Thermal spin torque transfer magnetoresistive random access memory
View Patent ↗A thermal spin torque transfer magnetoresistive random access memory (MRAM) apparatus includes a magnetic tunnel junction and a tunnel junction programming circuit. The magnetic tunnel junction includes a reference layer having a fixed magnetic polarity, a tunnel barrier layer, and a free layer on an opposite side of the tunnel barrier layer from the reference layer. The free layer includes a first layer having a first Curie temperature and a second layer having a second Curie temperature different from the first Curie temperature. The tunnel junction programming circuit is configured to apply a current through the magnetic tunnel junction to generate a write temperature in the magnetic tunnel junction and to write to the free layer of the magnetic tunnel junction.
1. A method of writing to a tunnel junction of a thermal spin torque transfer magnetoresistive random access memory (MRAM) apparatus, the thermal spin torque transfer MRAM apparatus including a magnetic tunnel junction having a reference layer, a tunnel barrier layer, and a free layer, the free layer comprising a first layer having a first Curie temperature and a second layer having a second Curie temperature, the method comprising:
applying a write current to the magnetic tunnel junction to heat the magnetic tunnel junction to a write temperature less than the first Curie temperature and greater than the second Curie temperature.
2. The method of claim 1 , wherein the write current is applied to the magnetic tunnel junction based on determining that a tunnel junction control signal corresponds to a write operation, the method further comprising:
applying a read current to the magnetic tunnel junction to heat the magnetic tunnel junction to a read temperature less than each of the first Curie temperature and the second Curie temperature.
3. The method of claim 1 , wherein the first Curie temperature is greater than 150 degrees Celsius (°C.) and the second Curie temperature is less than 200° C.
4. The method of claim 1 , wherein the first and second layers have a combined thermal stability corresponding to a target magnetic polarization retention capability at a predetermined non-write operating temperature.
5. The method of claim 1 , wherein the first layer has a magnetic energy between around 10 k B T and around 20 k B T, wherein k B is the Boltzmann constant and T is an ambient temperature.
6. The method of claim 1 , wherein the magnetic tunnel junction further comprises a non-magnetic spacer between the first layer and the second layer.