Magnetic laminated film, magnetic memory element, magnetic memory, and artificial intelligence system
A magnetic multilayer film for a magnetic memory element includes an amorphous heavy metal layer having a multilayer structure in which a plurality of first layers containing Hf alternate repeatedly with a plurality of second layers containing a heavy metal excluding Hf; and a recording layer that includes a ferromagnetic layer and that is adjacent to the heavy metal layer, the ferromagnetic layer having a variable magnetization direction.
1. A magnetic multilayer film for a magnetic memory element, the magnetic multilayer film comprising:
an amorphous heavy metal layer having a multilayer structure in which a plurality of first layers containing Hf alternate repeatedly with a plurality of second layers containing a heavy metal excluding Hf; and
a recording layer that includes a ferromagnetic layer and that is formed on the amorphous heavy metal layer, the ferromagnetic layer having a variable magnetization direction.
2. The magnetic multilayer film according to claim 1 , wherein each of the second layers contains W or a W alloy.
3. The magnetic multilayer film according to claim 1 , wherein each of the second layers contains one or more elements selected from among Co, Fe, and B.
4. The magnetic multilayer film according to claim 1 , wherein a layer of the amorphous heavy metal layer that is closest to the recording layer is one of the first layers.
5. The magnetic multilayer film according to claim 1 , wherein a thickness of the amorphous heavy metal layer is in a range from 1.4 nm to 9 nm.
6. A magnetic memory element, comprising:
the magnetic multilayer film according to claim 1 ;
a barrier layer that is formed on the recording layer and that is made of an insulator; and
a reference layer that is formed on the barrier layer, the reference layer having a fixed magnetization direction, wherein
the magnetization direction of the ferromagnetic layer of the recording layer is reversible by a write current passing through the amorphous heavy metal layer.
7. The magnetic memory element according to claim 6 , further comprising:
a first terminal provided on a first end of the amorphous heavy metal layer in a lengthwise direction thereof, and that supplies the write current to the amorphous heavy metal layer;
a second terminal provided on a second end of the amorphous heavy metal layer in the lengthwise direction thereof opposite to the first end of the amorphous heavy metal layer, and that supplies the write current to the amorphous heavy metal layer; and
a third terminal electrically connected to the reference layer, wherein
the write current passes between the first terminal and the second terminal via the amorphous heavy metal layer.
8. The magnetic memory element according to claim 6 , wherein the magnetization direction of the ferromagnetic layer of the recording layer is perpendicular to a surface of the ferromagnetic layer.
9. A magnetic memory, comprising:
the magnetic memory element according to claim 6 ,
a writing circuit that includes a writing source for writing data to the magnetic memory element by passing the write current through the amorphous heavy metal layer; and
a reading circuit that includes a read-out source for passing a read-out current through the barrier layer, and a current detector that detects the read-out current passing through the barrier layer and that reads the data written to the magnetic memory element.
10. The magnetic memory according to claim 9 , wherein a laminate including the recording layer, the barrier layer, and the reference layer, as seen from a side opposite to the amorphous heavy metal layer, is asymmetrical in relation to a direction along the write current.
11. An artificial intelligence system, wherein the magnetic memory element according to claim 6 is used as an electronic neuron to which a weighted sum of a resistive crossbar network is inputted.
12. The artificial intelligence system according to claim 11 , wherein the magnetic memory element is additionally used as a cross-point memory of the resistive crossbar network.
13. The artificial intelligence system according to claim 11 , wherein a laminate including the recording layer, the barrier layer, and the reference layer, as seen from a side opposite to the amorphous heavy metal layer, has line symmetry in relation to a direction along the write current.