Magnetic transfer charge-induced magnetic field sensor

Abstract

To provide a magnetic sensor capable of simultaneously satisfying demands for sensitivity, output, power consumption, and size.SOLUTION: A magnetic field sensor comprises a lamination structure in which a first electrode layer, a ferromagnetic / ferroelectric layer including a ferromagnetic / ferroelectric material with perpendicular magnetic anisotropy in which electric polarization having a perpendicular component is induced by application of a perpendicular magnetic field, and a soft magnetic layer including a soft magnetic material with perpendicular magnetic anisotropy are laminated in this order. The lamination structure includes a second electrode layer arranged so that the ferromagnetic / ferroelectric layer is sandwiched between the second electrode layer and the first electrode layer. When the soft magnetic layer is conductive, the soft magnetic layer may also serve as the second electrode layer, and the electric polarization induced in the ferromagnetic / ferroelectric layer is detected as an electric signal generated between the first electrode layer and the second electrode layer.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a novel magnetic field sensor capable of detecting a magnetic field as an electric signal. [Background technology]

[0002] To realize Society 5.0, numerous sensors must be deployed in physical space. Demand for magnetic field sensors to visualize position is sure to increase dramatically. Against this backdrop, there is a need for magnetic sensors that are highly sensitive, high-output, low-power, and miniaturizable. Tunneling magnetoresistive elements (MTEs) are currently attracting attention as a magnetic sensor that may be able to meet the sensitivity and size requirements. Tunneling magnetoresistive elements have a structure in which an electrically insulating thin film is sandwiched between two ferromagnetic layers. A voltage is applied between the two ferromagnetic layers to detect a tunneling current. The magnetization direction of one ferromagnetic layer (the pinned layer) is fixed, while the magnetization direction of the other ferromagnetic layer (the free layer) changes in response to an external magnetic field. When the magnetizations of the two ferromagnetic layers are aligned by an external magnetic field, the tunneling current increases (resistance decreases). When the magnetizations of the two ferromagnetic layers are aligned by an external magnetic field, the tunneling current decreases (resistance increases). Tunneling magnetoresistance elements recognize magnetic fields based on the magnitude of electrical resistance, taking advantage of the fact that the combination of magnetization directions (parallel / antiparallel) of the two magnetic layers changes depending on the direction of the external magnetic field, thereby changing the magnitude of the tunneling current. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5771788 [Patent Document 2] Patent No. 6573374 [Non-patent literature]

[0004] [Non-Patent Document 1] Yoshimura, S., et al., Magnetization reversal of [Co / Pd] perpendicular magnetic thin film dot on (Bi,La)(Fe,Co)O3 multiferroci thin film by applying electric field. Nanotechnology, 2003, 34(46), 465703. doi:10.1088 / 1361-6528 / acef2d Summary of the Invention [Problem to be solved by the invention]

[0005] Tunneling magnetoresistance elements are excellent in terms of sensitivity, as their resistance changes even with a slight magnetic field of a few Oe. However, they require a constant current to flow through the element, which consumes a lot of power. Furthermore, the ratio of the magnitude of the tunneling current to the small current is only about three times at room temperature, making the output ratio low and prone to detection errors.

[0006] To address the issues of power consumption and output ratio, those skilled in the art might consider applying the magnetoelectric effect of ferromagnetic and ferroelectric thin films to magnetic field sensors. Ferromagnetic and ferroelectric materials do not exhibit electric polarization in the absence of a magnetic field. However, when a magnetic field is sensed, electric polarization is induced due to the magnetoelectric effect (the interaction between a magnetic moment and an electric dipole). Therefore, a magnetic field sensor could be envisioned that includes a ferromagnetic and ferroelectric thin film sandwiched between two electrodes. Such a magnetic field sensor can reduce power consumption because it does not require a constant current flow. Furthermore, a high signal-to-output ratio can be achieved because the charge is induced from zero to a certain value. The problem with constructing such a magnetic field sensor using currently known typical ferromagnetic and ferroelectric thin films is that their magnetic field sensitivity is very poor. This is because currently known ferromagnetic and ferroelectric thin films generally have an in-plane easy magnetization direction and a large coercive force (several hundred Oe or more). Therefore, the magnetoelectric effect can only be achieved when a large magnetic field (several hundred Oe or more) is applied.

[0007] An object of the present invention is to provide a magnetic field sensor that can simultaneously satisfy the demands for sensitivity, output, power consumption, and size, and also to provide a magnetic field detection device that includes the magnetic field sensor. [Means for solving the problem]

[0008] The present invention includes the following embodiments [1] to [8]. [1] a first electrode layer; a ferromagnetic / ferroelectric layer comprising a ferromagnetic / ferroelectric material having perpendicular magnetic anisotropy, in which electric polarization having a perpendicular component is induced by application of a perpendicular magnetic field; a soft magnetic layer comprising a soft magnetic material having perpendicular magnetic anisotropy; A laminated structure including the following in the above order, The laminated structure is a second electrode layer, the second electrode layer being disposed so that the ferromagnetic-ferroelectric layer is sandwiched between the second electrode layer and the first electrode layer; Including, When the soft magnetic layer is conductive, the soft magnetic layer may also serve as the second electrode layer, A magnetic field sensor, characterized in that the electric polarization induced in the ferromagnetic-ferroelectric layer is detected as an electric signal generated between the first electrode layer and the second electrode layer.

[0009] [2] The laminated structure includes the second electrode layer separate from the soft magnetic layer, The magnetic field sensor according to [1], wherein the laminated structure includes, in the above order, the first electrode layer, the ferromagnetic-ferroelectric layer, the soft magnetic layer, and the second electrode layer.

[0010] [3] The laminated structure includes the second electrode layer separate from the soft magnetic layer, The magnetic field sensor according to [1], wherein the laminated structure includes, in the above order, the first electrode layer, the ferromagnetic-ferroelectric layer, the second electrode layer, and the soft magnetic layer.

[0011] [4] The saturation magnetization of the soft magnetic layer at 25°C is Ms1 (unit: emu / cm 3 ), the thickness of the soft magnetic layer is t1 (unit: nm), and the coercive force of the ferromagnetic and ferroelectric material at 25°C is Hc2 (unit: Oe), the ratio 4πMs1t1 / Hc2 is 1000 nm or more.

[0012] [5] Let Hc1 (unit: Oe) be the coercive force of the soft magnetic layer at 25°C, and Mr2 (unit: emu / cm) be the remanent magnetization of the ferromagnetic and ferroelectric material at 25°C. 3 ) the ratio 4πMr2t2 / Hc1 is less than 3000 nm.

[0013] [6] The magnetic field sensor according to any one of [1] to [5], wherein the ferromagnetic and ferroelectric layer contains a material represented by the following composition formula (2) and exhibits ferromagnetic and ferroelectric properties and perpendicular magnetic anisotropy: (Bi 1-a X a )(Fe 1-b M b )O3…(2) (In composition formula (2), X represents one or more elements selected from Mg, Ca, Sr, Ba, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu; M represents one or more elements selected from Ti, V, Cr, Mn, Co, Ni, Cu, and Zn; and a and b represent real numbers satisfying 0≦a≦0.8 and 0≦b≦0.5, with the proviso that at least one of a and b is not 0.)

[0014] [7] The magnetic field sensor according to any one of [1] to [6], wherein the soft magnetic conductive layer contains a soft magnetic material represented by the following composition formula (3): Co x Ni 1-x Fe2O4…(3) (In the composition formula (1), x is a real number of 0 to 0.8.)

[0015] [8] A magnetic field sensor according to any one of [1] to [7], a detection circuit electrically connected to the first electrode layer and the second electrode layer, for detecting the electric polarization induced in the ferromagnetic-ferroelectric layer as an electric signal; A magnetic field detection device comprising: [Effects of the Invention]

[0016] In the magnetic field sensor and magnetic field detection device of the present invention, a soft magnetic conductive layer containing a soft magnetic material with perpendicular magnetic anisotropy is magnetized by an external magnetic field, and a magnetic field generated from the interface (pole face) of the magnetized soft magnetic conductive layer facing the ferromagnetic-ferroelectric layer magnetizes the ferromagnetic-ferroelectric layer with perpendicular magnetic anisotropy. Electric polarization containing a perpendicular component is generated in the magnetized ferromagnetic-ferroelectric layer. This electric polarization can be detected as an electric signal between the first and second electrodes to detect an external magnetic field. Since a soft magnetic conductive layer containing a soft magnetic material, which is an easily magnetized ferromagnetic material, is stacked on a ferromagnetic-ferroelectric layer, sensitivity can be improved. Furthermore, since the electric polarization is detected as an electric signal, the output ratio can be increased. Furthermore, since an external voltage does not need to be constantly applied, power consumption can be reduced compared to conventional tunnel magnetoresistance elements. Furthermore, the stacked structure can be miniaturized using a lithography process. Therefore, the magnetic field sensor and magnetic field detection device of the present invention can simultaneously satisfy requirements for sensitivity, output, power consumption, and size. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a diagram illustrating a schematic configuration of a magnetic field sensor 10 and a magnetic field detection device 100 according to an embodiment of the present invention. [Figure 2]Fig. 2(A) is a diagram illustrating the magnetic field sensor 10 and the magnetic field detection device 100 in a state where no external magnetic field is applied and the soft magnetic layer 3 and the ferromagnetic-ferroelectric layer 2 are not magnetized. Fig. 2(B) is a diagram illustrating the operation of the magnetic field sensor 10 and the magnetic field detection device 100 when an external magnetic field Hext in the perpendicular direction is applied. Fig. 2(C) is a diagram illustrating the operation of the magnetic field sensor 10 and the magnetic field detection device 100 when an external magnetic field Hext' in the opposite direction is applied after the state of Fig. 2(B). [Figure 3] FIG. 10 is a diagram illustrating the configuration of a magnetic field sensor 210 and a magnetic field detection device 200 according to another embodiment. [Figure 4] Fig. 4(A) is a diagram illustrating a schematic configuration of a magnetic field sensor 310 and a magnetic field detection device 300 according to another embodiment. Fig. 4(B) is a diagram illustrating a schematic wiring method for connecting the second electrode layer 4 and the detection circuit 20 in the magnetic field sensor 310 and the magnetic field detection device 300. [Figure 5] Fig. 5(A) is a diagram illustrating the magnetic field sensor 310 and the magnetic field detection device 300 in a state where no external magnetic field is applied and the soft magnetic layer 303 and the ferromagnetic-ferroelectric layer 2 are not magnetized. Fig. 5(B) is a diagram illustrating the operation of the magnetic field sensor 310 and the magnetic field detection device 300 when an external magnetic field Hext in the perpendicular direction is applied. Fig. 5(C) is a diagram illustrating the operation of the magnetic field sensor 310 and the magnetic field detection device 300 when an external magnetic field Hext' in the opposite direction is applied after the state of Fig. 5(B). [Figure 6]6A is a diagram illustrating the magnetic field sensor 410 and the magnetic field detection device 400 in a state where a perpendicular external magnetic field Hext is applied to the magnetic field sensor 410, the soft magnetic layer 303 has a perpendicular magnetization M1 oriented in the same direction as the external magnetic field Hext, and the ferromagnetic-ferroelectric layer 402 has a perpendicular magnetization M2 oriented in the same direction as the magnetization M1. FIG. 6B is a diagram illustrating the magnetic field sensor 410 and the magnetic field detection device 400 at the moment when an external magnetic field Hext' oriented perpendicularly and opposite to the external magnetic field Hext is applied to the magnetic field sensor 410, and the magnetizations of the soft magnetic layer 3 and the ferromagnetic-ferroelectric layer 402 become in-plane magnetization during reversal. FIG. 6C is a diagram illustrating the magnetic field sensor 410 and the magnetic field detection device 400 in a state where the magnetization of the ferromagnetic-ferroelectric layer 402 has completely reversed after the state of FIG. 6B. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to these embodiments. The drawings do not necessarily reflect accurate dimensions. Some symbols may be omitted in the drawings. In addition, in Figure N (N is an integer of 2 or more), elements that have already appeared in Figures 1 to N-1 may be assigned the same symbols and their explanations may be omitted. In this specification, unless otherwise specified, the notation "A to B" for numerical values ​​A and B means "greater than or equal to A and less than or equal to B." In such notation, when a unit is assigned only to numerical value B, the unit also applies to numerical value A. Furthermore, the words "or" and "or" mean a logical sum unless otherwise specified. Furthermore, the notation "E1 and / or E2" for elements E1 and E2 means "E1 or E2, or a combination thereof," and the notation "E1 and / or E2" means "E1 or E2, or a combination thereof," and the notation "E1 and / or E2" means "E1 or E2, or a combination thereof," and the notation "E1, ..., E" means "E1 and / or E2." N (N is an integer greater than or equal to 3) for E1, ..., E N-1 , and / or E N " is written as "E1, ..., E N-1 , or E N or a combination thereof.”

[0019] FIG. 1 is a diagram illustrating the configuration of a magnetic field sensor 10 and a magnetic field detection device 100 according to one embodiment. The magnetic field detection device 100 includes the magnetic field sensor 10 and a detection circuit 20 electrically connected to the magnetic field sensor 10. The magnetic field sensor 10 has a layered structure in which a first electrode layer 1, a ferromagnetic-ferroelectric layer 2, a soft magnetic layer 3, and a second electrode layer 4 are layered in the above order. The second electrode layer 4 is disposed such that the ferromagnetic-ferroelectric layer 2 is sandwiched between the first electrode layer 1 and the second electrode layer 4. The detection circuit 20 is electrically connected to the first electrode layer 1 and the second electrode layer 4.

[0020] The first electrode layer 1 can be made of, for example, a non-magnetic (diamagnetic or paramagnetic) conductive material. Examples of conductive materials that can be used to make the first electrode layer 1 include Pt. The thickness of the first electrode layer 1 is not particularly limited, but can be, for example, 10 to 200 nm.

[0021] The ferromagnetic-ferroelectric layer 2 contains a ferromagnetic-ferroelectric material with perpendicular magnetic anisotropy, and electric polarization with a perpendicular component is induced by application of a perpendicular magnetic field.

[0022] For the ferromagnetic-ferroelectric layer 2, for example, a material expressed by the following composition formula (1) and exhibiting ferromagnetic-ferroelectric properties and perpendicular magnetic anisotropy can be used. (A x B 1-x ) l (N y M 1-y ) m O n …(1) (In composition formula (1), A and B each independently represent Bi, Pb, alkaline earth metals (Mg, Ca, Sr, Ba), lanthanoids (La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu), Y, Cr, or Co; M and N each independently represent Fe, Ti, V, Cr, Mn, Co, Ni, Cu, or Zn; x represents a real number from 0 to 1; y represents a real number from 0 to 1; l represents an integer from 1 to 3; m represents an integer from 1 to 3; and n represents an integer from 3 to 6.) Examples of materials represented by the compositional formula (1) that can exhibit ferromagnetism and ferroelectricity include, for example, TbMnO3, TbMn2O5, YMnO3, EuTiO3, CoCr2O4, Cr2O3, BiMn 0.5 Ni 0.5 O3, BiFe 0.5 Cr 0.5 O3, La 0.1 Bi 0.9 MnO3, La 1-x Bi x Ni 0.5 Mn 0.5 O3, Bi 1-x Ba x FeO3, etc. can be mentioned.

[0023] As a preferred example of the ferromagnetic and ferroelectric material constituting the ferromagnetic and ferroelectric layer 2, a material represented by the following compositional formula (2) and exhibiting ferromagnetic, ferroelectric, and perpendicular magnetic anisotropy can be mentioned. (Bi 1-a X a )(Fe 1-b M b )O3…(2) (In the compositional formula (2), X is one or more elements selected from alkaline earth metals (Mg, Ca, Sr, Ba) and lanthanoids (La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu); M is one or more elements selected from Ti, V, Cr, Mn, Co, Ni, Cu, or Zn; and a and b are real numbers satisfying 0 ≦ a ≦ 0.8 and 0 ≦ b ≦ 0.5. However, at least one of a and b is not 0.) In the compositional formula (2), it is preferable that a and b satisfy 0 < a ≦ 0.8 and 0 < b ≦ 0.5, and more preferably 0 < a ≦ 0.8, 0 < b ≦ 0.5, and 0.01 ≦ a + b ≦ 1.3. By substituting a part of Bi in BiFeO3, which is a known dielectric material, with the above-mentioned predetermined element X and a part of Fe with the above-mentioned predetermined element M, preferable ferromagnetism and ferroelectricity are exhibited. At this time, when the substitution rates a and b are within the above ranges, ferromagnetism and ferroelectricity particularly suitable for the operation of the magnetic field sensor 10 and the magnetic field detection device 100 are simultaneously exhibited. Examples of such materials include Bi(Fe,Mn)O3, (Bi,Ba)FeO3, (Bi,Ba,La)(Fe,Mn)O3, (Bi,Ba,La)(Fe,Mn,Ti)O3, (Bi,La)FeO3, (Bi,Nd)(Fe,Ni)O3, etc. More specifically, Bi(Fe 0.95 Mn 0.05 )O3, (Bi 0.8 Ba 0.2 )FeO3, (Bi 0.5 Ba 0.3 La 0.2 )FeO3, (Bi 0.7 La 0.3 )(Fe 0.7 Mn 0.3 )O3, (Bi 0.5 Ba 0.3 La 0.2 )(Fe 0.7 Mn 0.1 Ti 0.2 )O3, (Bi 0.5 Nd 0.5 )(Fe 0.7 Co 0.3 )O3, etc. Among the materials represented by composition formula (2), a (Bi,Nd)(Fe,Ni)O3-based material in which X is Nd and M is Ni can be particularly preferably used.

[0024] The thickness of the ferromagnetic-ferroelectric layer 2 is not particularly limited, but may be, for example, 20 to 200 nm, or 50 to 200 nm, or 20 to 100 nm. However, it is preferable that the thickness of the ferromagnetic-ferroelectric layer 2 satisfies the relationship described below.

[0025] The soft magnetic layer 3 is made of a soft magnetic material having perpendicular magnetic anisotropy. The soft magnetic material may be conductive or electrically insulating (dielectric). The soft magnetic layer 3 may consist of a single layer or may include multiple layers.

[0026] A preferred example of the soft magnetic material that constitutes the soft magnetic layer 3 is a soft magnetic material represented by the following composition formula (3). Cox Ni 1-x Fe2O4…(3) In the composition formula (3), x is a real number of 0 to 0.8, preferably 0 to 0.5. x Ni 1-x Fe2O4 is a soft magnetic material with perpendicular magnetic anisotropy, and has a low coercive force of, for example, 100 Oe or less at 25°C and a magnetic field strength of, for example, 500 emu / cm 3 It is possible to obtain a high saturation magnetization and a high Curie temperature.

[0027] Another example of the soft magnetic material for forming the soft magnetic layer 3 is [Co / Pt] n Multilayer films, such as those in which multiple Co layers and multiple paramagnetic metal layers are alternately stacked [Co / Q] n Examples include laminated films (wherein Q is one or more paramagnetic metal elements, preferably one or more metal elements selected from Pd, Pt, and Ir; and n is an integer of 2 or more, preferably 3 or more); and RE-TM (rare earth-transition metal) alloy-based soft magnetic materials such as Gd-Fe alloy, Gd-Co alloy, Gd-Fe-Co alloy, Tb-Fe alloy, Tb-Co alloy, Tb-Fe-Co alloy, Dy-Fe alloy, Dy-Co alloy, and Dy-Fe-Co alloy.

[0028] The thickness of the soft magnetic layer 3 is not particularly limited, and may be, for example, 20 to 500 nm, or 50 to 500 nm, or 100 to 500 nm. However, the thickness of the soft magnetic layer 3 preferably satisfies the relationship described below. In one embodiment, the thickness of the soft magnetic layer 3 is preferably equal to or greater than the thickness of the ferromagnetic-ferroelectric layer 2, or preferably greater than the thickness of the ferromagnetic-ferroelectric layer 2, and may be, for example, at least twice the thickness of the ferromagnetic-ferroelectric layer 2.

[0029] The magnetization M1 (unit: emu / cm) of the soft magnetic layer 3 3) that the ferromagnetic-ferroelectric layer 2 receives is theoretically at most 4πM1 (unit: Oe), and the thicker the soft magnetic layer 3 is than the ferromagnetic-ferroelectric layer 2, the closer the magnetic field approaches this upper limit. In this specification, π represents the constant pi. From the viewpoint of magnetizing the ferromagnetic-ferroelectric layer 2 with the magnetic field generated from the soft magnetic layer 3, the saturation magnetization Ms1 (unit: emu / cm) of the soft magnetic material that constitutes the soft magnetic layer 3 at 25°C is 3 ), the thickness t1 (unit: nm) of the soft magnetic layer 3, and the coercive force Hc2 (unit: Oe) at 25°C of the ferromagnetic-ferroelectric material constituting the ferromagnetic-ferroelectric layer 2, it is preferable that the value of the ratio r1=4πMs1t1 / Hc2 (unit: nm) be 1000 nm or more, or 1500 nm or more, or 2000 nm or more. The inventor has experimentally determined that the thickness t 01 =200nm, saturation magnetization Ms 01 =80emu / cm 3 The magnetization induced in the first ferromagnetic layer causes a layer of thickness t 02 =10nm, coercive force Hc 02 =300emu / cm 3 They have succeeded in writing magnetization into the second ferromagnetic layer of 4πMs (Non-Patent Document 1). 01 t 01 / Hc 02 The value (unit: nm) is calculated to be 2009.6 nm.

[0030] The remanent magnetization Mr2 (unit: emu / cm) of the ferromagnetic and ferroelectric layers 2 3 ) that the soft magnetic layer 3 receives from the ferromagnetic-ferroelectric layer 2 does not theoretically exceed 4πMr2 (unit: Oe), but if the thickness of the ferromagnetic-ferroelectric layer 2 is smaller than the thickness of the soft magnetic layer 3, the magnetic field will be even smaller. From the viewpoint of making it easier to demagnetize or reverse the magnetization of the ferromagnetic-ferroelectric layer 2 even when the external magnetic field is weak, the remanent magnetization Mr2 (unit: emu / cm) of the ferromagnetic-ferroelectric material constituting the ferromagnetic-ferroelectric layer 2 at 25°C should be set to 4πMr2 (unit: Oe). 3), the thickness t2 (unit: nm) of the ferromagnetic-ferroelectric layer 2, and the coercive force Hc1 (unit: Oe) at 25°C of the soft magnetic material constituting the soft magnetic layer 3, the ratio r2=4πMr2t2 / Hc1 (unit: nm) is preferably less than 3000 nm, or less than 2500 nm, or less than 2000 nm, and may be, for example, less than 1000 nm or less than 500 nm.

[0031] For example combinations of various values ​​of the thickness t1, saturation magnetization Ms1 at 25°C, and coercive force Hc1 at 25°C of the soft magnetic layer 3, and the thickness t2, remanent magnetization Mr2 at 25°C, and coercive force Hc2 at 25°C of the ferromagnetic / ferroelectric layer 2, the values ​​of the two ratios r1=4πMs1t1 / Hc2 and r2=4πMr2t2 / Hc1 are shown in Table 1 below. However, the present invention is not limited to these specific values.

[0032] [Table 1]

[0033] As can be seen from Table 1, when the soft magnetic layer 3 is thinner than the ferromagnetic-ferroelectric layer 2 (Nos. 1 to 6), it is not necessarily easy to set the values ​​of the two ratios r1=4πMs1t1 / Hc2 and r2=4πMr2t2 / Hc1 within the above-mentioned preferred ranges, even if the soft magnetic layer 3 has a relatively large saturation magnetization. In contrast, when the soft magnetic layer 3 is thicker than the ferromagnetic-ferroelectric layer 2, the ratio r1 tends to be a more preferred value even if the saturation magnetization of the soft magnetic layer 3 is relatively small or the coercive force of the ferromagnetic-ferroelectric layer 2 is relatively large, and the ratio r2 tends to be a more preferred value even if the remanent magnetization of the ferromagnetic-ferroelectric layer 2 is relatively large.

[0034] In one embodiment, from the viewpoint of making it easier to magnetize the ferromagnetic-ferroelectric layer 2 by the magnetic field generated from the soft magnetic layer 3, the coercive force of the ferromagnetic-ferroelectric layer 2 at 25° C. may be, for example, 1000 Oe or less, or 500 Oe or less. The lower limit of the coercive force of the ferromagnetic-ferroelectric layer 2 at 25° C. is not particularly limited, but may be greater than 0 Oe, for example, 100 Oe or more.

[0035] In one embodiment, from the viewpoint of making it easier to magnetize the ferromagnetic-ferroelectric layer 2 with the magnetic field generated from the soft magnetic layer 3, the saturation magnetic field of the ferromagnetic-ferroelectric layer 2 at 25°C may be preferably, for example, 1500 Oe or less, or 750 Oe or less. The saturation magnetic field of the ferromagnetic-ferroelectric layer 2 at 25°C is not particularly limited, but may be greater than 0 Oe, for example, 150 Oe or more.

[0036] In one embodiment, from the viewpoint of making it easier to magnetize the ferromagnetic-ferroelectric layer 2 with the magnetic field generated from the soft magnetic layer 3, the remanence magnetization of the ferromagnetic-ferroelectric layer 2 at 25° C. is preferably, for example, 50 emu / cm 3 or less, or 25 emu / cm 3 The lower limit of the remanent magnetization of the ferromagnetic-ferroelectric layer 2 at 25° C. is not particularly limited, but it is preferably 0 emu / cm 3 Larger, e.g., 10 emu / cm 3 It could be more than that.

[0037] In one embodiment, from the viewpoint of further increasing the sensitivity of the magnetic field sensor 10 and the magnetic field detection device 100, the coercive force of the soft magnetic layer 3 at 25° C. may be, for example, 100 Oe or less, or 50 Oe or less, or 25 Oe or less. The lower limit of the coercive force of the soft magnetic layer 3 at 25° C. is not particularly limited, but may be greater than 0 Oe, for example, 10 Oe or more.

[0038] In one embodiment, from the viewpoint of facilitating magnetization of the ferromagnetic-ferroelectric layer 2, the saturation magnetization of the soft magnetic layer 3 at 25° C. is preferably, for example, 300 emu / cm 3or more than 500 emu / cm 3 or more than 700 emu / cm 3 The upper limit of the saturation magnetization of the soft magnetic layer 3 at 25° C. is not particularly limited, but may be, for example, 1000 emu / cm 3 It can be the following:

[0039] In one embodiment, from the viewpoint of enhancing the detection sensitivity of the magnetic field, the saturation magnetic field of the soft magnetic layer 3 at 25° C. is preferably, for example, 150 Oe or less, or 75 Oe or less. The lower limit of the saturation magnetic field of the soft magnetic layer 3 at 25° C. is not particularly limited, but may be greater than 0 Oe, for example, 15 Oe or more.

[0040] The second electrode layer 4 forms a capacitor together with the first electrode layer 1. In other words, the second electrode layer 4 is an opposing electrode to the first electrode layer 1. The second electrode layer 4 can be made of, for example, a non-magnetic (diamagnetic or paramagnetic) conductive material. An example of the conductive material that can be used to make the second electrode layer 4 is Pt. The thickness of the second electrode layer 4 is not particularly limited, but can be, for example, 10 to 200 nm.

[0041] In one preferred embodiment, the magnetic field sensor 10 can be fabricated by, for example, growing a first electrode layer 1, a ferromagnetic-ferroelectric layer 2, a soft magnetic layer 3, and a second electrode layer 4 in this order on the surface of a nonmagnetic substrate. In another embodiment, the magnetic field sensor 10 can be fabricated by, for example, growing a second electrode layer 4, a soft magnetic layer 3, a ferromagnetic-ferroelectric layer 2, and a first electrode layer 1 in this order on the surface of a nonmagnetic substrate. The substrate can be made of, for example, Si. The first electrode layer 1, the second electrode layer 4, and the soft magnetic layer 3 can be grown by vapor deposition, such as sputtering. The ferromagnetic-ferroelectric layer 2 can be grown by vapor deposition, such as reactive pulse DC sputtering.

[0042] The detection circuit 20 is electrically connected to the soft magnetic layer 3 and the first electrode layer 1. It detects the electric polarization induced in the ferromagnetic-ferroelectric layer 2 as an electric signal and outputs the result as a logic value. The detection circuit 20 may include, for example, an amplifier circuit with high input impedance and a level determination circuit. Such a detection circuit 20 may be configured using known circuit technology (e.g., a differential amplifier circuit with FET (field-effect transistor) input, a comparator circuit, etc.). In one embodiment, the output of the detection circuit 20 may be, for example, a binary value (e.g., logical values ​​"1 (H)" and "0 (L)") or a ternary value (e.g., logical values ​​"+1", "0", and "-1"). In one embodiment, the detection circuit 20 may include a differentiation circuit and a bit storage circuit provided downstream of the differentiation circuit, which inverts the logic value each time the differentiation circuit outputs a pulse having an absolute value equal to or greater than a predetermined value. When the magnetization reversal of the ferromagnetic-ferroelectric layer 2 occurs, the potential difference between the first electrode 1 and the second electrode 4 changes abruptly. This abrupt change, when passed through a differential filter, becomes a pulse. By detecting this pulse, the magnetization reversal of the ferromagnetic-ferroelectric layer 2 can be detected more accurately. When the differential circuit outputs a pulse having an absolute value equal to or greater than a predetermined value, if the logic value held by the bit storage circuit is H(+1), the logic value held by the bit storage circuit changes to L(0). Similarly, if the logic value held by the bit storage circuit is L(0), the logic value held by the bit storage circuit changes to H(+1). Such a bit storage circuit can be configured using, for example, a flip-flop circuit or a latch circuit. If necessary, a circuit may be further provided that inputs a predetermined pulse of logic H or L to the bit storage circuit each time the differential circuit outputs a pulse having an absolute value equal to or greater than a predetermined value. A circuit having such a function may be configured, for example, to include a pulse generating circuit capable of outputting a pulse of a predetermined logic value (H or L), and a trigger circuit that monitors the output of the differentiating circuit and causes the pulse generating circuit to generate a pulse of the predetermined logic value when it detects that the absolute value of the output of the differentiating circuit exceeds a predetermined value. The detection circuit 20 further including such a bit memory circuit can hold the output logic value of the detection circuit 20 until the direction of the external magnetic field is next reversed and the magnetizations of the soft magnetic layer 3 and the ferromagnetic-ferroelectric layer 2 are reversed.For example, even if the potential difference between the first electrode and the second electrode gradually decreases toward zero while the magnetization of the ferromagnetic-ferroelectric layer 2 maintains its direction, it becomes easy to maintain the output logic value of the detection circuit 20 until the next time the magnetization of the ferromagnetic-ferroelectric layer 2 reverses.

[0043] 2A to 2C are diagrams illustrating the operation of the magnetic field sensor 10 and magnetic field detection device 100 according to one embodiment. FIG. 2A shows a state in which no external magnetic field is applied and the soft magnetic layer 3 and the ferromagnetic-ferroelectric layer 2 are not magnetized. In this state, no electric polarization occurs in the ferromagnetic-ferroelectric layer 2, and therefore no potential difference occurs between the first electrode layer 1 and the second electrode layer 4, which form a capacitor with the ferromagnetic-ferroelectric layer 2 sandwiched therebetween. Therefore, in this state, the potential difference (between the first electrode layer 1 and the second electrode layer 4) input to the detection circuit 20 is zero. The detection circuit 20 outputs a logical value "0" (e.g., a voltage of 0 V) ​​based on the level determination.

[0044] Figure 2(B) shows the vertical external magnetic field H ext In this specification, the terms "perpendicular direction" and "perpendicular component" refer to the direction and component perpendicular to the in-plane direction of the soft magnetic layer 3 and the ferromagnetic-ferroelectric layer 2, respectively. ext When a magnetic field H is applied, the soft magnetic layer 3 having perpendicular magnetic anisotropy is magnetized in the perpendicular direction, generating a magnetization M1. At the interface (pole surface) between the soft magnetic layer 3 and the ferromagnetic-ferroelectric layer 2, a perpendicular magnetic field of up to 4πM1 is generated by the magnetization M1 of the soft magnetic layer 3. This perpendicular magnetic field is usually generated by the external magnetic field H extThis strong perpendicular magnetic field 4πM1 magnetizes the ferromagnetic-ferroelectric layer 2, which has perpendicular magnetic anisotropy, in the perpendicular direction, generating magnetization M2, and also induces electric polarization P2 with a perpendicular component in a predetermined direction relative to magnetization M2. In this state, electric polarization P2 with a perpendicular component is generated in the ferromagnetic-ferroelectric layer 2, and a potential difference is generated between the first electrode layer 1 and the second electrode layer 4, which form a capacitor with the ferromagnetic-ferroelectric layer 2 sandwiched between them. Therefore, the potential difference (between the first electrode layer 1 and the second electrode layer 4) input to the detection circuit 20 is a non-zero value V. The detection circuit 20 outputs a logical value "+1" (e.g., a voltage of +5V) based on the level determination. In one embodiment, from the viewpoint of facilitating magnetization of the ferromagnetic-ferroelectric layer 2 by causing an interaction between the magnetic moment of the soft magnetic layer 3 and the magnetic moment of the ferromagnetic-ferroelectric layer 2 at the interface between the soft magnetic layer 3 and the ferromagnetic-ferroelectric layer 2, it is preferable that the soft magnetic layer 3 and the ferromagnetic-ferroelectric layer 2 are laminated in direct physical contact with each other.

[0045] Figure 2(C) shows the state after Figure 2(B) when an external magnetic field H ext 1 is a diagram for explaining the operation when an external magnetic field H′ is applied. ext When external magnetic field H is applied, the magnetization M1 of the soft magnetic layer 3 is reversed to magnetization M1'. Again, at the interface (pole surface) between the soft magnetic layer 3 and the ferromagnetic-ferroelectric layer 2, a perpendicular magnetic field of up to 4πM1' is generated by the magnetization M1' of the soft magnetic layer 3. This perpendicular magnetic field is usually extThis strong perpendicular magnetic field 4πM1' reverses the magnetization M2 of the ferromagnetic-ferroelectric layer 2 to M2', and also reverses the direction of the electric polarization P2 to P2'. In this state, the direction of the electric polarization of the ferromagnetic-ferroelectric layer 2 is reversed, so the polarity of the potential difference generated between the first electrode layer 1 and the second electrode layer 4, which form a capacitor sandwiching the ferromagnetic-ferroelectric layer 2, is also reversed. Therefore, the potential difference (between the first electrode layer 1 and the second electrode layer 4) input to the detection circuit 20 is a value -V' with the opposite sign to that in the state of Figure 2(B) (i.e., V × (-V') < 0). The detection circuit 20 outputs a logical value "-1" (e.g., a voltage of -5V) based on the level determination. In one embodiment, from the viewpoint of facilitating magnetization reversal of the ferromagnetic-ferroelectric layer 2 by causing an interaction between the magnetic moment of the soft magnetic layer 3 and the magnetic moment of the ferromagnetic-ferroelectric layer 2 at the interface between the soft magnetic layer 3 and the ferromagnetic-ferroelectric layer 2, it is preferable that the soft magnetic layer 3 and the ferromagnetic-ferroelectric layer 2 are laminated in direct physical contact with each other.

[0046] According to the magnetic field sensor 10 and magnetic field detection device 100 of the present invention, even a weak external magnetic field causes the soft magnetic layer 3 to be magnetized or its magnetization reversed. The magnetization of the soft magnetic layer 3 magnetizes or reverses the magnetization of the ferromagnetic-ferroelectric layer 2 through exchange interaction, magnetostatic interaction, or both, and also induces electric polarization in the ferromagnetic-ferroelectric layer 2, thereby improving the sensitivity of magnetic field detection. Furthermore, because the induced electric polarization is detected as an electric signal, there is no need to apply a DC voltage to the magnetic field sensor 10 from an external source, thereby reducing power consumption. Furthermore, because the electric polarization of the ferromagnetic-ferroelectric layer 2 is zero, a predetermined non-zero value, or a predetermined value of the opposite polarity, the output ratio can be increased, which contributes to reducing the read error rate. Furthermore, because the soft magnetic layer 3 and the ferromagnetic-ferroelectric layer 2 have perpendicular magnetic anisotropy and are magnetized in the perpendicular direction, the magnetic field sensor can be suitable for applications such as IoT (Internet of Things).

[0047] In the above description of the present invention, the magnetic field detection device 100 is exemplified as one in which the output of the detection circuit 20 is a logical ternary value, but the present invention is not limited to this. For example, it is also possible to define either the state of Fig. 2(B) or Fig. 2(C) as "0" and to provide a magnetic field detection device in which the output is a logical 2 value.

[0048] In the above description of the present invention, the magnetic field sensor 10 and the magnetic field detection device 100 are exemplified, in which an electric polarization P2 in the same direction as the magnetization M2 is induced in the ferromagnetic-ferroelectric layer 2. However, the present invention is not limited to this configuration. For example, a ferromagnetic-ferroelectric material in which an electric polarization in the opposite direction (antiparallel) to the magnetization may be used for the ferromagnetic-ferroelectric layer. Also, for example, a ferromagnetic-ferroelectric material in which an electric polarization in a direction tilted relative to the magnetization may be used for the ferromagnetic-ferroelectric layer.

[0049] In the above description of the present invention, the magnetic field sensor 10 and the magnetic field detection device 100 are described as having a second electrode layer 4 separate from the soft magnetic layer 3. However, the present invention is not limited to this configuration. For example, if the soft magnetic layer 3 is conductive, the conductive soft magnetic layer 3 also functions as a counter electrode for the first electrode layer 1. Therefore, the conductive soft magnetic layer 3 may also serve as the second electrode layer without providing a second electrode layer 4 separate from the soft magnetic layer 3. FIG. 3 is a diagram schematically illustrating the configuration of a magnetic field sensor 210 and a magnetic field detection device 200 according to another embodiment. The magnetic field detection device 200 includes the magnetic field sensor 210 and a detection circuit 20. The magnetic field sensor 210 has a layered structure including, in this order, a first electrode layer 1, a ferromagnetic-ferroelectric layer 2, and a conductive soft magnetic layer 203. The conductive soft magnetic layer 203 also serves as the second electrode layer, and together with the first electrode layer 1, the ferromagnetic-ferroelectric layer 2 is sandwiched between them to form a capacitor. One input terminal of the detection circuit 20 is connected to the first electrode layer 1, and the other input terminal of the detection circuit 20 is connected to the conductive soft magnetic layer 3. The magnetic field sensor 210 and the magnetic field detection device 200 having such a configuration can also achieve the same effects as those described above. Furthermore, when the soft magnetic layer 3 includes a conductive layer, the conductive layer also functions as an opposing electrode for the first electrode layer 1. Therefore, the conductive layer included in the soft magnetic layer 3 may also serve as the second electrode layer without providing a second electrode layer 4 separate from the soft magnetic layer 3. That is, an input terminal of a detection circuit 20 (described later) may be connected to the first electrode layer 1, and the other input terminal of the detection circuit 20 may be connected to the conductive layer included in the soft magnetic layer 3. When the conductive layer is not exposed on the surface of the soft magnetic layer 3, the conductive layer may be partially exposed by a processing method such as a photolithography process or ion etching.

[0050] In the above description of the present invention, the magnetic field sensor 10 and the magnetic field detection device 100 have been described as having a laminated structure in which a first electrode layer 1, a ferromagnetic-ferroelectric layer 2, a soft magnetic layer 3, and a second electrode layer 4 are laminated in this order. However, the present invention is not limited to this configuration. For example, the magnetic field sensor and the magnetic field detection device may have a structure in which a second electrode layer is disposed between the ferromagnetic-ferroelectric layer 2 and the soft magnetic layer 3. FIG. 4A is a diagram schematically illustrating the configuration of a magnetic field sensor 310 and a magnetic field detection device 300 according to another embodiment. The magnetic field detection device 300 includes a magnetic field sensor 310 and a detection circuit 20. The magnetic field sensor 310 has a laminated structure in which a first electrode layer 1, a ferromagnetic-ferroelectric layer 2, and a soft magnetic layer 303 are laminated in this order. The laminated structure further includes a second electrode layer 304 disposed between the ferromagnetic-ferroelectric layer 2 and the soft magnetic layer 303. The second electrode layer 304 and the first electrode layer 1 sandwich the ferromagnetic-ferroelectric layer 2 to form a capacitor.

[0051] The soft magnetic layer 303 is similar to the soft magnetic layer 3 (see FIGS. 1 and 2) described above in relation to the magnetic field sensor 10 and the magnetic field detection device 100, except that holes 303h are provided in parts of the soft magnetic layer 303, and the second electrode layer 304 is exposed in the holes 303h, in order to connect the second electrode layer 304 to the detection circuit 20. Providing the holes 303h in parts of the soft magnetic layer 303 so as to expose the second electrode layer 304 can be performed by a known processing method such as a photolithography process or ion etching.

[0052] The second electrode layer 304 can be made of the same material as the second electrode layer 4 (FIGS. 1 and 2) described above in relation to the magnetic field sensor 10 and the magnetic field detection device 100. From the viewpoint of making it easier to magnetize or reverse the magnetization of the ferromagnetic-ferroelectric layer 2 by the magnetization of the soft magnetic layer 303, the thickness of the second electrode layer 304 is preferably relatively thin, and may be, for example, 10 nm or less, or 5 nm or less. The lower limit of the thickness of the second electrode layer 304 is not particularly limited, but may be, for example, 1 nm or more, or 3 nm or more.

[0053] One terminal of the detection circuit 20 is electrically connected to the first electrode 1, and the other terminal of the detection circuit 20 is electrically connected to the second electrode layer 304. In one embodiment, the second electrode layer 304 can be connected to the detection circuit 20 by directly connecting wiring to the second electrode layer 304 through the hole 303h in the soft magnetic layer 303. In another embodiment, as shown in FIG. 4(B), the hole 303h in the soft magnetic layer 303 is filled with a conductive material (e.g., a diamagnetic or paramagnetic metal material), thereby forming a via 305 in the hole 303h that is electrically connected to the second electrode layer 304, and the second electrode layer 304 can be connected to the detection circuit 20 through the via 305.

[0054] 5A to 5C are diagrams illustrating the operation of a magnetic field sensor 310 and a magnetic field detection device 300 according to one embodiment. FIG. 5A shows a state in which no external magnetic field is applied and the soft magnetic layer 303 and the ferromagnetic-ferroelectric layer 2 are not magnetized. In this state, no electric polarization occurs in the ferromagnetic-ferroelectric layer 2, and therefore no potential difference occurs between the first electrode layer 1 and the second electrode layer 304, which form a capacitor with the ferromagnetic-ferroelectric layer 2 sandwiched therebetween. Therefore, in this state, the potential difference input to the detection circuit 20 is zero. The detection circuit 20 outputs a logical value "0" based on the level determination.

[0055] Figure 5(B) shows the vertical external magnetic field H ext 1 is a diagram for explaining the operation when an external magnetic field H ext When a magnetic field H is applied, the soft magnetic layer 303 having perpendicular magnetic anisotropy is magnetized in the perpendicular direction, generating a magnetization M1. On the surface (pole surface) of the soft magnetic layer 303 facing the ferromagnetic-ferroelectric layer 2, a perpendicular magnetic field of up to 4πM1 is generated by the magnetization M1 of the soft magnetic layer 303. This perpendicular magnetic field is usually generated by the external magnetic field H ext This strong perpendicular magnetic field 4πM1 magnetizes the ferromagnetic-ferroelectric layer 2, which has perpendicular magnetic anisotropy, in the perpendicular direction, generating magnetization M2, and also induces electric polarization P2 with a perpendicular component in a predetermined direction relative to magnetization M2. In this state, because electric polarization P2 with a perpendicular component is generated in the ferromagnetic-ferroelectric layer 2, a potential difference is generated between the first electrode layer 1 and the second electrode layer 304, which form a capacitor with the ferromagnetic-ferroelectric layer 2 sandwiched between them. Therefore, the potential difference input to the detection circuit 20 becomes a non-zero value V. The detection circuit 20 outputs a logical value "+1" based on the level determination.

[0056] Figure 5(C) shows the state after Figure 5(B) when an external magnetic field H ext 1 is a diagram for explaining the operation when an external magnetic field H′ is applied. extWhen external magnetic field H is applied, the magnetization M1 of the soft magnetic layer 303 is reversed to magnetization M1'. Again, on the surface (pole surface) of the soft magnetic layer 303 facing the ferromagnetic-ferroelectric layer 2, a perpendicular magnetic field of 4πM1' at maximum is generated by the magnetization M1' of the soft magnetic layer 303. This perpendicular magnetic field is usually ext This strong perpendicular magnetic field 4πM1' reverses the magnetization M2 of the ferromagnetic-ferroelectric layer 2 to M2', and also reverses the direction of the electric polarization P2 to P2'. In this state, the direction of the electric polarization of the ferromagnetic-ferroelectric layer 2 is reversed, so the polarity of the potential difference generated between the first electrode layer 1 and the second electrode layer 304, which form a capacitor with the ferromagnetic-ferroelectric layer 2 sandwiched between them, is also reversed. Therefore, the potential difference input to the detection circuit 20 becomes a value -V' with the opposite sign to that in the state of FIG. 5(B) (i.e., V×(-V')<0). The detection circuit 20 outputs a logical value "-1" based on the level determination.

[0057] The magnetic field sensor 310 and magnetic field detection device 300 having such a configuration can also provide the same effects as described above. According to this embodiment, since the distance between the first electrode layer 1 and the second electrode layer 304, which sandwich the ferromagnetic-ferroelectric layer 2 to form a capacitor, is short, it is possible to detect the electric polarization of the ferromagnetic-ferroelectric layer 2 with higher sensitivity.

[0058] In the above description of the present invention, magnetic field sensors 10, 210, 310 and magnetic field detection devices 100, 200, 300 have been described as including a ferromagnetic-ferroelectric layer 2 whose electric polarization direction reverses when its magnetization is reversed. However, the present invention is not limited to this configuration. The ferromagnetic-ferroelectric layer 2 described above is a ferromagnetic-ferroelectric layer that is significantly more stable when the magnetization and electric polarization directions are parallel (same direction) than when they are antiparallel. For example, instead of such a ferromagnetic-ferroelectric layer 2, a magnetic field sensor and a magnetic field detection device may be provided that includes a ferromagnetic-ferroelectric layer that is stable both when the magnetization and electric polarization directions are parallel (same direction) and antiparallel. FIGS. 6A to 6C are diagrams schematically illustrating the configuration and operation of a magnetic field sensor 410 and a magnetic field detection device 400 according to another embodiment. The magnetic field detection device 400 differs from the magnetic field detection device 100 (see FIGS. 1 and 2) described above in that it includes a magnetic field sensor 410 instead of the magnetic field sensor 10, and a detection circuit 420 instead of the detection circuit 20. The magnetic field sensor 410 differs from the magnetic field sensor 10 (see FIGS. 1 and 2) described above in that it includes a ferromagnetic-ferroelectric layer 402 instead of the ferromagnetic-ferroelectric layer 2. The ferromagnetic-ferroelectric layer 402 differs from the ferromagnetic-ferroelectric layer 2 (see FIGS. 1 and 2) in that it is stable both in a state where the magnetization direction and the electric polarization direction are parallel (same direction) and in a state where the magnetization direction and the electric polarization direction are antiparallel. FIG. 6(A) shows the magnetic field detection device 100 when an external magnetic field H ext is applied, and the soft magnetic layer 303 is subjected to an external magnetic field H ext 1 shows a state in which first electrode layer 1 has perpendicular magnetization M1 oriented in the same direction as magnetization M1, and ferromagnetic-ferroelectric layer 402 has perpendicular magnetization M2 oriented in the same direction as magnetization M1. In this state, electric polarization P2 is generated in ferromagnetic-ferroelectric layer 402, and potential difference V generated between first electrode layer 1 and second electrode layer 4 is input to detection circuit 402, which then outputs a logical value "+1."

[0059] 6B and 6C show the state after the state of FIG. 6A, in which an external magnetic field H ext6(B) is a diagram for explaining the operation when an external magnetic field H ext By applying the voltage ', the magnetization M1 of the soft magnetic layer 3 is reversed, and the in-plane magnetization M1 ip The magnetization M1 of the soft magnetic layer 3 ip The magnetization M2 of the ferromagnetic-ferroelectric layer 402 is changed to the in-plane magnetization M2 ip At this time, the electric polarization of the ferromagnetic-ferroelectric layer 402 also changes in the in-plane direction (magnetization M2 ip Electric polarization P2 parallel (co-direction) or anti-parallel to ipand the vertical component (film thickness direction component) of the electric polarization of the ferromagnetic / ferroelectric layer 402 becomes zero once. In this state, no potential difference occurs between the first electrode layer 1 and the second electrode layer 4, so the detection circuit 402 outputs a logical value "0". Note that the phenomenon itself in which the vertical component (film thickness direction component) of the electric polarization becomes zero while the magnetization of the ferromagnetic / ferroelectric layer reverses as described above also occurs in the magnetic field sensors 10, 210, 310 and the magnetic field detection devices 100, 200, 300 described above. Further, referring to FIG. 6(C), after FIG. 6(B), the magnetizations of the soft magnetic layer 3 and the ferromagnetic / ferroelectric layer 402 are completely reversed, and the magnetization of the ferromagnetic / ferroelectric layer 402 becomes the vertical magnetization M2' in the same direction as the magnetization M1' of the soft magnetic layer 3. The electric polarization of the ferromagnetic / ferroelectric layer 402 that was in the in-plane direction (i.e., the vertical component (film thickness direction component) is zero) becomes the electric polarization P2'' in the vertical direction (film thickness direction). The electric polarization P2'' may be in the opposite direction (anti-parallel) to the electric polarization P2 in FIG. 6(A), or may be in the same direction as the polarization P2 as shown in FIG. 6(C). Due to the electric polarization P2'' induced in the ferromagnetic / ferroelectric layer 402, a potential difference V'' of the same sign (i.e., V×V''>0; when the polarization P2'' is in the same direction as the polarization P2) or a different sign (i.e., V×V''<0; when the polarization P2'' is in the opposite direction to the polarization P2) to the potential difference V occurs between the first electrode layer 1 and the second electrode layer 4. When the potential differences V and V'' are of the same sign (i.e., the vertical component of the polarization P2'' is in the same direction as the vertical component of the polarization P2), the magnitudes of the potential differences V and V'' may be the same (i.e., V = V''; i.e., the vertical component of the polarization P2'' has the same magnitude as the vertical component of the polarization P2) or different from each other (i.e., V≠V''; i.e., the vertical component of the polarization P2'' has a different magnitude from the vertical component of the polarization P2), but it is preferable that they are different from each other. In the case of FIG. 6(C), the potential difference V'' is input to the detection circuit 420, and the detection circuit 420 outputs the logical value "+1" again. However, as described above, when the external magnetic field H ext ' is applied, the detection circuit 402 outputs a logical value "0". By detecting the change in the output value of the detection circuit 420, it is possible to detect that an external magnetic field H ext ' opposite to the magnetizations M1 of the soft magnetic layer 3 and M2 of the ferromagnetic / ferroelectric layer 402 has been applied.

[0060] The magnetization reversal and the change in the electric polarization strength of the ferromagnetic-ferroelectric layer 402 in FIGS. 6A to 6C occur in a very short time. The detection circuit 420 can easily detect the occurrence of the magnetization reversal by detecting that the electric polarization of the ferromagnetic-ferroelectric layer 402 temporarily becomes zero in FIG. 6B. In one embodiment, the detection circuit 420 may include a differentiation circuit (differential filter) and a pulse detection circuit for such detection. Because the magnetization reversal and the change in the electric polarization strength of the ferromagnetic-ferroelectric layer 402 occur in a very short time, the output signal of the magnetic field sensor 402 (i.e., the input signal to the detection circuit 420) changes abruptly (V → 0 → V''). Passing this abrupt change through a differentiation filter results in a pulse, allowing the magnetization reversal of the ferromagnetic-ferroelectric layer 402 to be detected by the pulse detection circuit. In another embodiment, the detection circuit 420 may include a differentiation circuit and a bit storage circuit that is provided downstream of the differentiation circuit and inverts its logic value each time the differentiation circuit outputs a pulse having an absolute value equal to or greater than a predetermined value. When the differentiation circuit outputs a pulse having an absolute value equal to or greater than the predetermined value, if the logic value held in the bit storage circuit is H(+1), the logic value held in the bit storage circuit changes to L(0), and if the logic value held in the bit storage circuit is L(0), the logic value held in the bit storage circuit changes to H(+1). Such a bit storage circuit may be configured using, for example, a flip-flop circuit or a latch circuit. If necessary, a circuit may be further provided that inputs a predetermined pulse having a logic value of H or L to the bit storage circuit each time the differentiation circuit outputs a pulse having an absolute value equal to or greater than the predetermined value. A circuit having such a function may be configured to include, for example, a pulse generating circuit capable of outputting a pulse of a predetermined logic value (H or L), and a trigger circuit that monitors the output of the differentiating circuit and causes the pulse generating circuit to generate a pulse of the predetermined logic value when it detects that the absolute value of the output of the differentiating circuit exceeds a predetermined value. The detection circuit 420 further including such a bit memory circuit can hold the output logic value of the detection circuit 420 until the direction of the external magnetic field is next reversed and the magnetizations of the soft magnetic layer 3 and the ferromagnetic-ferroelectric layer 402 are reversed.For example, if the held logic value in the state of Fig. 6(A) is H(+1), the held logic value in the state of Fig. 6(C) can be L(0). Conversely, if the held logic value in the state of Fig. 6(A) is L(0), the held logic value in the state of Fig. 6(C) can be H(+1).

[0061] The above description of the present invention has been given of magnetic field sensors 10, 210, 310, 410 and magnetic field detection devices 100, 200, 300, 400 in which the first electrode layer 1 and the ferromagnetic-ferroelectric layer 2 / 402 are in direct physical contact. However, the present invention is not limited to these configurations. For example, magnetic field sensors and magnetic field detection devices may further include one or more other layers between the first electrode layer and the ferromagnetic-ferroelectric layer. The other layers between the first electrode layer and the ferromagnetic-ferroelectric layer may be conductive or electrically insulating (dielectric), but are preferably paramagnetic or diamagnetic. Furthermore, when one or more electrically insulating layers are included between the first electrode layer and the ferromagnetic-ferroelectric layer, the total thickness of the other layers between the first electrode layer and the ferromagnetic-ferroelectric layer is preferably thin (i.e., the distance between the first electrode layer 1 and the ferromagnetic-ferroelectric layer is short), and may be, for example, 30 nm or less, or 10 nm or less.

[0062] The above description of the present invention has been given with reference to magnetic field sensors 10, 210, 410 and magnetic field detection devices 100, 200, 400 in which the ferromagnetic-ferroelectric layer 2 / 402 and the soft magnetic layer 3 / 203 are in direct physical contact. However, the present invention is not limited to these configurations. For example, magnetic field sensors and magnetic field detection devices may further include one or more layers other than the second electrode layer between the ferromagnetic-ferroelectric layer and the soft magnetic layer. The other layer between the ferromagnetic-ferroelectric layer and the soft magnetic layer may be conductive or electrically insulating (dielectric), but is preferably a paramagnetic or diamagnetic layer. Furthermore, the total thickness of the other layers between the ferromagnetic-ferroelectric layer and the soft magnetic layer is preferably thin (i.e., the distance between the ferromagnetic-ferroelectric layer and the soft magnetic layer is short), and may be, for example, 10 nm or less, or 5 nm or less.

[0063] In the above description of the present invention, the magnetic field sensors 10, 410 and magnetic field detection devices 100, 400 are described as having a configuration in which the soft magnetic layer 3 and the second electrode layer 4 are in direct physical contact. However, the present invention is not limited to these configurations. For example, the magnetic field sensors and magnetic field detection devices may further include one or more other layers between the soft magnetic layer and the second electrode layer. The other layer between the soft magnetic layer and the second electrode layer may be conductive or electrically insulating, but is preferably a paramagnetic or diamagnetic layer. Furthermore, when an electrically insulating layer is included between the soft magnetic layer and the second electrode layer, the total thickness of the other layers between the soft magnetic layer and the second electrode layer is preferably thin (i.e., the distance between the soft magnetic layer and the second electrode layer is short), and may be, for example, 30 nm or less, or 10 nm or less. [Explanation of symbols]

[0064] 1: first electrode layer, 2, 402: ferromagnetic / ferroelectric layer, 3, 303: soft magnetic layer, 4, 304: second electrode layer, 10, 210, 310, 410: magnetic field sensor, 20, 420: detection circuit, 100, 200, 300, 400: magnetic field detection device, M1, M1', M1 ip , M2, M2', M2ip :Magnetization, P1, P2, P2', P2 ip : Electric polarization

Claims

1. a first electrode layer; a ferromagnetic / ferroelectric layer comprising a ferromagnetic / ferroelectric material having perpendicular magnetic anisotropy, in which electric polarization including a perpendicular component is induced by application of a perpendicular magnetic field; a soft magnetic layer comprising a soft magnetic material having perpendicular magnetic anisotropy; A laminated structure including the following in the above order, The laminated structure is a second electrode layer, the second electrode layer being disposed so that the ferromagnetic-ferroelectric layer is sandwiched between the second electrode layer and the first electrode layer; Including, When the soft magnetic layer is conductive, the soft magnetic layer may also serve as the second electrode layer, A magnetic field sensor, characterized in that the electric polarization induced in the ferromagnetic-ferroelectric layer is detected as an electric signal generated between the first electrode layer and the second electrode layer.

2. the laminated structure includes the second electrode layer separate from the soft magnetic layer, 2. The magnetic field sensor according to claim 1, wherein the laminated structure includes, in this order, the first electrode layer, the ferromagnetic-ferroelectric layer, the soft magnetic layer, and the second electrode layer.

3. the laminated structure includes the second electrode layer separate from the soft magnetic layer; 2. The magnetic field sensor according to claim 1, wherein the laminated structure comprises, in this order, the first electrode layer, the ferromagnetic-ferroelectric layer, the second electrode layer, and the soft magnetic layer.

4. The saturation magnetization of the soft magnetic layer at 25° C. is Ms １ (unit: emu / cm ３ ) and the thickness of the soft magnetic layer is t １ (unit: nm), and the coercive force of the ferromagnetic / ferroelectric layer at 25° C. is Hc ２ (unit: Oe), the ratio is 4πMs １ t １ / Hc ２ The magnetic field sensor according to any one of claims 1 to 3, wherein the value of is 1000 nm or more.

5. The coercive force of the soft magnetic layer at 25° C. is Hc １ (unit: Oe), and the residual magnetization of the ferromagnetic / ferroelectric layer at 25°C is Mr ２ (unit: emu / cm ３ ) and the thickness of the ferromagnetic / ferroelectric layer is t ２ (unit: nm), the ratio 4πMr ２ t ２ / Hc １ The magnetic field sensor according to any one of claims 1 to 3, wherein the value of is less than 3000 nm.

6. 4. The magnetic field sensor according to claim 1, wherein the ferromagnetic / ferroelectric layer contains a material represented by the following composition formula (2) and exhibits ferromagnetic / ferroelectric properties and perpendicular magnetic anisotropy: (Bi １－ａ X ａ ) １－ｂ M ｂ ) ３ …(22) (In composition formula (2), X represents one or more elements selected from Mg, Ca, Sr, Ba, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu; M represents one or more elements selected from Ti, V, Cr, Mn, Co, Ni, Cu, and Zn; and a and b represent real numbers satisfying 0≦a≦0.8 and 0≦b≦0.5, with the proviso that at least one of a and b is not 0.)

7. 4. The magnetic field sensor according to claim 1, wherein the soft magnetic conductive layer contains a soft magnetic material represented by the following composition formula (3): Co ｘ Ni １－ｘ Fe ２ O ４ …(3) (In the composition formula (1), x is a real number from 0 to 0.8.)

8. A magnetic field sensor according to any one of claims 1 to 3; a detection circuit electrically connected to the first electrode layer and the second electrode layer, for detecting the electric polarization induced in the ferromagnetic-ferroelectric layer as an electric signal; A magnetic field detection device comprising:

Images