Multibit self-reference thermally assisted MRAM
View Patent ↗A mechanism is provided for a thermally assisted magnetoresistive random access memory device (TAS-MRAM). A storage layer has an anisotropic axis, in which the storage layer is configured to store a state in off axis positions and on axis positions. The off axis positions are not aligned with the anisotropic axis. A tunnel barrier is disposed on top of the storage layer. A ferromagnetic sense layer is disposed on top of the tunnel barrier.
1. A method for writing data to a state in a thermally assisted magnetoresistive random access memory device (TAS-MRAM), the method comprising:
setting a magnetic orientation of a storage layer to a position for storing the state, wherein the storage layer has an anisotropic axis, and wherein the position of the magnetic orientation includes off axis positions and on axis positions relative to the anisotropic axis;
reading the state in the storage layer to obtain a first resistance value and a second resistance value of the storage layer;
comparing the first resistance value and the second resistance value to predetermined resistance values of the storage layer;
when the first resistance value and the second resistance value are different from the predetermined resistance values during the setting of magnetic orientation of the storage layer to the position for storing the state, resetting the magnetic orientation of the storage layer to the position for storing the state so that the first resistance value and the second resistance value are within a tolerance of the predetermined resistance values;
when the first resistance value and the second resistance value match the predetermined resistance values within the tolerance in response to the resetting to the position, verifying that the predetermined resistance values have been met by the first resistance value and the second resistance value, and subsequently storing the state.
2. The method of claim 1 , wherein reading the state in the storage layer to obtain the first resistance value includes measuring a resistance of the storage layer relative to a first magnetic orientation of a ferromagnetic sense layer in order to obtain the first resistance value.
3. The method of claim 2 , further comprising switching the first magnetic orientation of the ferromagnetic sense layer to a second magnetic orientation opposite the first magnetic orientation;
wherein reading the state in the storage layer to obtain the second resistance value includes measuring the resistance of the storage layer relative to the second magnetic orientation of the ferromagnetic sense layer in order to obtain the second resistance value.
4. The method of claim 1 , wherein the off axis positions define the magnetic orientation of the storage layer to be aligned off the anisotropic axis of the storage layer.
5. The method of claim 1 , wherein the magnetic orientation of the storage layer is aligned off the anisotropic axis by a range between 1 to 179 degrees.