High Density Magnetic Random Access Memory

A magnetic memory device comprising:

• a substrate;
• a first plurality of electrically conductive lines formed on the substrate;
• a second plurality of electrically conductive lines formed on the substrate and overlapping the first plurality of lines at a plurality of intersection regions;
• a plurality of memory cells formed on the substrate and arranged in an array, each memory cell being located at an intersection region and comprising a magnetic tunnel junction which includes a free ferromagnetic layer having a reversible magnetization direction directed substantially perpendicular to the substrate in an equilibrium state, a pinned ferromagnetic layer having a fixed magnetization direction, and an insulating tunnel layer disposed between the pinned ferromagnetic layer and the free ferromagnetic layer, each magnetic tunnel junction is electrically coupled to one of the first plurality of lines at the free ferromagnetic layer and to one of the second plurality of lines at the pinned ferromagnetic layer,
• wherein the magnetization direction of the free ferromagnetic layer is reversed by a spin-polarized current flowing through the magnetic tunnel junction in a direction perpendicular to the substrate.

A method for writing to a magnetic memory device comprising a plurality of magnetic tunnel junctions formed on a substrate and arranged in columns and rows, each magnetic tunnel junction comprising a free ferromagnetic layer having a reversible magnetization direction directed substantially perpendicular to the substrate in an equilibrium state, a pinned ferromagnetic layer having a fixed magnetization direction, and an insulating tunnel barrier layer disposed between the free ferromagnetic layer and the pinned ferromagnetic layer, the method comprising:

• applying a bias current to a bit conductive line comprising ferromagnetic cladding and being electrically coupled to a row of magnetic tunnel junctions at the free ferromagnetic layer to produce a bias magnetic field along a hard magnetic axis of the free ferromagnetic layer;
• applying a first current to a conductive word line electrically coupled to a column of magnetic tunnel junctions at the pinned ferromagnetic layer to produce a spin momentum transfer in the free ferromagnetic layer of a magnetic tunnel junction located at a first intersection region of the bit conductive line and the word conductive line,
• wherein the bias current and the first current are applied at the same time, and a joint effect of the bias magnetic field and the spin momentum transfer causes a reversal of the magnetization direction of the free ferromagnetic layer of the magnetic tunnel junction located at the first intersection region.