Self-referenced magnetic random access memory element comprising a synthetic storage layer
View Patent ↗The present disclosure concerns a MRAM element comprising a magnetic tunnel junction comprising: a storage layer, a sense layer, and a tunnel barrier layer included between the storage layer and the sense layer; the storage layer comprising a first magnetic layer having a first storage magnetization; a second magnetic layer having a second storage magnetization; and a non-magnetic coupling layer separating the first and second magnetic layers such that the first storage magnetization is substantially antiparallel to the second storage magnetization; the first and second magnetic layers being arranged such that: at a read temperature the first storage magnetization is substantially equal to the second storage magnetization; and at a write temperature which is higher than the read temperature the second storage magnetization is larger than the first storage magnetization. The disclosed MRAM element generates a low stray field when the magnetic tunnel junction is cooled at a low temperature.
1. A random access memory (MRAM) element comprising a magnetic tunnel junction comprising: a storage layer; a sense layer; and a tunnel barrier layer included between the storage layer and the sense layer; the storage layer comprising:
a first magnetic layer having a first storage magnetization;
a second magnetic layer having a second storage magnetization; and
a non-magnetic coupling layer separating the first and second magnetic layers such that the first storage magnetization is substantially antiparallel to the second storage magnetization; the first and second magnetic layers being arranged such that:
at a read temperature the first storage magnetization is substantially equal to the second storage magnetization; and
at a write temperature which is higher than the read temperature the second storage magnetization is larger than the first storage magnetization.
2. MRAM element according to claim 1 , wherein
the first magnetic layer comprises a first ferromagnetic layer having a first Curie temperature, and the second magnetic layer comprises a second ferromagnetic layer having a second Curie temperature which is higher than the first Curie temperature.
3. MRAM element according to claim 2 , wherein
the write temperature is comprised below the first and second Curie temperatures.
4. MRAM element according to claim 2 , wherein
the write temperature is comprised above the first Curie temperature and below the second Curie temperature.
5. MRAM element according to claim 1 , wherein
the first magnetic storage layer comprises a ferrimagnetic amorphous alloy comprising a sub-lattice of transition metals atoms providing a 3d storage magnetization, and a sub-lattice of rare-earth atoms providing a 4f storage magnetization being antiparallel to the 3d storage magnetization; and wherein
the first storage magnetization corresponds to the vectorial sum of the 3d storage magnetization and the 4f storage magnetization.
6. MRAM element according to claim 5 , wherein
the rare-earth sub-lattice has a first Curie temperature and the transition metal atom sub-lattice has a second Curie temperature which is higher than the first Curie temperature.
7. MRAM element according to claim 6 , wherein
the write temperature corresponds substantially to a compensation temperature of the ferrimagnetic storage layer, where the first storage magnetization becomes substantially zero.
8. MRAM element according to claim 6 , wherein
the write temperature corresponds substantially to the first Curie temperature of the rare-earth sub-lattice of the ferrimagnetic storage layer.
9. A method for writing a MRAM element comprising a magnetic tunnel junction including a storage layer, a sense layer, and a tunnel barrier layer between the storage layer and the sense layer; the storage layer comprising a first magnetic layer having a first storage magnetization, a second magnetic layer having a second storage magnetization, and a non-magnetic coupling layer separating the first and second magnetic layers such that the first storage magnetization is substantially antiparallel to the second storage magnetization; the first and second magnetic layers being arranged such that at a read temperature the first storage magnetization is substantially equal to the second storage magnetization, and at a write temperature which is higher than the read temperature the second storage magnetization is larger than the first storage magnetization; the method comprising:
heating the magnetic tunnel junction at the write temperature;
adjusting the first and second storage magnetizations; and
cooling the magnetic tunnel junction at the read temperature.
10. Method according to claim 9 , wherein
adjusting the first and second storage magnetizations is performed by applying a write magnetic field.
11. Method according to claim 9 , wherein
the MRAM element further comprises a current line in electrical contact with one end of the magnetic tunnel junction; and wherein
heating the magnetic tunnel junction comprises passing a heating current in the magnetic tunnel junction via the current line.