Magnetic memory element

Abstract

This magnetic memory element comprises: a fixed layer in which a magnetization direction is fixed; a free layer in which a magnetization direction can be reversed; and a barrier layer which is provided between the fixed layer and the free layer so as to obtain a tunnel magnetoresistance (TMR) effect. The magnetization of the free layer is reversed by a voltage-controlled magnetic anisotropy (VCMA) effect by means of voltage application. The barrier layer contains MgO and at least one of Fe, Co, Mn, V, and Ti.

Description

Magnetic memory element

[0001] This disclosure relates to a magnetic memory element.

[0002] In magnetic memory elements, data is written by reversing the magnetization of the free layer (see, for example, Patent Document 1).

[0003] International Publication No. 2018 / 179961

[0004] Some voltage-driven magnetic memory elements use voltage magnetic anisotropy control (VCMA) to reverse the magnetization of the free layer. There is room for further investigation into improving VCMA efficiency.

[0005] One aspect of this disclosure is to improve VCMA efficiency.

[0006] A magnetic memory element relating to one aspect of this disclosure comprises a fixed layer with a fixed magnetization direction, a free layer whose magnetization direction can be reversed, and a barrier layer provided between the fixed layer and the free layer so as to obtain a tunnel magnetoresistance (TMR) effect, wherein the magnetization of the free layer is reversed by a voltage-induced magnetic anisotropy control (VCMA) effect, and the barrier layer comprises MgO and at least one of Fe, Co, Mn, V, and Ti.

[0007] This figure shows an example of the schematic configuration of the magnetic memory element 1 according to the embodiment. This figure shows an example of the schematic configuration of the barrier layer 5. This figure shows an example of the schematic configuration of the magnetic memory element 1. This figure shows an example of improving VCMA efficiency. This figure shows an example of suppressing the decrease in TMR ratio. This figure shows an example of the configuration of the barrier layer 5. This figure shows an example of an embodiment. This figure shows an example of an embodiment. This figure shows an example of an embodiment. This figure shows an example of the schematic configuration of the magnetic memory element 1. This figure shows an example of the design of the heavy metal layer 6. This figure shows an example of the design of the heavy metal layer 6. This figure shows an example and a modified example. This figure shows an example and a modified example. This figure shows an example and a modified example. This figure shows an example and a modified example. This figure shows an example and a modified example. This figure shows an example and a modified example. This figure shows an example and a modified example. This figure shows an example and a modified example. This figure shows an example and a modified example. This figure shows an example and a modified example. This figure shows an example and a modified example. This figure shows an example and a modified example. This figure shows an example and a modified example. This figure shows an example and a modified example. This figure shows an example and a modified example.

[0008] Embodiments of this disclosure will be described in detail below with reference to the drawings. In each of the following embodiments, the same elements will be denoted by the same reference numerals to avoid redundant descriptions.

[0009] This disclosure will be described in the following order of items: 1. Embodiments 2. Examples and Modifications 3. Summary

[0010] 1. Embodiment Figure 1 is a diagram showing an example of the schematic configuration of a magnetic memory element 1 according to an embodiment. The magnetic memory element 1 is a magnetic tunnel junction (MTJ) element and is configured to have a tunnel magnetoresistance (TMR) effect.

[0011] The magnetic memory element 1 includes a substrate 2, a fixed layer 3, a free layer 4, and a barrier layer 5. Note that the term "layer" may be interpreted to include films, and these terms may be appropriately replaced within a range that does not contradict each other.

[0012] The XYZ coordinate system is also shown. The X-axis and Y-axis directions (XY plane directions) correspond to the plane directions of the layers and substrate. The Z-axis direction corresponds to the thickness direction of the layers and substrate. The magnetic memory element 1 may be a bottom-pin type or a top-pin type.

[0013] Figure 1(A) illustrates a bottom-pin type magnetic memory element 1. The fixed layer 3 is located closer to the substrate 2 than the free layer 4, and is situated between the substrate 2 and the free layer 4. In this example, the substrate 2, fixed layer 3, barrier layer 5, and free layer 4 are positioned in this order in the positive Z-axis direction.

[0014] Figure 1(B) illustrates a top-pin type magnetic memory element 1. The free layer 4 is located closer to the substrate 2 than the fixed layer 3, and is situated between the substrate 2 and the fixed layer 3. In this example, the substrate 2, free layer 4, barrier layer 5, and fixed layer 3 are positioned in this order in the positive Z-axis direction.

[0015] In the following explanation, we will primarily assume that the magnetic memory element 1 is a bottom-pin type as shown in Figure 1(A).

[0016] The substrate 2 is a semiconductor substrate, such as a silicon (Si) substrate. Circuits for controlling the magnetic memory element 1 are formed on the substrate 2.

[0017] The fixed layer 3 is a pinned layer in which the direction of magnetization is fixed, and is also called a magnetization fixed layer. In the figure, the direction of magnetization of the fixed layer 3 is schematically shown by a white arrow. In this example, the direction of magnetization of the fixed layer 3 is fixed in the positive Z-axis direction (perpendicular direction). The fixed layer 3 is composed of a magnetic material and can also be called a magnetic layer. For example, the direction of magnetization of the fixed layer 3 is fixed by laminating a ferromagnetic layer such as CoFe or CoFeB, a laminated ferri-coupling layer having a laminated ferri-bonding via a spacer layer of Ru or Ir, and a hard magnetic layer containing CoPt or CoIr. Alternatively, the direction of magnetization is fixed by laminating an antiferromagnetic material such as IrMn or PtMn with a CoFe layer or CoFeB layer.

[0018] The free layer 4 is a layer whose magnetization direction can be reversed, and is also called a memory layer. In the figure, the magnetization direction of the free layer 4 is schematically shown by a white arrow. In this example, the magnetization direction of the free layer 4 can be reversed between the positive Z-axis direction and the negative Z-axis direction. The free layer 4 is composed of a magnetic material and can also be called a magnetic layer. For example, the free layer 4 may be a CoFe layer or a CoFeB layer.

[0019] Regarding the thickness of the free layer 4 (length in the Z-axis direction), an example of the lower limit of the thickness is 0.6 nm (nanometers). An example of the upper limit of the thickness is 1.5 nm. For example, the thickness of the free layer 4 may be between 0.6 nm and 1.5 nm. The thickness of the free layer 4 will be explained again later with reference to Figures 26 and 27.

[0020] The barrier layer 5 is provided between the fixed layer 3 and the free layer 4 to obtain the TMR effect. The barrier layer 5 is also called a tunnel barrier layer or tunnel barrier layer. The barrier layer 5 contains at least MgO.

[0021] In the magnetic memory element 1 according to this embodiment, the barrier layer 5 includes MgO and a predetermined material. Examples of the predetermined material are Fe, Co, Mn, V, and Ti, and at least one of these may be included in the barrier layer 5 as the predetermined material.

[0022] Hereafter, unless otherwise specified, the designated material of barrier layer 5 shall be Fe. Within the bounds of consistency, Fe in barrier layer 5 may be appropriately replaced with Co, Mn, V, Ti, etc.

[0023] Regarding the content of the specified material in the barrier layer 5, an example of the lower limit of the content is 5 at% (atomic percent). An example of the upper limit of the content is 10 at%. For example, the content of the specified material in the barrier layer 5 may be between 5 at% and 10 at%.

[0024] Regarding the thickness of the barrier layer 5, an example of a lower limit is 1.3 nm. An example of an upper limit is 3.0 nm. For example, the thickness of the barrier layer 5 may be between 1.3 nm and 3.0 nm. The thickness of the barrier layer 5 will be explained again later with reference to Figure 6.

[0025] The barrier layer 5 may have a laminated structure (multilayer structure) or a single-layer structure. This will be explained with reference to Figure 2.

[0026] Figure 2 shows an example of the schematic configuration of the barrier layer 5. In the examples shown in Figures 2(A) to (D), the barrier layer 5 has a laminated structure. Specifically, the barrier layer 5 includes two types of layers. The first layer is referred to as barrier layer 51 and is shown in the figure. The second layer is referred to as barrier layer 52 and is shown in the figure. Barrier layer 51 is a layer containing MgO and Fe, i.e., a FeMgO layer. Barrier layer 52 is a layer containing MgO, i.e., a MgO layer.

[0027] In the example shown in Figure 2(A), the barrier layer 5 includes barrier layer 52 and barrier layer 51 stacked sequentially in the positive Z-axis direction. In the example shown in Figure 2(B), the barrier layer 5 includes barrier layer 51 and barrier layer 52 stacked sequentially in the positive Z-axis direction.

[0028] In the example shown in Figure 2(C), the barrier layer 5 includes two barrier layers 51 and one barrier layer 52. The first of the two barrier layers 51 is referred to as barrier layer 51-1 and is shown in the figure. The second barrier layer is referred to as barrier layer 51-2 and is shown in the figure. Barrier layers 51-1 and 51-2 are located on opposite sides of each other with barrier layer 52 in between. The barrier layer 5 includes barrier layers 51-1, 52, and 51-2 stacked in order in the positive Z-axis direction.

[0029] In the example shown in Figure 2(D), the barrier layer 5 includes one barrier layer 51 and two barrier layers 52. The first of the two barrier layers 52 is referred to as barrier layer 52-1 and is shown in the figure. The second barrier layer is referred to as barrier layer 52-2 and is shown in the figure. Barrier layers 52-1 and 52-2 are located on opposite sides of each other with barrier layer 51 in between. The barrier layer 5 includes barrier layer 52-1, barrier layer 51 and barrier layer 52-2, which are stacked in order in the positive Z-axis direction.

[0030] In the example shown in Figure 2(E), the barrier layer 5 has a single-layer structure. The barrier layer 5 is the barrier layer 51.

[0031] Returning to Figure 1, various other layers (not shown) may be provided between the stationary layer 3 and the substrate 2. For example, a layer for fixing the magnetization direction of the stationary layer 3 may be provided, and this layer may be an SAF layer having a multilayer ferri structure, or it may be an antiferromagnetic layer. Below these magnetization-fixing layers that fix the magnetization of the stationary layer 3 (on the negative Z-axis side), a hard layer, and an underlayer for promoting the crystal orientation of the hard layer and the magnetization-fixing layer and improving the magnetic properties may also be provided, and materials containing Ta, Ru, Pt, Cr, Mo, or compounds and alloys thereof can be used as the underlayer. In addition, an electrode layer for routing current from the element to the circuit and a CMOS (complementary metal oxide semiconductor) circuit are formed.

[0032] In the magnetic memory element 1 having the configuration described above, the barrier layer 5 includes not only MgO but also a predetermined material (such as Fe). This makes it possible to improve the flatness and crystal orientation of the interface between the barrier layer 5 and the magnetic layer in contact with it, specifically the free layer 4, compared to the case where the barrier layer 5 contains only MgO (and does not contain the predetermined material). Consequently, the VCMA efficiency can be improved.

[0033] The magnetic memory element 1 according to the embodiment can efficiently reverse the magnetization of the free layer 4 by the VCMA effect caused by voltage application. That is, the magnetic memory element 1 can be suitably used as a VCMA type magnetic memory element. The VCMA type magnetic memory element referred to here is distinguished from, for example, a spin polarized current drive (STT) type magnetic memory element in that the anisotropy is controlled by voltage application and the magnetization is not reversed by flowing a current through the MTJ element.

[0034] <Addition of heavy metal layer> In order to further improve the VCMA efficiency, a heavy metal layer such as an Ir layer may be inserted between the barrier layer 5 and the free layer 4 (magnetic layer). This will be described with reference to FIG. 3.

[0035] FIG. 3 is a diagram showing an example of the schematic configuration of the magnetic memory element 1. The surface on the negative Z-axis side of the free layer 4 is referred to as surface 4b and is illustrated. The surface on the positive Z-axis side of the barrier layer 5 is referred to as surface 5a and is illustrated. The surface 4b of the free layer 4 and the surface 5a of the barrier layer 5 may correspond to the interface between the free layer 4 and the barrier layer 5.

[0036] The magnetic memory element 1 further includes a heavy metal layer 6. The heavy metal layer 6 is provided on the free layer 4. Here, "on the free layer 4" may be interpreted in either sense of the surface on the positive Z-axis side and the surface on the negative Z-axis side of the free layer 4, and in the example shown in FIG. 3, it means on the surface 4b of the free layer 4.

[0037] The heavy metal layer 6 is located between the free layer 4 and the barrier layer 5, and thus is inserted into the interface between the free layer 4 and the barrier layer 5. As the name implies, the heavy metal layer 6 contains a heavy metal material. Examples of the heavy metal material are Ir, Os, etc. The heavy metal layer 6 may be, for example, an Ir layer or an Os layer.

[0038] Regarding the thickness of the heavy metal layer 6, an example of the lower limit value of the thickness is 0.05 nm. An example of the upper limit value of the thickness is 0.25 nm. For example, the thickness of the heavy metal layer 6 may be 0.05 nm or more and 0.25 nm or less. The thickness of the heavy metal layer 6 will be described again later with reference to FIGS. 12 and 13.

[0039] Since the heavy metal layer 6 is inserted at the interface between the barrier layer 5 and the free layer 4 (magnetic layer), the VCMA efficiency is further improved. However, the MgO contained in the barrier layer 5 is an oxide, and the heavy metal layer 6 can come into contact with this MgO. Since the heavy metal material is difficult to oxidize, the wettability and flatness of the interface may decrease, and there is a possibility that the perpendicular magnetic anisotropy and thus the tunnel resistance change rate (TMR ratio) may decrease.

[0040] In this regard, in the magnetic memory element 1 according to the embodiment, the barrier layer 5 contains not only MgO but also a predetermined material (such as Fe). This predetermined material diffuses and discharges to the interface between the free layer 4 and the barrier layer 5, thereby improving the wettability and flatness of the interface. It is possible to suppress the decrease in perpendicular magnetic anisotropy and thus suppress the decrease in the TMR ratio. Therefore, it is possible to achieve both the improvement of the VCMA efficiency and the suppression of the decrease in the TMR ratio. This will be described also referring to FIGS. 4 and 5.

[0041] FIG. 4 is a diagram showing an example of the improvement of the VCMA efficiency. The measured values in a configuration (Orthogonal MTJ) where the magnetization direction of the fixed layer 3 is in the in-plane direction and the magnetization direction of the free layer 4 is in the perpendicular direction are shown.

[0042] The horizontal axis of the graphs in FIGS. 4(A) and 4(B) indicates the magnetic flux density (T). The vertical axis of the graph indicates the magnitude of the magnetization of the free layer normalized by the saturation magnetization. The plurality of graph lines indicate the difference in the voltage (electric field), that is, the bias voltage applied to the magnetic memory element 1. In FIG. 4(A), the characteristics of a comparative example where the barrier layer 5 is a MgO layer are shown. In FIG. 4(B), the characteristics of the embodiment where the barrier layer 5 is a FeMgO layer are shown. The heavy metal layer 6 on the barrier layer 5 is an Ir layer with a thickness of 0.15 nm, and the free layer 4 thereon is a CoFe layer with a thickness of 0.8 nm. The heat treatment temperature after film formation is 400°C.

[0043] The horizontal axis of the graph in FIG. 4(C) indicates the bias voltage (mV). The vertical axis of the graph indicates the value obtained by multiplying the magnetic anisotropy constant by the thickness of the free layer 4 (μJ / m ,

[0044] ). The graph line A shows the comparative example, and the graph line B shows the embodiment.

[0044] The slope of the graph line indicates the VCMA efficiency. From graph line A, the VCMA efficiency of the magnetic memory element according to the comparative example can be determined, and its value is -85 (fJ / Vm). From graph line B, the VCMA efficiency of the magnetic memory element 1 according to the embodiment can be determined, and its value is -111 (fJ / Vm). It can be seen that the VCMA efficiency of the embodiment is improved compared to the VCMA efficiency of the comparative example.

[0045] Figure 5 shows an example of suppressing the decrease in the TMR ratio. A magnetic memory element according to a comparative example is referred to as magnetic memory element 1E and is shown in the figure. Figure 5(A) shows a cross-section of a part of magnetic memory element 1E. The barrier layer 5E of magnetic memory element 1E is an MgO layer. Figure 5(B) shows a cross-section of a part of magnetic memory element 1 according to the embodiment. The barrier layer 5 of magnetic memory element 1 is an FeMgO layer. Note that the reference numerals for the heavy metal layer 6 are omitted from the illustration.

[0046] As shown in Figure 5(A), in magnetic memory element 1E, the wettability of the free layer 4 is poor (the unevenness is large), and the flatness is reduced. As shown in Figure 5(B), in magnetic memory element 1, the wettability of the free layer 4 is improved, and the flatness is improved. In other words, the decrease in the TMR ratio is suppressed. The reason for the improved wettability is thought to be the concentration (deposition) of Fe at the interface.

[0047] Figure 6 shows an example of the composition of the barrier layer 5. Here, the content is expressed using composition ratios. Within a range that is not inconsistent, the content and composition ratios may be interpreted as appropriate.

[0048] Figure 6(A) shows the configuration of the magnetic memory element 1. In the bottom-pin type configuration, the fixed layer 3, barrier layer 5, heavy metal layer 6, and free layer 4 are stacked in this order in the positive Z-axis direction. The fixed layer 3 is a CoFeB layer, the free layer 4 is a CoFe layer, and the heavy metal layer 6 is an Ir layer. The barrier layer 5 includes barrier layer 52 (MgO layer) and barrier layer 51 (FeMgO layer) stacked in the positive Z-axis direction, similar to Figure 2(A) described earlier. The thickness of the barrier layer 5 (length in the Z-axis direction) is referred to as thickness t5 and is shown in the figure.

[0049] Figure 6(B) shows the area resistance RA (Ωμm) during magnetization reversal when the composition ratio (%) of Fe in the barrier layer 5 is changed. ２ The composition ratio and TMR ratio (%) are shown. Figure 6(C) shows a plot graph of the TMR ratio (%). The TMR ratio has a maximum value or is close to it when the composition ratio of Fe is in the range of approximately 5 at% to 10 at%. That is, an example of the lower limit of the composition ratio of Fe is 5 at%. An example of the upper limit of the composition ratio of Fe is 10 at%. For example, the composition ratio of Fe in the barrier layer 5 may be 5 at% or more and 10 at% or less.

[0050] Figure 6(D) shows the area resistance RA (Ωμm) when the thickness t5 (nm) of the barrier layer 5 is changed while the Fe composition ratio is fixed at 10%. ２ The impedance and TMR ratio (%) are shown. 40 Ωμm ２ It is desirable to obtain an area resistance value RA of a certain degree. For example, the area resistance value RA of the magnetic memory element 1 is 40 Ω μm. ２ The above is acceptable. An example of a lower limit for the thickness t5 of the barrier layer 5 is 1.3 nm. For example, the thickness t5 of the barrier layer 5 may be 1.3 nm or more.

[0051] 2. Examples and Modifications Several examples and modifications based on the technologies of the embodiments described above will be described.

[0052] <Bottom-pin type, free layer = CoFe layer> Figure 7 shows an example. A comparative example is also shown. In the bottom-pin type configuration, the fixed layer, barrier layer, heavy metal layer and free layer are stacked in this order in the positive Z-axis direction. The fixed layer 3 is a CoFeB layer, the free layer 4 is a CoFe layer, and the heavy metal layer 6 is an Ir layer. The barrier layer 5E of the magnetic memory element 1E in the comparative example is an MgO layer.

[0053] The barrier layer 5 of the magnetic memory element 1 according to Example 1 has the same configuration as shown in Figure 2(A) described earlier, and includes a barrier layer 52 (MgO layer) and a barrier layer 51 (FeMgO layer) stacked sequentially in the positive Z-axis direction. The barrier layer 5 of the magnetic memory element 1 according to Example 2 has the same configuration as shown in Figure 2(B) described earlier, and includes a barrier layer 51 and a barrier layer 52 stacked sequentially in the positive Z-axis direction.

[0054] The barrier layer 5 of the magnetic memory element 1 according to Example 3 has the same configuration as shown in Figure 2(C) described earlier, and includes barrier layer 51-1, barrier layer 52, and barrier layer 51-2 stacked in order in the positive Z-axis direction. The barrier layer 5 of the magnetic memory element 1 according to Example 4 has the same configuration as shown in Figure 2(D) described earlier, and includes barrier layer 52-1, barrier layer 51, and barrier layer 52-2 stacked in order in the positive Z-axis direction. The barrier layer 5 of the magnetic memory element 1 according to Example 5 has the same configuration as shown in Figure 2(E) described earlier, and includes barrier layer 51.

[0055] The magnetic memory element 1 according to Examples 1 to 5 described above differs from the magnetic memory element 1E according to the comparative example in that the barrier layer 5 includes not only MgO but also Fe (an example of a predetermined material). This makes it possible to achieve both improved VCMA efficiency and suppression of a decrease in the TMR ratio.

[0056] <Top-pin type, free layer = CoFe layer> Figure 8 shows an example. A comparative example is also shown. In the top-pin type configuration, the free layer, heavy metal layer, barrier layer and fixed layer are stacked in this order in the positive Z-axis direction. The fixed layer 3 is a CoFeB layer, the free layer 4 is a CoFe layer, and the heavy metal layer 6 is an Ir layer. The barrier layer 5E of the magnetic memory element 1E in the comparative example is an MgO layer.

[0057] The barrier layer 5 of the magnetic memory element 1 according to Example 11 includes a barrier layer 51 and a barrier layer 52 stacked sequentially in the negative Z-axis direction. The barrier layer 5 of the magnetic memory element 1 according to Example 12 includes a barrier layer 52 and a barrier layer 51 stacked sequentially in the negative Z-axis direction.

[0058] The barrier layer 5 of the magnetic memory element 1 according to Example 13 includes barrier layer 51-1, barrier layer 52, and barrier layer 51-2 stacked in order in the negative Z-axis direction. The barrier layer 5 of the magnetic memory element 1 according to Example 14 includes barrier layer 52-1, barrier layer 51, and barrier layer 52-2 stacked in order in the negative Z-axis direction. The barrier layer 5 of the magnetic memory element 1 according to Example 15 includes barrier layer 51.

[0059] The magnetic memory elements 1 according to Examples 11 to 15 described above differ from the magnetic memory element 1E according to the comparative example in that the barrier layer 5 includes not only MgO but also Fe (an example of a predetermined material). Even in a top-pin type configuration, it is possible to achieve both improved VCMA efficiency and suppression of a decrease in the TMR ratio.

[0060] <Bottom-pin type, free layer = CoFeB layer> Figure 9 shows an example. Comparative examples are also shown. The comparative examples and examples 21 to 25 shown in Figure 9 differ from the comparative examples and examples 1 to 5 in Figure 7 described earlier in that the free layer 4 contains CoFeB. Even with this bottom-pin type configuration, it is possible to achieve both improved VCMA efficiency and suppression of the decrease in TMR ratio.

[0061] <Top-pin type, free layer = CoFeB layer> Figure 10 shows an example. Comparative examples are also shown. The comparative examples and examples 31 to 35 shown in Figure 10 differ from the comparative examples and examples 11 to 15 in Figure 8 described earlier in that the free layer 4 contains CoFeB. Even with this top-pin type configuration, it is possible to achieve both improved VCMA efficiency and suppression of the decrease in TMR ratio.

[0062] <Cap Barrier Layer> In one embodiment, the magnetic memory element 1 may further include a cap barrier layer. This will be explained with reference to Figure 11.

[0063] Figure 11 shows an example of the schematic configuration of a magnetic memory element 1. The magnetic memory element 1 shown in Figure 11 differs from the configuration shown in Figure 3 described earlier in that it further includes a cap barrier layer 7 and two heavy metal layers 6.

[0064] The cap barrier layer 7 is provided on the opposite side of the free layer 4 from the barrier layer 5. The cap barrier layer 7 may contain MgO. The cap barrier layer 7 may further contain a predetermined material (at least one of Fe, Mn, V, Ti, and Co), similar to the barrier layer 5.

[0065] The first of the two heavy metal layers is referred to as heavy metal layer 6-1 and is shown in the figure. The second heavy metal layer is referred to as heavy metal layer 6-2 and is shown in the figure. Heavy metal layer 6-1 and heavy metal layer 6-2 are located on opposite sides of the free layer 4.

[0066] The magnetic memory element 1 shown in Figure 11 is of the bottom pin type and includes a fixed layer 3, a barrier layer 5, a heavy metal layer 6-1, a free layer 4, a heavy metal layer 6-2, and a cap barrier layer 7, which are stacked in order in the positive Z-axis direction.

[0067] The heavy metal layer 6-1 is located between the free layer 4 and the barrier layer 5, and is therefore inserted at the interface between the free layer 4 and the barrier layer 5 (between surfaces 4b and 5a). The surface of the free layer 4 on the positive Z-axis side is referred to as surface 4a and is shown in the figure. The surface of the cap barrier layer 7 on the negative Z-axis side is referred to as surface 7b and is shown in the figure. Surface 4a of the free layer 4 and surface 7b of the cap barrier layer 7 may correspond to the interface between the free layer 4 and the cap barrier layer 7. The heavy metal layer 6-2 is located between the free layer 4 and the cap barrier layer 7, and is therefore inserted at the interface between the free layer 4 and the cap barrier layer 7 (between surfaces 4a and 7b).

[0068] The thickness (length in the Z-axis direction) of the heavy metal layer 6 in the magnetic memory element 1 is referred to as thickness t6. More specifically, the thickness of heavy metal layer 6-1 is referred to as thickness t61 and is shown in the figure. The thickness of heavy metal layer 6-2 is referred to as thickness t62 and is shown in the figure. The thickness t6 of the heavy metal layer 6 corresponds to the sum of the thickness t61 of heavy metal layer 6-1 and the thickness t62 of heavy metal layer 6-2 (t6 = t61 + t62). The design of the heavy metal layer 6 will be explained with reference to Figures 12 and 13.

[0069] Figures 12 and 13 show examples of the design of the heavy metal layer 6. The heat treatment temperature after film formation is 350°C.

[0070] Figure 12(A) shows the magnetic anisotropy constant Ku when the thickness t61 of the heavy metal layer 6-1 is varied, with the heavy metal layer 6-2 absent (thickness t62 = 0 nm). The horizontal axis of the graph represents the thickness t61 (nm) of the heavy metal layer 6-1. The vertical axis of the graph represents the value Ku・t (μJ / m²), which is the magnetic anisotropy constant Ku multiplied by the thickness t of the free layer 4. ２ ) indicates.

[0071] Figure 12(B) shows the magnetic anisotropy constant Ku when the heavy metal layer 6-1 is absent (thickness t61 = 0 nm) and the thickness t62 of the heavy metal layer 6-2 is varied. The horizontal axis of the graph represents the thickness t62 (nm) of the heavy metal layer 6-2. The vertical axis of the graph represents the value Ku・t (μJ / m²), which is the magnetic anisotropy constant Ku multiplied by the thickness t of the free layer 4. ２ ) indicates.

[0072] The magnetic anisotropy constant Ku increases (reaches a peak) when the thickness t61 of the heavy metal layer 6-1 or the thickness t62 of the heavy metal layer 6-2 is around 0.15 nm. From the viewpoint of improving the magnetic anisotropy constant Ku, the range including that thickness value may be selected as the range of the thickness t61 of the heavy metal layer 6-1 or the thickness t62 of the heavy metal layer 6-2, i.e., the thickness t6 of the heavy metal layer 6. For example, the thickness t6 of the heavy metal layer 6 may be 0.05 nm or more and 0.25 nm or less.

[0073] Figure 13 shows various characteristics when the thickness t6 (= t61 + t62) of the heavy metal layer 6 is fixed at 0.15 nm while the thickness t61 of the heavy metal layer 6-1 is varied. The horizontal axis of the graph shows the thickness t61 (nm) of the heavy metal layer 6-1. The vertical axis of the graph in Figure 13 (A) shows the TMR ratio (%). The vertical axis of the graph in Figure 13 (B) shows the value Ku・t (μJ / m²), which is obtained by multiplying the magnetic anisotropy constant Ku by the thickness t of the free layer 4. ２ This shows the VCCA efficiency (fJ / Vm). The vertical axis of the graph in Figure 13(C) shows the VCCA efficiency (fJ / Vm).

[0074] By reducing the thickness t61 of the heavy metal layer 6-1, a high TMR ratio can be obtained while maintaining VCMA efficiency. An example of an upper limit for the thickness t61 of the heavy metal layer 6-1 is 0.1 nm. For example, the thickness t61 of the heavy metal layer 6-1 may be 0.1 nm or less. An example of a lower limit for the thickness t61 of the heavy metal layer 6-1 is 0.05 nm. For example, the thickness t61 of the heavy metal layer 6-1 may be between 0.05 nm and 0.1 nm.

[0075] Several embodiments and modifications of the magnetic memory element 1, including the cap barrier layer 7 described above, will be described.

[0076] <Bottom-pin type, free layer = CoFe layer> Figures 14 to 18 show examples and modified examples. Comparative examples are also shown. In the bottom-pin type configuration, the fixed layer 3 is a CoFeB layer, the free layer 4 is a CoFe layer, and the heavy metal layer 6 is an Ir layer. In the magnetic memory element 1E according to Comparative Example 1b shown in Figure 14, the barrier layer 5E and the cap barrier layer 7E are both MgO layers.

[0077] The barrier layer 5 and cap barrier layer 7 of the magnetic memory element 1 according to Example 1a, Modification 1-1, and Modification 1-2 shown in Figure 14 include Fe as well as MgO. In this example, the barrier layer 5 has the same configuration as in Figure 2(A) described earlier and includes a barrier layer 52 (MgO layer) and a barrier layer 51 (FeMgO layer) stacked sequentially in the positive Z-axis direction. The cap barrier layer 7 is a FeMgO layer.

[0078] The heavy metal layer 6 of the magnetic memory element 1 according to Example 1a includes heavy metal layer 6-1. The heavy metal layer 6 of the magnetic memory element 1 according to Modification 1-1 includes heavy metal layer 6-2. The heavy metal layer 6 of the magnetic memory element 1 according to Modification 1-2 includes heavy metal layer 6-1 and heavy metal layer 6-2.

[0079] The magnetic memory element 1 according to Example 1a, Modification 1-1, and Modification 1-2 described above differs from the magnetic memory element 1E according to Comparative Example 1b, in particular, in that the barrier layer 5 and cap barrier layer 7 include not only MgO but also Fe (an example of a predetermined material). Fe is diffused and discharged at the interface between these layers and the free layer 4 (magnetic layer), thereby improving the wettability and flatness of the interface. This makes it possible to achieve both improved VCMA efficiency and suppression of a decrease in the TMR ratio.

[0080] In the magnetic memory element 1 according to Example 2a, Modification 2-1, and Modification 2-2 shown in Figure 15, the barrier layer 5 and cap barrier layer 7 also contain Fe as well as MgO. In this example, the barrier layer 5 has the same configuration as in Figure 2(B) described earlier and includes barrier layer 51 and barrier layer 52 stacked sequentially in the positive Z-axis direction. The heavy metal layer 6 of the magnetic memory element 1 according to Example 2a includes heavy metal layer 6-1. The heavy metal layer 6 of the magnetic memory element 1 according to Modification 2-1 includes heavy metal layer 6-2. The heavy metal layer 6 of the magnetic memory element 1 according to Modification 2-2 includes heavy metal layer 6-1 and heavy metal layer 6-2. This makes it possible to achieve both improved VCMA efficiency and suppression of a decrease in the TMR ratio.

[0081] In the magnetic memory element 1 according to Example 3a, Modification 3-1, and Modification 3-2 shown in Figure 16, the barrier layer 5 and the cap barrier layer 7 also contain Fe as well as MgO. In this example, the barrier layer 5 has the same configuration as in Figure 2(C) described earlier and includes barrier layer 51-1, barrier layer 52, and barrier layer 51-2 stacked sequentially in the positive Z-axis direction. The heavy metal layer 6 of the magnetic memory element 1 according to Example 3a includes heavy metal layer 6-1. The heavy metal layer 6 of the magnetic memory element 1 according to Modification 3-1 includes heavy metal layer 6-2. The heavy metal layer 6 of the magnetic memory element 1 according to Modification 3-2 includes heavy metal layer 6-1 and heavy metal layer 6-2. This makes it possible to achieve both improved VCMA efficiency and suppression of a decrease in the TMR ratio.

[0082] In the magnetic memory element 1 according to Example 4a, Modification 4-1, and Modification 4-2 shown in Figure 17, the barrier layer 5 and the cap barrier layer 7 also contain Fe as well as MgO. In this example, the barrier layer 5 has the same configuration as Figure 2(D) described earlier and includes barrier layer 52-1, barrier layer 51, and barrier layer 52-2 stacked sequentially in the positive Z-axis direction. The heavy metal layer 6 of the magnetic memory element 1 according to Example 4a includes heavy metal layer 6-1. The heavy metal layer 6 of the magnetic memory element 1 according to Modification 4-1 includes heavy metal layer 6-2. The heavy metal layer 6 of the magnetic memory element 1 according to Modification 4-2 includes heavy metal layer 6-1 and heavy metal layer 6-2. It is possible to achieve both improved VCMA efficiency and suppression of a decrease in the TMR ratio.

[0083] In the magnetic memory element 1 according to Example 5a, Modification 5-1, and Modification 5-2 shown in Figure 18, the barrier layer 5 and the cap barrier layer 7 also contain Fe as well as MgO. In this example, the barrier layer 5 has the same configuration as in Figure 2(E) described earlier and includes a barrier layer 51. The heavy metal layer 6 of the magnetic memory element 1 according to Example 5a includes heavy metal layer 6-1. The heavy metal layer 6 of the magnetic memory element 1 according to Modification 5-1 includes heavy metal layer 6-2. The heavy metal layer 6 of the magnetic memory element 1 according to Modification 5-2 includes heavy metal layer 6-1 and heavy metal layer 6-2. It is possible to achieve both improved VCMA efficiency and suppression of a decrease in the TMR ratio.

[0084] <Bottom pin type, cap barrier layer = MgO layer> Figure 19 shows examples and modified examples. Examples 1b, modified examples 1-3 and 1-4 shown in Figure 19 differ from examples 1a, modified examples 1-1 and 1-2 shown in Figure 14 described earlier in that the cap barrier layer 7 is an MgO layer. Even in this case, since the barrier layer 5 contains Fe, it is possible to achieve both improved VCMA efficiency and suppression of a decrease in the TMR ratio.

[0085] In addition, in the embodiments and modified examples shown in Figures 15 to 18 described above, the cap barrier layer 7 may be replaced with an MgO layer.

[0086] <Bottom pin type, free layer = CoFeB layer> Figure 20 shows examples and modified examples. Examples 21a, modified example 21-1, and modified example 21-2 shown in Figure 20 differ from examples 1a, modified example 1-1, and modified example 1-2 in Figure 14 described earlier in that the free layer 4 is a CoFeB layer. Even with this configuration, it is possible to achieve both improved VCMA efficiency and suppression of a decrease in the TMR ratio.

[0087] In addition, in the embodiments and modified examples shown in Figures 15 to 18 described above, the free layer 4 may be replaced with a CoFeB layer.

[0088] <Bottom pin type, free layer = CoFeB layer, cap barrier layer = MgO layer> Figure 21 shows examples and modified examples. Examples 21b, modified example 21-3, and modified example 21-4 shown in Figure 21 differ from examples 1a, modified example 1-1, and modified example 1-2 of Figure 14 described earlier in that the free layer 4 and the cap barrier layer 7 are a CoFeB layer and an MgO layer, respectively. Even with this configuration, it is possible to achieve both improved VCMA efficiency and suppression of a decrease in the TMR ratio.

[0089] In addition, in the embodiments and modified examples shown in Figures 15 to 18 described above, the free layer 4 and the cap barrier layer 7 may be replaced with a CoFeB layer and an MgO layer.

[0090] <Top-pin type> Figures 22 to 25 show examples and modified examples. In the top-pin type configuration, the fixed layer 3 is a CoFeB layer, and the heavy metal layer 6 is an Ir layer. The barrier layer 5 includes barrier layer 52 and barrier layer 51 which are stacked sequentially in the negative Z-axis direction. For example, in these various top-pin type configurations shown in Figures 22 to 25, it is possible to achieve both improved VCMA efficiency and suppression of a decrease in the TMR ratio.

[0091] <Top-pin type, free layer = CoFe layer> The free layer 4 of the magnetic memory element 1 according to Example 12, Modification 12-1 and Modification 12-2 shown in Figure 22 is a CoFe layer. The heavy metal layer 6 of the magnetic memory element 1 according to Example 12 includes heavy metal layer 6-1. The heavy metal layer 6 of the magnetic memory element 1 according to Modification 12-1 includes heavy metal layer 6-2. The heavy metal layer 6 of the magnetic memory element 1 according to Modification 12-2 includes heavy metal layer 6-1 and heavy metal layer 6-2.

[0092] Note that the configuration of the barrier layer 5 is not limited to the example shown in Figure 22. Any configuration similar to those described earlier in Figures 2(A) to (E) may be adopted. The same applies to Figures 23 to 25.

[0093] <Top-pin type, free layer = CoFe layer, cap barrier layer = MgO layer> Example 12b, modified example 12-3 and modified example 12-4 shown in Figure 23 differ from Example 12, modified example 12-1 and modified example 12-2 shown in Figure 22, which were described earlier, in that the cap barrier layer 7 is an MgO layer.

[0094] <Top-pin type, free layer = CoFeB layer> The magnetic memory element 1 according to Example 32a, Modification 32-1 and Modification 32-2 shown in Figure 24 differs from Example 12, Modification 12-1 and Modification 12-2 shown in Figure 22, which were described earlier, in that the free layer 4 is a CoFeB layer.

[0095] <Top-pin type, free layer = CoFeB layer, cap barrier layer = MgO layer> The magnetic memory element 1 according to Example 32b, Modification 32-3 and Modification 32-4 shown in Figure 25 differs from Example 12, Modification 12-1 and Modification 12-2 shown in Figure 22, which were described earlier, in that the free layer 4 and the cap barrier layer 7 are a CoFeB layer and an MgO layer, respectively.

[0096] <Lamination of Free Layers> In one embodiment, the free layer 4 may have a laminated structure. This will be explained with reference to Figures 26 and 27.

[0097] Figure 26 shows an example of the schematic configuration of the free layer 4. The free layer 4 includes multiple layers, in this example, two types of layers. The first layer is referred to as free layer 41 and is shown in the figure. The second layer is referred to as free layer 42 and is shown in the figure. Free layer 41 is a CoFe layer. Free layer 42 is an Fe layer. In this example, free layer 41 and free layer 42 are stacked in this order in the positive Z-axis direction.

[0098] The thickness of free layer 4 (length in the Z-axis direction) is referred to as thickness t4 and is shown in the figure. The thickness of free layer 41 is referred to as thickness t41 and is shown in the figure. The thickness of free layer 42 is referred to as thickness t42 and is shown in the figure. The thickness t4 of free layer 4 corresponds to the sum of the thickness t41 of free layer 41 and the thickness t42 of free layer 42 (t4 = t41 + t42).

[0099] Figure 27 is a diagram showing an example of the design of the free layer 4. The heat treatment temperature after film formation is 400°C. The heavy metal layer 6-1 is an Ir layer with a thickness of 0.05 nm, and the heavy metal layer 6-2 is an Ir layer with a thickness of 0.1 nm. The horizontal axis of the graph indicates the thickness t4 (nm) of the free layer 4.

[0100] The vertical axis of the graph in (A) of Figure 27 indicates the value Ku·t (μJ / m ２ ) obtained by multiplying the magnetic anisotropy constant Ku by the thickness of the free layer 4. The characteristics when the thickness t41 of the free layer 41 is changed between 0.6 nm and 1.0 nm and when the thickness t42 of the free layer 42 is 0 nm (i.e., when there is no free layer 42) are shown. The vertical axis of the graph in (B) of Figure 27 indicates the VCMA efficiency (fJ / Vm). The characteristics when the thickness t41 of the free layer 41 is changed between 0.6 nm and 0.8 nm and when the thickness t42 of the free layer 42 is 0 nm are shown. The various values shown in (A) and (B) of Figure 27 are measurement values in a configuration (Orthogonal MTJ) where the magnetization direction of the fixed layer 3 is in the in-plane direction and the magnetization direction of the free layer 4 is in the perpendicular direction.

[0101] The vertical axis of the graph in (C) of Figure 27 indicates the value obtained by dividing the product of the coercive force H ｃ and the magnetic permeability μ ０ by the voltage (mT / V), that is, the change in coercive force with respect to voltage. This value is a measurement value in a configuration (Perpendicular MTJ) where the magnetization directions of both the fixed layer 3 and the free layer 4 are in the perpendicular direction.

[0102] By having the free layer 4 have a stacked structure including the free layer 41 and the free layer 42, the VCMA efficiency is further improved. The VCMA efficiency becomes the largest when the total thickness of the thickness t41 of the free layer 41 and the thickness t42 of the free layer 42, that is, the thickness t4 (= t41 + t42) of the free layer 4, is 1.0 nm or more and 1.1 nm or less.

[0103] From the perspective of improving VCMA efficiency, regarding the optimal thickness combination, an example of the lower limit of the thickness t41 of the free layer 41 is 0.6 nm. An example of the upper limit of the thickness t41 of the free layer 41 is 0.9 nm. For example, the thickness t41 of the free layer 41 may be between 0.6 nm and 0.9 nm. An example of the lower limit of the thickness t42 of the free layer 42 is 0 nm. A free layer thickness t42 of 0 nm means a configuration without a free layer 42. An example of the upper limit of the thickness t42 of the free layer 42 is 0.7 nm. For example, the thickness t42 of the free layer 42 may be between 0 nm and 0.7 nm.

[0104] Several embodiments and modifications of a magnetic memory element 1 including a free layer 4 having a stacked structure are described below.

[0105] <Bottom pin type, free layer = CoFe layer / Fe layer> Figure 28 shows examples and modified examples. Examples 51a, modified example 51-1, modified example 51-2 and Example 51b shown in Figure 28 differ from Examples 1a, modified example 1-1 and modified example 1-2 of Figure 14 described earlier in that the free layer 4 includes free layer 41 and free layer 42. Example 51b differs from Example 51a in that the cap barrier layer 7 is an MgO layer. The VCMA efficiency can be further improved by having a laminated structure for the free layer 4.

[0106] Figure 29 shows an example. The cap barrier layer 7 is not shown, but the cap barrier layer 7 may be either a FeMgO layer or an MgO layer.

[0107] The barrier layer 5 of the magnetic memory element 1 according to Example 52 has the same configuration as shown in Figure 2(B) described earlier, and includes barrier layer 51 and barrier layer 52 stacked sequentially in the positive Z-axis direction. The magnetic memory element 1 according to Example 53 has the same configuration as shown in Figure 2(C) described earlier, and includes barrier layer 51-1, barrier layer 52 and barrier layer 51-2 stacked sequentially in the positive Z-axis direction.

[0108] The magnetic memory element 1 according to Example 54 has the same configuration as shown in Figure 2(D) described earlier, and includes barrier layers 52-1, 51, and 52-2 stacked sequentially in the positive Z-axis direction. The magnetic memory element 1 according to Example 55 has the same configuration as shown in Figure 2(E) described earlier, and includes barrier layer 51.

[0109] For example, the VCMA efficiency can be further improved in the various configurations described above. Figure 29 illustrates a configuration in which the heavy metal layer 6 includes heavy metal layer 6-1, but the heavy metal layer 6 may also include heavy metal layer 6-2 in place of or together with heavy metal layer 6-1.

[0110] <Top-pin type, free layer = Fe layer / CoFe layer> Figure 30 shows examples and modified examples. In the top-pin type configuration, the fixed layer 3 is a CoFeB layer, the heavy metal layer 6 is an Ir layer, and the cap barrier layer 7 is a FeMgO layer.

[0111] The free layer 4 of the magnetic memory element 1 according to Embodiment 61, Modification 61-1, and Modification 61-2 shown in Figure 30 includes free layer 41 and free layer 42 stacked sequentially in the negative Z-axis direction. The barrier layer 5 includes barrier layer 51 and barrier layer 52 stacked sequentially in the negative Z-axis direction.

[0112] The magnetic memory element 1 according to Example 61 includes a heavy metal layer 6-1 inserted between the free layer 41 and the barrier layer 52. The magnetic memory element 1 according to Modification 61-1 includes a heavy metal layer 6-2 inserted between the free layer 42 and the cap barrier layer 7. The magnetic memory element 1 according to Modification 61-2 includes heavy metal layers 6-1 and 6-2. For example, even in such a top-pin type configuration, the VCMA efficiency can be further improved by stacking the free layers 4.

[0113] Figure 31 shows an example. The cap barrier layer 7 is not shown, but the cap barrier layer 7 may be either a FeMgO layer or an MgO layer.

[0114] The barrier layer 5 of the magnetic memory element 1 according to Example 62 includes barrier layer 52 and barrier layer 51 stacked sequentially in the negative Z-axis direction. The barrier layer 5 of the magnetic memory element 1 according to Example 63 includes barrier layer 51-1, barrier layer 52 and barrier layer 51-2 stacked sequentially in the negative Z-axis direction.

[0115] The barrier layer 5 of the magnetic memory element 1 according to Example 64 includes barrier layer 52-1, barrier layer 51, and barrier layer 52-2 stacked sequentially in the negative Z-axis direction. The barrier layer 5 of the magnetic memory element 1 according to Example 65 includes barrier layer 51.

[0116] For example, the VCMA efficiency can be further improved in the various configurations described above. Although Figures 30 and 31 illustrate a configuration in which the heavy metal layer 6 includes heavy metal layer 6-1, the heavy metal layer 6 may also include heavy metal layer 6-2 in place of or together with heavy metal layer 6-1.

[0117] 3. Summary The technologies described above can be identified, for example, as follows: One of the disclosed technologies is a magnetic memory element 1. As described with reference to Figures 1 to 31, the magnetic memory element 1 comprises a fixed layer 3 with a fixed magnetization direction, a free layer 4 whose magnetization direction can be reversed, and a barrier layer 5 provided between the fixed layer 3 and the free layer 4 so as to obtain a TMR effect, and is a magnetic memory element 1 that reverses the magnetization of the free layer 4 by a voltage-induced magnetic anisotropy control (VCMA) effect, wherein the barrier layer 5 includes MgO and at least one of Fe, Co, Mn, V, and Ti (a predetermined material). As an example, the predetermined material may be Fe.

[0118] According to the magnetic memory element 1 described above, the barrier layer 5 contains not only MgO but also a predetermined material. This makes it possible to improve the flatness and crystal orientation of the interface between the barrier layer 5 and the magnetic layer in contact with it, specifically the free layer 4, compared to the case where the barrier layer 5 contains only MgO (and does not contain the predetermined material). Therefore, the VCMA efficiency can be improved.

[0119] As explained with reference to Figures 1 and 6, the magnetic memory element 1 has an area resistance of 40 Ωμm ２The device may satisfy at least one of the following conditions: the device meets the above requirements, and the barrier layer 5 has a thickness of 1.3 nm or more and 3.0 nm or less. This increases the effect of voltage application and makes it possible to realize a device suitable for reversing the magnetization of the free layer 4 by the VCMA effect. Furthermore, the content of the predetermined material (Fe, etc.) in the barrier layer 5 may be 5 at% or more and 10 at% or less. For example, such a configuration can obtain a large TMR effect.

[0120] As explained with reference to Figures 2, 6-10, 14-25, 28-31, etc., the barrier layer 5 may have a laminated structure and include a barrier layer 51 (first barrier layer) containing MgO and a predetermined material, and a barrier layer 52 (second barrier layer) containing MgO. Alternatively, the barrier layer 5 may have a single-layer structure. Regardless of whether the barrier layer 5 has a laminated structure or a single-layer structure, the VCMA efficiency can be improved.

[0121] As explained with reference to Figures 1, 5-10, 14-26, and 28-31, the free layer 4 may contain CoFe and may further contain B. For example, a layer containing such a magnetic material (magnetic layer) can be used as the free layer 4. As explained with reference to Figures 1 and 26-31, the free layer 4 has a laminated structure and may include a free layer 41 containing CoFe (first free layer) and a free layer 42 containing Fe (second free layer). Alternatively, the free layer 4 may have a single-layer structure (only a CoFe layer). In particular, using a free layer 4 with a laminated structure increases the possibility of further improving the VCMA efficiency. For example, the thickness t4 of the free layer 4 may be 0.6 nm or more and 1.5 nm or less.

[0122] As explained with reference to Figures 3, 7 to 25, and 28 to 31, the magnetic memory element 1 further comprises a heavy metal layer 6 provided on the free layer 4, and the heavy metal layer 6 may contain at least one of Ir and Os. For example, the heavy metal layer 6 may be an Ir layer. By providing such a heavy metal layer 6, the VCMA efficiency can be further improved. In addition, the decrease in wettability and flatness of the interface, i.e., the decrease in the TMR ratio, which may occur due to the heavy metal material's resistance to oxidation, is suppressed by the diffusion and discharge of a predetermined material contained in the barrier layer 5 to the interface between the free layer 4 and the barrier layer 5. Therefore, it is possible to achieve both improved VCMA efficiency and suppression of the decrease in the TMR ratio.

[0123] As explained with reference to Figures 3 and 11-13, the thickness of the heavy metal layer 6 may be 0.05 nm or more and 0.25 nm or less. For example, by providing a heavy metal layer 6 of such thickness, a large magnetic anisotropy constant Ku can be obtained. As explained with reference to Figures 11, 14-25 and 28-31, the heavy metal layer 6 includes a heavy metal layer 6-1 (first heavy metal layer) located between the free layer 4 and the barrier layer 5, and a heavy metal layer 6-2 (second heavy metal layer) located on the opposite side of the barrier layer 5 across the free layer 4, and the thickness of the heavy metal layer 6-1 may be 0.05 nm or more and 0.1 nm or less. A high TMR ratio can be obtained while maintaining VCMA efficiency.

[0124] The magnetic memory element 1 may be of the bottom-pin type. For example, as explained with reference to Figure 1(A), Figure 3, Figure 6, Figure 7, Figure 9, Figure 11, Figures 14 to 21, Figure 28 and 29, the magnetic memory element 1 may further include a substrate 2, and the fixed layer 3 may be located between the substrate 2 and the free layer 4. Alternatively, the magnetic memory element 1 may be of the top-pin type. For example, as explained with reference to Figure 1(B), Figure 8, Figure 10, Figures 22 to 25, Figure 30 and 31, the magnetic memory element 1 may further include a substrate 2, and the free layer 4 may be located between the substrate 2 and the fixed layer 3.

[0125] As explained with reference to Figures 11, 14 to 25, and 28 to 31, the magnetic memory element 1 further comprises a cap barrier layer 7 located on the opposite side of the barrier layer 5 from the free layer 4, and the cap barrier layer 7 may contain MgO. The cap barrier layer 7 may also contain MgO and the predetermined material described above. Even with such a configuration including the cap barrier layer 7, the VCMA efficiency can be improved. In particular, when the cap barrier layer 7 contains not only MgO but also the predetermined material, the flatness and crystal orientation of the interface with the magnetic layer in contact with the cap barrier layer 7, specifically the free layer 4, can be improved, and a decrease in the TMR ratio can be suppressed.

[0126] The effects described in this disclosure are merely illustrative and not limited to those disclosed. Other effects may also occur.

[0127] While embodiments of this disclosure have been described above, the technical scope of this disclosure is not limited to the embodiments described above, and various modifications are possible without departing from the spirit of this disclosure. Furthermore, components from different embodiments and modifications may be combined as appropriate.

[0128] Furthermore, this technology can also take the following configurations: (1) A magnetic memory element that reverses the magnetization of the free layer by voltage magnetic anisotropy control (VCMA) effect by applying a voltage, comprising: a fixed layer with a fixed magnetization direction; a free layer whose magnetization direction can be reversed; and a barrier layer provided between the fixed layer and the free layer so as to obtain a tunnel magnetoresistance (TMR) effect, wherein the barrier layer contains MgO and at least one of Fe, Co, Mn, V, and Ti. (2) Area resistance value of 40 Ωμm ２(1) A magnetic memory element that satisfies at least one of the following conditions: (1) The barrier layer is 1.3 nm or more and (2) or (3) The barrier layer contains at least one of the Fe, Co, Mn, V and Ti in an amount of 5 at% or more and (2) or (3) (7) The magnetic memory element according to any one of (1) to (6), wherein the free layer comprises CoFe. (8) The magnetic memory element according to (7), wherein the free layer further comprises B. (9) The magnetic memory element according to any one of (1) to (8), wherein the free layer has a stacked structure and comprises a first free layer comprising CoFe and a second free layer comprising Fe. (10) The magnetic memory element according to any one of (1) to (8), wherein the free layer has a single-layer structure. (11) The magnetic memory element according to any one of (1) to (10), wherein the thickness of the free layer is 0.6 nm or more and 1.5 nm or less. (12) The magnetic memory element according to any one of (1) to (11), further comprising a heavy metal layer provided on the free layer, wherein the heavy metal layer comprises at least one of Ir and Os. (13) The magnetic memory element according to (12), wherein the heavy metal layer is an Ir layer. (14) The magnetic memory element according to (12) or (13), wherein the thickness of the heavy metal layer is 0.05 nm or more and 0.25 nm.(15) The magnetic memory element according to any one of (12) to (14), wherein the heavy metal layer comprises a first heavy metal layer located between the free layer and the barrier layer, and a second heavy metal layer located on the opposite side of the free layer from the barrier layer, and the thickness of the first heavy metal layer is 0.05 nm or more and 0.1 nm or less. (16) The magnetic memory element according to any one of (1) to (15), further comprising a substrate, wherein the fixed layer is located between the substrate and the free layer. (17) The magnetic memory element according to any one of (1) to (15), further comprising a substrate, wherein the free layer is located between the substrate and the fixed layer. (18) The magnetic memory element according to any one of (1) to (17), further comprising a cap barrier layer located on the opposite side of the free layer from the barrier layer, wherein the cap barrier layer contains MgO. (19) The magnetic memory element according to (18), wherein the cap barrier layer comprises MgO and at least one of Fe, Co, Mn, V, and Ti.

[0129] 1. Magnetic memory element 2. Substrate 3. Fixed layer 4. Free layer 41. Free layer 42. Free layer 5. Barrier layer 5a. Surface 51. Barrier layer 52. Barrier layer 6. Heavy metal layer 6-1. Heavy metal layer 6-2. Heavy metal layer 7. Cap barrier layer 7b. Surface t4. Thickness t41. Thickness t42. Thickness t5. Thickness t6. Thickness t61. Thickness t62. Thickness

Claims

1. A magnetic memory element comprising: a fixed layer with a fixed magnetization direction; a free layer whose magnetization direction can be reversed; and a barrier layer provided between the fixed layer and the free layer to obtain a tunnel magnetoresistance (TMR) effect, wherein the magnetization of the free layer is reversed by a voltage-induced magnetic anisotropy control (VCMA) effect, the barrier layer comprising MgO and at least one of Fe, Co, Mn, V, and Ti.

2. Area resistance value is 40 Ωμm ２ A magnetic memory element according to claim 1, satisfying at least one of the following conditions: the above, and the thickness of the barrier layer being 1.3 nm or more and 3.0 nm or less.

3. The magnetic memory element according to claim 1, wherein the content of at least one of Fe, Co, Mn, V, and Ti in the barrier layer is 5 at% or more and 10 at% or less.

4. The magnetic memory element according to claim 1, wherein the barrier layer has a laminated structure and comprises: a first barrier layer containing MgO and at least one of Fe, Co, Mn, V, and Ti; and a second barrier layer containing MgO.

5. The magnetic memory element according to claim 1, wherein the barrier layer has a single-layer structure.

6. The magnetic memory element according to claim 1, wherein at least one of Fe, Co, Mn, V, and Ti is Fe.

7. The magnetic memory element according to claim 1, wherein the free layer contains CoFe.

8. The magnetic memory element according to claim 7, wherein the free layer further comprises B.

9. The magnetic memory element according to claim 1, wherein the free layer has a stacked structure and comprises a first free layer containing CoFe and a second free layer containing Fe.

10. The magnetic memory element according to claim 1, wherein the free layer has a single-layer structure.

11. The magnetic memory element according to claim 1, wherein the thickness of the free layer is 0.6 nm or more and 1.5 nm or less.

12. The magnetic memory element according to claim 1, further comprising a heavy metal layer provided on the free layer, wherein the heavy metal layer contains at least one of Ir and Os.

13. The magnetic memory element according to claim 12, wherein the heavy metal layer is an Ir layer.

14. The magnetic memory element according to claim 12, wherein the thickness of the heavy metal layer is 0.05 nm or more and 0.25 nm.

15. The magnetic memory element according to claim 12, wherein the heavy metal layer comprises a first heavy metal layer located between the free layer and the barrier layer, and a second heavy metal layer located on the opposite side of the barrier layer from the free layer, and the thickness of the first heavy metal layer is 0.05 nm or more and 0.1 nm or less.

16. The magnetic memory element according to claim 1, further comprising a substrate, wherein the fixed layer is located between the substrate and the free layer.

17. The magnetic memory element according to claim 1, further comprising a substrate, wherein the free layer is located between the substrate and the fixed layer.

18. The magnetic memory element according to claim 1, further comprising a cap barrier layer located on the opposite side of the barrier layer from the free layer, wherein the cap barrier layer contains MgO.

19. The magnetic memory element according to claim 18, wherein the cap barrier layer comprises MgO and at least one of Fe, Co, Mn, V, and Ti.

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