anisotropy Hkz and an in-plane anisotropy Hkx, and said ferromagnetic nanomagnet having a first magnetization equilibrium state and a second magnetization equilibrium state, and wherein a direction of flow of said electrical charge through said heavy-metal strip comprises an angle ξ with respect to said short axis of said nanomagnet;
- and
- flowing an electrical charge through said heavy-metal strip in an electrical charge direction to set said magnetization state of said nanomagnet in an absence of an external magnetic field to said first magnetization equilibrium state, or to set said magnetization state to said second magnetization equilibrium state.
A method of controlling a trajectory of a perpendicular magnetization switching of a ferromagnetic layer using spin-orbit torques in the absence of any external magnetic field comprising:
- injecting a charge current Je through a heavy-metal nonmagnetic nanostrip disposed adjacent to a ferromagnetic layer to produce spin torques which drive a magnetization M out of an equilibrium state towards an in-plane of a nanomagnet;
- turning said charge current Je off after te seconds, causing a spin torque to reduce to substantially zero where M is close to an x-y plane and away from an ez axis by an angle of ϑ in a critical zone, where an effective field experienced by the magnetization of the ferromagnetic layer Heff is significantly dominated by and in-plane anisotropy Hkx, and where M passes a hard axis by precessing around said Heff;
- and
- passing the hard axis, where Heff is dominated by a perpendicular-to-the-plane anisotropy Hkz, and where M is pulled towards the new equilibrium state by precessing and damping around Heff, completing a magnetization switching.
Dependencies are inferred from the claim text.