Perpendicular shape anisotropy design with asymmetric composite free layer

1 . A memory device, comprising:

a magnetic tunnel junction (MTJ) structure comprising perpendicular shape anisotropy, and the MTJ structure further comprising:

a reference layer comprising a first side and a second side that is opposite the first side of the reference layer;

a non-magnetic spacer comprising a first side and a second side, the first side of the non-magnetic spacer being on the second side of the reference layer and the second side of the non-magnetic spacer being opposite the first side of the non-magnetic spacer; and

free layer comprising a first side and a second side, the first side of the free layer being on the second side of the non-magnetic spacer and the second side of the free layer being opposite the first side of the free layer, the free layer further comprising a first layer on the first side of the free layer, a second layer on the second side of the free layer and a coupling layer disposed between the first layer and the second layer, a saturation magnetization MsFL 2 of the second layer being between 2 and 5 times inclusive a saturation magnetization MsFL 1 of the first layer.

2 . The memory device of claim 1 , wherein the first layer is easier to switch magnetization directions than the second layer.

3 . The memory device of claim 1 , wherein a ratio of thickness of the first layer to a thickness of the first layer and the second layer is less than 0.5.

4 . The memory device of claim 1 , wherein:

a ratio of a thickness of the free layer to a critical dimension of the MTJ structure is between 0.5 and 5.0 inclusive, and

the critical dimension of the MTJ structure ranges from 4 nanometers (nm) to 22 nm inclusive.

5 . The memory device of claim 1 , wherein the first layer comprises CoFeX or CoFeBX in which X is a diluent element comprising vanadium (V), molybdenum (Mo), titanium (Ti), zirconium (Zr), hafnium (Hf), aluminum (Al), niobium (Nb), tantalum (Ta), chromium (Cr), rhodium (Rh) or bismuth (Bi), and

wherein the second layer comprises CoFe or CoFeB.

6 . The memory device of claim 1 , wherein the coupling layer comprises a coupling of 0.5 erg per square centimeter (erg/cm2) to 3.0 erg/cm2.

7 . The memory device of claim 1 , wherein the non-magnetic spacer comprises a metallic spacer, and

wherein one of the first layer or the second layer comprises a Heusler material.

8 . The memory device of claim 1 , further comprising a spin-orbit torque (SOT) line on the second side of the free layer, the SOT line comprising alloys of two or more of tungsten (W), platinum (Pt), terbium (Tb), bismuth (Bi), selenium (Se), hafnium (Hf), zirconium (Zr), silver (Ag), gold (Au), and silicon (Si) materials.

9 . A memory device, comprising:

a magnetic tunnel junction (MTJ) structure comprising perpendicular shape anisotropy, and the MTJ structure further comprising:

a reference layer comprising a first side and a second side that is opposite the first side of the reference layer;

a non-magnetic spacer comprising a first side and a second side, the first side of the non-magnetic spacer being on the second side of the reference layer and the second side of the non-magnetic spacer being opposite the first side of the non-magnetic spacer; and

free layer comprising a first side and a second side, the first side of the free layer being on the second side of the non-magnetic spacer and the second side of the free layer being opposite the first side of the free layer, the free layer further comprising a first layer on the first side of the free layer, a second layer on the second side of the free layer and a coupling layer disposed between the first layer and the second layer, a ratio of thickness of the first layer to a thickness of the first layer and the second layer is less than 0.5, wherein a ratio of a thickness of the free layer to an in-plane lateral dimension of the MTJ structure ranges between a first value and a second value.

10 . The memory device of claim 9 , wherein the first layer is easier to switch magnetization directions than the second layer.

11 . The memory device of claim 9 , wherein a saturation magnetization MsFL 2 of the second layer being between 2 and 5 times a saturation magnetization MsFL 1 of the first layer.

12 . The memory device of claim 9 , wherein:

the ratio of the thickness of the free layer to the in-plane lateral dimension of the MTJ structure is between 0.5 and 5.0 inclusive, and

the in-plane lateral dimension of the MTJ structure ranges from 4 nanometers (nm) to 22 nm inclusive.

13 . The memory device of claim 9 , wherein the first layer comprises CoFeX or CoFeBX in which X is a diluent element comprising vanadium (V), molybdenum (Mo), titanium (Ti), zirconium (Zr), hafnium (Hf), aluminum (Al), niobium (Nb), tantalum (Ta), chromium (Cr), rhodium (Rh) or bismuth (Bi), and

wherein the second layer comprises CoFe or CoFeB.

14 . The memory device of claim 9 , wherein the coupling layer comprises a coupling of 0.5 erg per square centimeter (erg/cm2) to 3.0 erg/cm2.

15 . The memory device of claim 9 , wherein the non-magnetic spacer comprises a metallic spacer, and

wherein one of the first layer or the second layer comprises a Heusler material.

16 . The memory device of claim 9 , further comprising a spin-orbit torque (SOT) line on the second side of the free layer, the SOT line comprising alloys of two or more of tungsten (W), platinum (Pt), terbium (Tb), bismuth (Bi), hafnium (Hf), selenium (Se), zirconium (Zr), silver (Ag), gold (Au), and silicon (Si) materials.

17 . A memory device, comprising:

a magnetic tunnel junction (MTJ) structure comprising perpendicular shape anisotropy, and the MTJ structure further comprising:

a reference layer comprising a first side and a second side that is opposite the first side of the reference layer;

a non-magnetic spacer comprising a first side and a second side, the first side of the non-magnetic spacer being on the second side of the reference layer and the second side of the non-magnetic spacer being opposite the first side of the non-magnetic spacer, the non-magnetic spacer comprising a metallic spacer; and

a free layer comprising a first side and a second side, the first side of the free layer being on the second side of the non-magnetic spacer and the second side of the free layer being opposite the first side of the free layer, the free layer further comprising a first layer on the first side of the free layer, a second layer on the second side of the free layer and a coupling layer disposed between the first layer and the second layer, one of the first layer or the second layer comprises a Heusler material, and a saturation magnetization MsFL 2 of the second layer being between 2 and 5 times inclusive of a saturation magnetization MsFL 1 of the first layer.

18 . The memory device of claim 17 , wherein the coupling layer comprises a coupling of 0.5 erg per square centimeter (erg/cm2) to 3.0 erg/cm2 inclusive.

19 . The memory device of claim 17 , wherein:

the first layer is easier to switch magnetization directions than the second layer,

a ratio of a thickness of the free layer to a critical dimension of the MTJ structure is between 0.5 and 5.0 inclusive, and

the critical dimension of the MTJ structure ranges from 4 nanometers (nm) to 22 nm.

20 . The memory device of claim 17 , further comprising a capping layer on the second side of the free layer comprising one or more of magnesium oxide (MgO), tantalum oxide (TaO), niobium oxide (NiO), iridium oxide (IrO), sodium oxide (NaO), rhodium oxide (RhO), or osmium oxide (OsO).