Logic element using spin-orbit torque and magnetic tunnel junction structure
Disclosed is logic device using spin orbit torque. Two magnetic tunnel junctions have mutually opposite magnetization directions. The direction of the current flowing through the non-magnetic metal layer acts as an input, and the resistance states of the magnetic tunnel junctions are determined by the input program currents. Various logic devices are implemented by a method of setting the input program current to a logic high or a logic low.
1. A logic device comprising:
a non-magnetic metal layer through which a program current for generating spin orbital torque flows and output voltage is received, and having cross shape;
a lower magnetic part formed on the non-magnetic metal layer and having perpendicular magnetic anisotropy set by the program current, and being placed in straight line along two opposite ends of four ends of the cross shape; and
an upper magnetic part formed on the lower magnetic part and having at least two pinned magnetization units that are spaced apart from each other and face each other,
wherein the lower magnetic part comprises:
a common free layer formed on the non-magnetic metal layer and having a magnetization direction set by the program current, and
a common tunnel junction layer formed on the common free layer.
2. The logic device of claim 1 , wherein the non-magnetic metal layer having the cross shape comprises:
a first terminal formed on one end;
a second terminal opposite the first terminal;
a third terminal disposed at a position perpendicular to an imaginary line connecting the first terminal and the second terminal; and
a fourth terminal opposite to the third terminal,
wherein the lower magnetic part is formed on the first terminal and the second terminal.
3. The logic device of claim 2 , wherein the upper magnetic part comprises:
a first pinned magnetization unit formed on the common tunnel junction layer; and
a second pinned magnetization unit formed on the common tunnel junction layer and facing the first pinned magnetization unit,
wherein the first pinned magnetization unit and the second pinned magnetization unit have pinned magnetization states of opposite direction on the cross shape to each other.
4. The logic device of claim 3 , further comprising:
a first electrode formed on the first pinned magnetization unit; and
a second electrode formed on the second pinned magnetization unit,
wherein resistance of path composed of the first electrode, the first pinned magnetization unit, the common tunnel junction layer, the common free layer, the common tunnel junction layer, the second pinned magnetization unit and the second electrode is determined by the program current flowing between the first terminal and the second terminal, and the output voltage is received through the fourth terminal.
5. The logic device of claim 3 , wherein the first pinned magnetization unit comprises:
a first pinned layer formed on the common tunnel junction layer; and
a first magnetization inducing unit formed on the first pinned layer and configured to set magnetization state of the first pinned layer.
6. The logic device of claim 5 , wherein the first magnetization inducing unit has antiferromagnetic coupling and ferromagnetic coupling, and changes the magnetization state of the first pinned layer according to external magnetic field.
7. The logic device of claim 5 , wherein a magnetic moment due to antiferromagnetic coupling is greater than a magnetic moment due to ferromagnetic coupling.
8. The logic device of claim 5 , wherein the first magnetization inducing unit comprises:
a first ferromagnetic coupling inducing layer formed on the first pinned layer and to induce ferromagnetic coupling according to a Ruderman-Kittel-Kasuya-Yosida RKKY) interaction;
a first intermediate ferromagnetic layer formed on the first ferromagnetic coupling inducing layer and forming a ferromagnetic coupling with the first pinned layer;
a first antiferromagnetic coupling inducing layer formed on the first intermediate ferromagnetic layer and for inducing antiferromagnetic coupling according to the RKKY interaction; and
a first upper ferromagnetic layer formed on the first antiferromagnetic coupling inducing layer, forming an antiferromagnetic coupling with the first intermediate ferromagnetic layer, and having a thickness greater than that of the first intermediate ferromagnetic layer.
9. The logic device of claim 8 , wherein a magnetic moment due to antiferromagnetic coupling is greater than a magnetic moment due to ferromagnetic coupling.
10. The logic device of claim 5 , wherein the second pinned magnetization unit comprises:
a second pinned layer formed on the common tunnel junction layer; and
a second magnetization inducing unit formed on the second pinned layer and configured to set magnetization state of the second pinned layer,
wherein a magnetization direction of the second pinned layer is opposite to a magnetization direction of the first pinned layer.
11. The logic device of claim 10 , wherein the second pinned magnetization unit comprises:
a second ferromagnetic coupling inducing layer formed on the second pinned layer and to induce ferromagnetic coupling according to a Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction;
a second intermediate ferromagnetic layer formed on the second ferromagnetic coupling inducing layer and forming a ferromagnetic coupling with the first pinned layer;
a second antiferromagnetic coupling inducing layer formed on the second intermediate ferromagnetic layer and to induce antiferromagnetic coupling according to the RKKY interaction; and
a second upper ferromagnetic layer formed on the second antiferromagnetic coupling inducing layer and forming an antiferromagnetic coupling with the second intermediate ferromagnetic layer,
wherein a magnetic moment due to the ferromagnetic coupling is greater than a magnetic moment due to the antiferromagnetic coupling.