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US 7,764,454 B2Granted
Exchange-bias based multi-state magnetic memory and logic devices and magnetically stabilized magnetic storage
AssigneeThe Regents of the University of California
InventorsIgor V. Roshchin, Oleg Petracic, Rafael Morales, Zhi-Pan Li, Xavier Batlle, Ivan K. Schuller
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Abstract
Magnetic materials and methods for using ferromagnetic and antiferromagnetic coupling and exchange bias for binary and multistate magnetic memory device.
Claims41
A device comprising:
- a magnetic storage material which comprises a ferromagnetic layer and an adjacent antiferromagnetic layer that are magnetically coupled to each other to store data in the ferromagnetic layer at an operating temperature which is lower than a blocking temperature of the antiferromagnetic layer,
- wherein the blocking temperature is lower than a Curie temperature of the ferromagnetic material,
- wherein the ferromagnetic layer and the antiferromagnetic layer are selected to offset a magnetic hysteresis loop of the magnetic storage material away from a zero field to a magnetic field greater than a stray magnetic field in the device;
- and
- a control mechanism to locally control a temperature and a magnetic field in a region of a selected magnetic domain and the magnetic storage material when data is written into the selected magnetic domain.
2 more elements
A device comprising:
- a magnetic storage material which comprises a ferromagnetic layer and an adjacent antiferromagnetic layer that are magnetically coupled to each other to store data at an operating temperature which is lower than a blocking temperature of the antiferromagnetic layer,
- wherein the blocking temperature is lower than a Curie temperature of the ferromagnetic material,
- wherein each of magnetic bits in the magnetic storage material is configured to have two or more domains of opposite directions of an exchange bias to constitute a multi-state storage medium comprising more than two magnetic states;
- and
- a control mechanism to locally control a temperature and a magnetic field in a region of a selected magnetic bit and the magnetic storage material when data is written into the selected magnetic bit.
2 more elements
A method for providing more than two magnetic states in each magnetic bit of a magnetic storage material, the method comprising:
- providing a magnetic storage material which comprises a ferromagnetic layer and an adjacent antiferromagnetic layer that are magnetically coupled to each other to store data at an operating temperature which is lower than a blocking temperature of the antiferromagnetic layer, wherein the blocking temperature is lower than a Curie temperature of the ferromagnetic material, and wherein each of magnetic bits in the material is formed by two domains of opposite directions of an exchange bias to constitute a multi-state storage medium comprising more than two magnetic states;
- performing localized heating to raise temperature of a selected magnetic bit having two domains of opposite directions of the exchange bias in the material above the blocking temperature;
- at the temperature above the blocking temperature, applying a magnetization process to the selected magnetic bit to set a remanent magnetization to a selected value of a pre-determined set of remanent magnetizations for the multi-state storage medium to write a bit;
- removing the external magnetic field at the selected magnetic bit;
- and
- at the zero field, reducing the temperature of the selected magnetic bit below the blocking temperature to store the remanent magnetization in the selected bit.
3 more elements
A method for providing more than two magnetic states in each magnetic bit of a magnetic storage material, the method comprising:
- providing a magnetic storage material which comprises a ferromagnetic layer and an adjacent antiferromagnetic layer that are magnetically coupled to each other to store data at an operating temperature which is lower than a blocking temperature of the antiferromagnetic layer, wherein the blocking temperature is lower than a Curie temperature of the ferromagnetic material, and wherein each of magnetic bits in the material is formed by two domains of opposite directions of an exchange bias to constitute a multi-state storage medium comprising more than two magnetic states;
- performing localized heating to raise temperature of a selected magnetic bit in the material above the blocking temperature;
- at the temperature above the blocking temperature, applying a magnetization process to the selected magnetic bit having two domains of opposite directions of the exchange bias to set a remanent magnetization to a selected value of a pre-determined set of remanent magnetizations for the multi-state storage medium to write a bit;
- while maintaining a magnetic field of the magnetization process, reducing the temperature of the selected magnetic bit below the blocking temperature to store the remanent magnetization in the selected bit.
1 more element
A method comprising:
- providing a magnetic storage material which comprises a ferromagnetic layer and an adjacent antiferromagnetic layer that are magnetically coupled to each other to provide a magnetic hysteresis loop as a binary-state magnetic storage medium;
- storing information in the ferromagnetic layer of the magnetic storage material;
- and
- configuring the ferromagnetic layer and the adjacent antiferromagnetic layer to set the center of the magnetic hysteresis loop in a coordinate formed by a magnetic field as the horizontal axis and a magnetization as the vertical axis to be away from a position along the horizontal axis where the magnetic field is zero (H =0) by an amount greater than a stray magnetic field to stabilize each stored binary-state against a change of magnetization caused by the stray magnetic field.
1 more element
A method comprising:
- providing a magnetic storage material which comprises a ferromagnetic layer and an adjacent antiferromagnetic layer that are magnetically coupled to each other to provide a magnetic hysteresis loop as a binary-state magnetic storage medium;
- storing information in the ferromagnetic layer of the magnetic storage material;
- and
- configuring the ferromagnetic layer and the adjacent antiferromagnetic layer to enhance uniaxial anisotropy of the ferromagnetic layer and increase a squareness of the magnetic hysteresis loop to stabilize each stored binary-state against a change of magnetization caused by a stray magnetic field, wherein the squareness of the magnetic hysteresis loop comprises a ratio of remanent and saturated magnetizations.
1 more element
A device comprising:
- a magnetic storage material which comprises a ferromagnetic layer and an adjacent antiferromagnetic layer that are magnetically coupled to each other to store data in the ferromagnetic layer at an operating temperature which is lower than a blocking temperature of the antiferromagnetic layer,
- wherein the blocking temperature is lower than a Curie temperature of the ferromagnetic material,
- wherein the ferromagnetic layer and the antiferromagnetic layer are selected to enhance uniaxial anisotropy of the ferromagnetic layer and increase a squareness of the magnetic hysteresis loop of the magnetic storage material,
- wherein the squareness of the magnetic hysteresis loop comprises a ratio of remanent and saturated magnetizations, and
- wherein a width of the magnetic hysteresis loop that has increased squareness corresponds to a field greater than a stray magnetic field in the device;
- and
- a control mechanism to locally control a temperature and a magnetic field in a region of a selected magnetic domain and the magnetic storage material when data is written into the selected magnetic domain.
4 more elements
Dependencies are inferred from the claim text.