Magnetic memory element utilizing spin transfer switching and storing multiple bits

A magnetic element capable of storing multiple bits comprising:

• a first dual spin tunnel/valve structure including a first pinned layer, a first nonmagnetic spacer layer, a first free layer, a first barrier layer, and a second pinned layer, the first nonmagnetic spacer layer residing between the first pinned layer and the first free layer, the first barrier layer residing between the first free layer and the second pinned layer;
• a connecting layer;
• and
• a second dual spin tunnel/valve structure including a third pinned layer, a second nonmagnetic spacer layer, a second free layer, a second barrier layer, and a fourth pinned layer, the second nonmagnetic spacer layer residing between the third pinned layer and the second free layer, the second barrier layer residing between the second free layer and the fourth pinned layer;
• wherein the first dual spin tunnel/valve structure is configured to be written using a first write current having a first magnitude and a second write current having a second magnitude, the first write current in a first current direction, the second current in a second current direction and wherein the second dual spin tunnel/valve structure is configured to be written using a third current write current having a third magnitude and a fourth write current having a fourth magnitude, the third write current in the first current direction, the fourth write current in the second direction, the first magnitude being different from the third magnitude, the second magnitude being different the fourth magnitude.

A method for programming a magnetic element capable of storing multiple bits comprising the steps of:

• if a first state is to be written, passing a first current through the magnetic element, the magnetic element including a first pinned layer, a first nonmagnetic layer, a first free layer, a connecting layer, a second pinned layer, a second nonmagnetic layer, and a second free layer, the first pinned layer being ferromagnetic and having a first pinned layer magnetization, the first pinned layer magnetization being pinned in a first direction, the first nonmagnetic layer residing between the first pinned layer and the first free layer, the first free layer being ferromagnetic and having a first free layer magnetization, the second pinned layer being ferromagnetic and having a second pinned layer magnetization pinned in a second direction, the connecting layer residing between the second pinned layer and the first free layer, the second nonmagnetic layer residing between the second pinned layer and the second free layer, the second free layer being ferromagnetic and having a second free layer magnetization, the magnetic element being configured to allow the first free layer magnetization and the second free layer magnetization to change direction due to spin transfer, the first current being sufficient to align the first free layer magnetization parallel to the first pinned layer magnetization and to align the second free layer magnetization parallel to the second pinned layer magnetization;
• applying at least a second current through the magnetic element, the at least the second current leaves the first free layer magnetization parallel to the first pinned layer magnetization and aligning the second free layer magnetization antiparallel to the second pinned layer magnetization;
• if a third state is to be written, applying at least a third current through the magnetic element, the at least the third current aligning the first free layer magnetization antiparallel to the first pinned layer magnetization and aligning the second free layer magnetization antiparallel to the second pinned layer magnetization;
• and
• if a fourth state is to be written, after applying the first current, applying at least a fourth current through the magnetic element, the at least the fourth current leaves the first free layer magnetization antiparallel to the first pinned layer magnetization and aligning the second free layer magnetization parallel to the second pinned layer magnetization.

A method for providing magnetic element capable of storing multiple bits comprising the steps of:

• providing a first pinned layer, the first pinned layer being ferromagnetic and having a first pinned layer magnetization, the first pinned layer magnetization being pinned in a first direction;
• providing a first nonmagnetic layer;
• providing a first free layer, the first nonmagnetic layer residing between the first pinned layer and the first free layer, the first free layer being ferromagnetic and having a first free layer magnetization;
• providing a connecting layer;
• providing a second pinned layer, the second pinned layer being ferromagnetic and having a second pinned layer magnetization pinned in a second direction, the connecting layer residing between the second pinned layer and the first free layer;
• providing a second nonmagnetic layer;
• providing a second free layer, the second nonmagnetic layer residing between the second pinned layer and the second free layer, the second free layer being ferromagnetic and having a second free layer magnetization;
• wherein the magnetic element is configured to allow the first free layer magnetization and the second free layer magnetization to change direction due to spin transfer when a write current is passed through the magnetic element;
• wherein the first free layer is configured to be written using a first write current having a first magnitude and a second write current having a second magnitude, the first write current in a first current direction, the second current in a second current direction and wherein the second free layer is configured to be written using a third current write current having a third magnitude and a fourth write current having a fourth magnitude, the third write current in the first current direction, the fourth write current in the second direction, the first magnitude being different from the third magnitude, the second magnitude being different the fourth magnitude.

A method for providing a magnetic element capable of storing multiple bits comprising the steps of:

• providing a first dual spin tunnel/valve structure including a first pinned layer, a first nonmagnetic spacer layer, a first free layer, a first barrier layer, and a second pinned layer, the first nonmagnetic spacer layer residing between the first pinned layer and the first free layer, the first barrier layer residing between the first free layer and the second pinned layer;
• providing a connecting layer;
• and
• providing a second dual spin tunnel/valve structure including a third pinned layer, a second nonmagnetic spacer layer, a second free layer, a second barrier layer, and a fourth pinned layer, the second nonmagnetic spacer layer residing between the third pinned layer and the second free layer, the second barrier layer residing between the second free layer and the fourth pinned layer;
• wherein the first dual spin tunnel/valve structure is configured to be written using a first write current having a first magnitude and a second write current having a second magnitude, the first write current in a first current direction, the second current in a second current direction and wherein the second dual spin tunnel/valve structure is configured to be written using a third current write current having a third magnitude and a fourth write current having a fourth magnitude, the third write current in the first current direction, the fourth write current in the second direction, the first magnitude being different from the third magnitude, the second magnitude being different the fourth magnitude.