Voltage-controlled magnetic anisotropy (VCMA) switch and magneto-electric memory (MERAM)

摘要

Voltage controlled magnetic tunnel junctions and memory devices are described which provide efficient high speed switching of non-volatile magnetic devices at high cell densities. Implementations are described which provide a wide range of voltage control alternatives with in-plane and perpendicular magnetization, bidirectionally switched magnetization, and control of domain wall dynamics.

主权项

1. A voltage-controlled magneto-electric random access memory (MeRAM) apparatus, comprising:
at least three ferromagnetic (FM) layers having a FM fixed layer, a FM semi-fixed layer, and a FM free layer; wherein said FM semi-fixed layer and said FM free layer are disposed on opposite sides of said FM fixed layer; and a dielectric (DE) layer interposed between said FM free layer and FM fixed layer; a spacer layer separating said FM semi-fixed layer from said FM fixed layer; wherein material, shape and thickness of said FM free layer, said FM fixed layer, and said FM semi-fixed layer are selected to have in-plane (IP) and out-of-plane (OOP) anisotropies; wherein material, shape and thickness of said FM free layer is selected to have in-plane (IP) and out-of-plane (OOP) anisotropies which are nearly equal; wherein material, shape and thickness of said FM semi-fixed layer is selected to have in-plane (IP) and out-of-plane (OOP) anisotropies which are balanced between being nearly equal, and a preference plane of the FM fixed layer; wherein OOP anisotropy of said FM free layer is affected by the interface properties between the FM layers and said DE layer, and is controlled by voltages applied across said DE layer as an applied voltage, giving rise to a voltage-controlled magnetic anisotropy (VCMA) effect which rotates magnetization orientation of said FM free layer and is fully switched in response to a stray magnetic field from said FM semi-fixed and fixed layers, with state of the magnetic orientation determining bit state for said MeRAM; and wherein OOP anisotropy of said FM semi-fixed layer is affected by the interface properties between the FM layers and said DE layer, and is controlled by voltages applied across said DE layer as an applied voltage, giving rise to a voltage-controlled magnetic anisotropy (VCMA) effect which rotates magnetization orientation of said FM semi-fixed layer without fully switching its magnetic orientation.