Method of using irreversible circuit elements

Abstract

Non-reversible circuit elements are used in the 3GHz to 6GHz band. [Solution] A method for using an irreversible circuit element comprising a ferrimagnetic material having a main surface, a plurality of central conductors arranged on the main surface of the ferrimagnetic material in an insulated state from each other, and a laminated magnet in which a ferrite magnet containing Sr and a rare earth magnet containing Sm are stacked, wherein the laminated magnet is arranged opposite the plurality of central conductors, A method for using the non-reversible circuit element, wherein the frequency characteristics of the insertion loss in the non-reversible circuit element are such that, in a temperature range of -40°C to 125°C, the resonant frequency of the main band and the attenuation pole closest to the resonant frequency are separated by 200 MHz or more.

Description

Technical Field

[0001] This application relates to irreversible circuit elements.

Background Art

[0002] Irreversible circuit elements include isolators, circulators, etc., and are used in the transmission and reception circuits of devices such as mobile phones and their base stations. Irreversible circuit elements are used for the purpose of preventing damage to amplifiers and obtaining stable output power with high linearity, and have a function such that the insertion loss in the signal transmission direction is small and the transmission loss in the reverse direction is large. For example, Patent Document 1 discloses an irreversible circuit element that can be miniaturized.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] With the progress of information and communication technologies, it is required to transmit larger amounts of information, and the frequency of electromagnetic waves used in information and communication networks such as mobile phone communications also uses high-frequency bands capable of transmitting large amounts of information. Specifically, an irreversible circuit element corresponding to a frequency in the 3 GHz to 6 GHz band called the Sub-6 frequency band is required.

[0005] The present disclosure aims to provide an irreversible circuit element adapted to the 3 GHz to 6 GHz band.

Means for Solving the Problems

[0006] An irreversible circuit element according to one embodiment of the present disclosure comprises a ferrimagnetic material having a main surface, a plurality of central conductors arranged on the main surface of the ferrimagnetic material in an insulated state from each other, and a laminated magnet in which a ferrite magnet containing Sr and a rare earth magnet containing Sm are laminated, the laminated magnet being arranged opposite the plurality of central conductors, wherein the combined temperature coefficient of the residual magnetic flux density of the laminated magnet is -0.14% / °C or more and -0.06% / °C or less.

[0007] The ferrimagnetic material may have a saturation magnetic flux density of 40 mT or more and 80 mT or less, and the temperature coefficient of the saturation magnetic flux density may be -0.45% / °C or more and -0.25% / °C or less.

[0008] The ratio of the thickness of the rare earth magnet to the total thickness of the ferrite magnet and the rare earth magnet may be 1 / 4 or more and 3 / 4 or less.

[0009] In the stacked magnet described above, the ferrite magnet may be closer to the plurality of central conductors than the rare earth magnet.

[0010] The combined temperature coefficient of the residual magnetic flux density of the stacked magnet may be -0.12% / °C or higher and -0.08% / °C or lower.

[0011] In the frequency characteristics of the insertion loss of the non-reversible circuit element, the resonant frequency of the main band and the attenuation pole closest to the resonant frequency may be separated by 200 MHz or more in the temperature range of -40°C to 125°C. [Effects of the Invention]

[0012] According to embodiments of this disclosure, an irreversible circuit element suitable for the 3GHz to 6GHz band is provided. [Brief explanation of the drawing]

[0013] [Figure 1] Figure 1 is an exploded perspective view showing one form of the irreversible circuit element of this embodiment. [Figure 2]Figure 2 shows the magnetic field strength applied to the ferrimagnetic material of the laminated magnet in the temperature range from 5°C to 125°C. [Figure 3A] Figure 3A shows the frequency characteristics of the VSWR and insertion loss of the irreversible circuit element of Example 1. [Figure 3B] Figure 3B shows the frequency characteristics of the attenuation of the irreversible circuit element of Example 1. [Figure 4A] Figure 4A shows the frequency characteristics of the VSWR and insertion loss of the irreversible circuit element of Comparative Example 1. [Figure 4B] Figure 4B shows the frequency characteristics of the attenuation of the irreversible circuit element of Comparative Example 1. [Figure 5A] Figure 5A shows the frequency characteristics of the VSWR and insertion loss of the irreversible circuit element of Comparative Example 2. [Figure 5B] Figure 5B shows the frequency characteristics of the attenuation of the irreversible circuit element of Comparative Example 2. [Figure 6A] Figure 6A shows the frequency characteristics of the input-side VSWR and insertion loss of the irreversible circuit element of Example 2. [Figure 6B] Figure 6B shows the frequency characteristics of the output-side VSWR and isolation of the irreversible circuit element of Example 2. [Figure 7A] Figure 7A shows the frequency characteristics of the input-side VSWR and insertion loss of the irreversible circuit element of Comparative Example 3. [Figure 7B] Figure 7B shows the frequency characteristics of the output-side VSWR and isolation of the irreversible circuit element of Comparative Example 3.

Embodiments for Carrying Out the Invention

[0014] Figure 1 is an exploded perspective view of the irreversible circuit element 30 of the present embodiment. The irreversible circuit element 30 is adapted to frequencies in the band of, for example, 3 GHz to 6 GHz and is used in the transmission and reception circuits of mobile phones and base stations of mobile phones. The external dimensions of the irreversible circuit element 30 are, for example, approximately 5 mm in length, 5 mm in width, and 2.5 to 4 mm in height, and the irreversible circuit element 30 is a lumped-constant type irreversible circuit element.

[0015] The non-invertible circuit element 30 includes a ferrimagnetic material 3, a plurality of center conductors, and a laminated magnet 2.

[0016] The ferrimagnetic material 3 has, for example, a disk shape having a main surface 3a. For example, the diameter of the main surface 3a is about 1.5 mm or more and 2.5 mm or less. The ferrimagnetic material 3 preferably has a low saturation magnetic flux density of, for example, 40 mT or more and 80 mT or less, and also has a low ferromagnetic resonance half-width (ΔH < 2500 A / m). Also, the temperature coefficient (temperature dependence) of the saturation magnetic flux density is preferably about -0.45% / °C or more and -0.25% / °C or less. Further, it is preferably 40 mT or more and 70 mT or less in saturation magnetic flux density, and preferably has a low ferromagnetic resonance half-width of ΔH < 2000 A / m). The temperature coefficient (temperature dependence) of the saturation magnetic flux density is more preferably about -0.4% / °C or more and -0.3% / °C or less. The ferrimagnetic material 3 is made of a ferrimagnetic compound such as yttrium iron garnet (YIG), for example.

[0017] The plurality of center conductors are electrically insulated from each other and are arranged on the main surface 3a of the ferrimagnetic material 3 in a state of being overlapped so as to cross each other. In the present embodiment, the center conductors 4, 5, and 6 are arranged at an angle of 120°. The ferrimagnetic material 3 and the center conductors 4, 5, and 6 constitute an assembly 20.

[0018] The laminated magnet 2 includes a rare earth magnet 2A and a ferrite magnet 2B. The rare earth magnet 2A contains Sm. Also, the ferrite magnet contains Sr. The rare earth magnet 2A has a plate shape having a main surface 2An and a main surface 2As, with the N pole on the main surface 2An side and the S pole on the main surface 2As side. Similarly, the ferrite magnet 2B has a plate shape having a main surface 2Bn and a main surface 2Bs, with the N pole on the main surface 2Bn side and the S pole on the main surface 2Bs side.

[0019] As shown in Figure 1, the rare earth magnet 2A and the ferrite magnet 2B are stacked such that the main surface 2An of the rare earth magnet 2A faces the main surface 2Bs of the ferrite magnet 2B. It is sufficient that the rare earth magnet 2A and the ferrite magnet 2B are stacked in close proximity, and they may be bonded together with an adhesive or the like. The stacked magnets 2 are positioned relative to the assembly 20 such that the main surface 2Bn of the ferrite magnet 2B faces the central conductors 4, 5, and 6.

[0020] The magnetic fields formed by the rare-earth magnet 2A and the ferrite magnet 2B are in the same direction, and the stacked magnet 2 forms a unified magnetic field. The stacked magnet 2 applies a magnetic field perpendicular to the main surface 3a of the ferrimagnetic material of the assembly 20.

[0021] Rare earth magnet 2A specifically consists of SmCo5 (1-5 system) and Sm2Co 17 Examples include (2-17 series) Sm-Fe-N series magnets. Ferrite magnet 2B is a SrO·Fe2O3 series magnet. Table 1 shows the remanent magnetic flux density and temperature coefficient of the remanent magnetic flux density for rare earth magnet 2A and ferrite magnet 2B.

[0022] [Table 1]

[0023] The overall residual magnetic flux density of the stacked magnet 2 is preferably between approximately 0.55 T and 1.0 T. Furthermore, the temperature coefficient of the overall residual magnetic flux density of the stacked magnet 2 is preferably between -0.14% / °C and -0.06% / °C, and more preferably between -0.12% / °C and -0.08% / °C. Hereinafter, the temperature dependence of the overall residual magnetic flux density of the stacked magnet 2 will be referred to as the combined temperature coefficient.

[0024] The value of the residual magnetic flux density (T) and the combined temperature coefficient (% / °C) of the stacked magnet 2 can be adjusted by changing the materials of the rare earth magnet 2A and the ferrite magnet 2B, and the ratio of the thicknesses of each magnet. For example, if the thickness of the rare earth magnet 2A is Tr and the thickness of the ferrite magnet 2B is Tf, the above-mentioned combined temperature coefficient can be achieved by adjusting the ratio of the thickness of the rare earth magnet 2A (Tr) to the total thickness of the rare earth magnet 2A and the ferrite magnet 2B (Tr+Tf) between 1 / 4 and 3 / 4.

[0025] More specifically, the above-mentioned composite temperature coefficient can be achieved by constructing the laminated magnet 2 with the thickness ratios shown in Table 2. In Table 2, as the rare earth magnet 2A, Sm2Co has a temperature coefficient of -0.04 to -0.02% / ℃. 17 Using this method, SrO·Fe2O3 with a temperature coefficient of -0.20 to -0.18% / ℃ was used as the ferrite magnet 2B. The external dimensions of the stacked magnet 2 are, for example, approximately 3 to 5 mm in length, 3 to 5 mm in width, and 0.8 to 1.2 mm in height when the operating bandwidth is 3.6 GHz to 4.0 GHz, and approximately 3 to 5 mm in length, 3 to 5 mm in width, and 0.8 to 2.2 mm in height when the operating bandwidth is 4.8 GHz to 5.0 GHz.

[0026] [Table 2]

[0027] Figure 2 shows the magnetic field strength applied to a ferrimagnetic material by the stacked magnet 2 in the temperature range of 5°C to 125°C. From the experimental results, the combined temperature coefficient of the remanent magnetic flux density Br by this stacked magnet has a strong correlation with the temperature change rate of the applied magnetic field strength. Therefore, in Figure 2, the combined temperature coefficient of the remanent magnetic flux density Br is converted and displayed as the temperature change rate of the applied magnetic field strength to the ferrimagnetic material.

[0028] For example, as a rare earth magnet 2A, Sm2Co 17Using this method, when SrO·Fe2O3 is used as the ferrite magnet 2B, the temperature dependence of the remanent magnetic flux density that can be achieved by adjusting the thickness is shown as described above. Thus, the stacked magnet 2 can achieve a remanent magnetic flux density value (0.55T or higher) that cannot be obtained with the ferrite magnet SrO·Fe2O3 alone, and the rare earth magnet Sm2Co 17 It possesses a combined temperature coefficient of remanent magnetic flux density (-0.14% / °C or higher, -0.06% / °C or lower) that cannot be obtained with a single element.

[0029] The irreversible circuit element 30 further comprises capacitive elements 8, 9, and 10 such as flat plate capacitors, a resistive element 11, and a resin case 7. The resin case 7 has a recess 13a, in which the assembly 20 is placed. The capacitive elements 8, 9, and 10 and the resistive element 11 are placed in recesses 13b, 13c, and 13d provided in the resin case 7, with one end electrically connected to one of the central conductors 4, 5, or 6 and an external terminal provided in the resin case 7, and the other end grounded to the bottom surface of the recess 13a provided in the resin case 7. The irreversible circuit element 30 further comprises an upper case 1 and a lower case 12, which are positioned above and below the resin case 7, thereby covering the resin case 7.

[0030] Next, the magnetic properties of the stacked magnet 2 of the irreversible circuit element 30 will be described with reference to Figure 2 and Table 3.

[0031] [Table 3]

[0032] As shown in Table 3, conventional irreversible circuit elements with an operating bandwidth of 700 MHz to 2.6 GHz have been designed so that the frequency characteristics of the non-reversible circuit elements, specifically the VSWR (voltage standing wave ratio), reverse loss, and insertion loss, do not fluctuate significantly within the operating temperature range of -40°C to 125°C, by roughly matching the temperature coefficient of the saturation magnetic flux density of the ferrimagnetic material with the combined temperature coefficient of the residual magnetic flux density of the magnet.

[0033] The inventors of this application conducted a detailed study on the design of irreversible circuit elements used in the 3-6 GHz band. As a result, they found that in such high-frequency bands, the absorption characteristics due to magnetic resonance generated when a DC magnetic field from a magnet is applied to a ferrimagnetic material are more sensitive to magnetic field strength than the resonance peak of the main band characteristics of an LC resonant circuit formed by a central conductor and a capacitive element. Therefore, they found that when the applied magnetic field decreases under high-temperature conditions, the attenuation pole of magnetic resonance shifts significantly to the lower frequency side, and the attenuation pole overlaps with the main band, which degrades the insertion loss in the transmission direction and worsens the linearity of the power amplifier output, making it difficult to meet the IMD (intermodulation distortion) standard (e.g., -50 dBc max).

[0034] In the non-reversible circuit element according to the embodiment of the present invention, the temperature dependence of the resonance peak of the main band characteristics of the LC resonant circuit and the temperature dependence of the magnetic resonance attenuation pole are considered, and the design differs from that of conventional non-reversible circuit elements so that the magnetic resonance attenuation pole does not overlap with the main band of the LC resonant circuit in the temperature range of -40°C to 125°C. Specifically, the saturation magnetic flux density of the ferrimagnetic material 3 is set to 40mT to 80mT, which is smaller than the value used in conventional non-reversible circuit elements. In addition, the temperature coefficient of the saturation magnetic flux density of the ferrimagnetic material 3 is set to -0.4% / °C to -0.3% / °C, which is smaller than conventional values. On the other hand, by using the multilayer magnet 2, the combined temperature coefficient of the residual magnetic flux density is set to the same value as that of a single Sm2Co 17 The temperature coefficient is set to between -0.14% / °C and -0.06% / °C, which is difficult to achieve with magnets. In other words, the combined temperature coefficient of the residual magnetic flux density of the laminated magnet 2 has a slope of 1 / 2 or less compared to the temperature coefficient of the saturation magnetic flux density of the ferrimagnetic material 3. As a result, as explained in the experimental results below, in the frequency characteristics of the insertion loss of the irreversible circuit element 30, it is possible to separate the resonant frequency of the main band and the attenuation pole closest to the resonant frequency by more than 200 MHz in the temperature range of -40°C to 125°C. Furthermore, the irreversible circuit element 30 can meet the required characteristics such as IMD.

[0035] Furthermore, Patent Document 1 discloses the realization of a low-profile irreversible circuit element by reducing the thickness of the permanent magnet of the irreversible circuit element. To reduce the thickness of the permanent magnet, it is stated that a rare-earth magnet with a higher residual magnetic flux density than a Sr ferrite magnet is used, and that the temperature characteristics of the residual magnetic flux density of a rare-earth magnet are flat, and that replacing the Sr ferrite magnet with a rare-earth magnet does not eliminate the temperature characteristics of the saturation magnetic flux density of a ferrimagnetic material. For this reason, Patent Document 1 discloses the use of a Sr ferrite magnet and an Nd-Fe-B magnet stacked together. Patent Document 1 discloses the use of two permanent magnets, but the temperature characteristics of the residual magnetic flux density obtained by the two permanent magnets must be similar to the temperature characteristics of the saturation magnetic flux density of a ferrimagnetic material.

[0036] In contrast, the non-reversible circuit element 30 of this embodiment has a temperature coefficient of saturation magnetic flux density of the ferrimagnetic material 3 that is smaller than that of the ferrimagnetic material of a conventional non-reversible circuit element, while the combined temperature coefficient of residual magnetic flux density of the laminated magnet 2 is larger than that of the residual magnetic flux density of the permanent magnet of a conventional non-reversible circuit element. In other words, the temperature coefficient of saturation magnetic flux density of the ferrimagnetic material 3 and the combined temperature coefficient of residual magnetic flux density of the laminated magnet 2 are set with a different approach than in the conventional method.

[0037] According to the non-reversible circuit element of this embodiment, by providing a laminated magnet in which a ferrite magnet containing Sr and a rare-earth magnet containing Sm are stacked, the combined temperature coefficient of the residual magnetic flux density can be set to -0.14% / °C or higher and -0.06% / °C or lower. Therefore, a non-reversible circuit element with excellent high-frequency characteristics and temperature characteristics in the 3-6 GHz band can be realized.

[0038] The following describes the results obtained by experimentation regarding the high-frequency characteristics and temperature characteristics of the non-reversible circuit element of this embodiment.

[0039] Figure 3A shows the frequency characteristics of VSWR and insertion loss for Example 1, a non-reversible circuit element of this embodiment, which has an operating bandwidth of 4.8 GHz to 5.0 GHz (4.9 GHz band). Figure 3B shows the frequency characteristics of attenuation with an expanded frequency range. The stacked magnet 2 is made of Sm2Co with a thickness ratio of 1:1. 17 A rare-earth magnet 2A made of [unspecified material] and a ferrite magnet 2B made of SrO·Fe2O3 were used. The remanent magnetic flux density was 0.7 to 0.8 T, and the temperature coefficient of the remanent magnetic flux density was between -0.12% / °C and -0.08% / °C.

[0040] Figures 3A and 3B show superimposed frequency characteristics obtained at temperatures of -40, 25, 85, 105, 115, and 125°C. The frequency characteristics shift as the temperature rises or falls. However, as shown in Figure 3A, the VSWR and insertion loss remain sufficiently low in the range from -40°C to 125°C, indicating that good frequency characteristics are obtained. Furthermore, as shown in Figure 3B, as the operating temperature rises, the magnetic resonance attenuation pole A shifts closer to the mainband resonance peak P. However, even at 125°C, the mainband resonance peak P and the magnetic resonance attenuation pole A are more than 200 MHz apart, so the impact on the mainband resonance characteristics is small.

[0041] Figure 4A shows the irreversible circuit element of Example 1, in which the multilayer magnet 2 is replaced with Sm2Co 17 The frequency characteristics of VSWR and insertion loss of Comparative Example 1, a non-reversible circuit element using a rare-earth magnet composed of Sm2Co, are shown. Figure 4B shows the frequency characteristics of attenuation over an expanded frequency range. 17 The remanent magnetic flux density of rare earth magnets composed of these materials is 0.9 to 1.2 T, and the temperature coefficient of the remanent magnetic flux density is -0.04 to -0.02% / °C.

[0042] As shown in Figure 4A, VSWR and insertion loss increase at the lower end of the operating band as the operating temperature rises. On the other hand, as shown in Figure 4B, even if the operating temperature rises or falls, the magnetic resonance attenuation pole A remains more than 500 MHz away from the resonance peak P of the main band. Therefore, in Comparative Example 1, although the magnetic resonance attenuation pole A can be controlled well, it can be seen that at high temperatures, VSWR and insertion loss worsen, especially at the lower end of the operating band.

[0043] Figure 5A shows the frequency characteristics of VSWR and insertion loss for Comparative Example 2, which is a non-reversible circuit element of Example 1 that uses a ferrite magnet made of SrO·Fe2O3 instead of the multilayer magnet 2. Figure 5B shows the frequency characteristics of attenuation with an expanded frequency range. The residual magnetic flux density of the ferrite magnet made of SrO·Fe2O3 is 0.33 to 0.45 T, and the temperature coefficient of the residual magnetic flux density is -0.20 to -0.18% / °C.

[0044] As shown in Figure 5A, VSWR and insertion loss increase across the entire operating band as the operating temperature rises. Also, as shown in Figure 5B, as the operating temperature rises, the magnetic resonance attenuation pole A approaches the resonance peak P in the main band, and at 125°C, it is only about 150 MHz away from the resonance peak P. Therefore, in Comparative Example 2, it can be seen that as the temperature rises, VSWR and insertion loss worsen across the entire operating band, and the effect of the magnetic resonance attenuation pole A becomes apparent at the resonance peak P.

[0045] Figure 6A shows the frequency characteristics of the input-side VSWR and insertion loss of Example 2, which is a non-reversible circuit element of this embodiment with an operating bandwidth of 3.4 GHz to 3.8 GHz (3.6 GHz band). Figure 6B similarly shows the frequency characteristics of the output-side VSWR and isolation. The stacked magnet 2 is the same as in Example 1. As shown in Figures 6A and 6B, all characteristics of the input-side VSWR, output-side VSWR, insertion loss, and isolation maintain sufficiently good values ​​in the temperature range of -40°C to 125°C, indicating that good frequency characteristics can be obtained.

[0046] Figure 7A shows the frequency characteristics of the input-side VSWR and insertion loss for Comparative Example 3, which is an irreversible circuit element of Example 2 that uses a ferrite magnet made of SrO·Fe2O3 instead of the multilayer magnet 2. Figure 7B similarly shows the frequency characteristics of the output-side VSWR and isolation. Similar to Comparative Example 2, the residual magnetic flux density of the ferrite magnet made of SrO·Fe2O3 is 0.33 to 0.45 T, and the temperature coefficient of the residual magnetic flux density is -0.20 to -0.18% / °C. In Figures 7A and 7B, the frequency characteristics obtained at temperatures of -40, 25, 85, and 125°C are shown superimposed.

[0047] As shown in Figure 7A, the input VSWR or insertion loss increases across the entire operating bandwidth as the operating temperature rises or falls. Also, as shown in Figure 7B, the output VSWR increases across the entire operating bandwidth as the operating temperature rises or falls, and the isolation deteriorates. Therefore, it can be seen that in Comparative Example 3, the input VSWR, output VSWR, insertion loss, and isolation characteristics all deteriorate across the entire operating bandwidth as the temperature rises or falls.

[0048] When an irreversible circuit element according to the embodiment of this disclosure was fabricated, it was possible to achieve characteristics of insertion loss of 1 dB (typ.), isolation of 10 dB (typ.), and intermodulation distortion of -60 dBc or less (with 5 W x 2 wave input) in a product with a typical frequency range of 3.4 to 3.8 GHz band / bandwidth of 400 MHz, which is included in the 5G band n78.

[0049] Furthermore, as can be seen from the above experiment, even when fabricating irreversible circuit elements used in frequency bands other than the 3.4-3.8 GHz band, such as 3 GHz to 6 GHz, the configuration of this embodiment is a very effective technique that exhibits little change in characteristics from low to high temperatures, and achieves low insertion loss, low IMD, and high isolation. [Industrial applicability]

[0050] The irreversible circuit elements of this disclosure can be used in various bandwidths, and are particularly suitable for use in the 3 to 6 GHz bandwidth. [Explanation of Symbols]

[0051] 1 Upper case 2 stacked magnets 2A rare earth magnet 2An, 2As, 2Bn, 2Bs, 3a main surface 2B Ferrite Magnet 3. Ferrimagnetic material 4, 5, 6 Center conductor 7. Resin case 8, 9, 10 Capacitive elements 12 Lower case 13a~13d Recess 20 assemblies 30 Non-reversible circuit elements

Claims

1. A ferrimagnetic material having a main surface, A plurality of central conductors are arranged on the main surface of the ferrimagnetic material in a manner that insulates them from each other, A laminated magnet comprising a ferrite magnet containing Sr and a rare earth magnet containing Sm, wherein the laminated magnet is arranged opposite to the plurality of central conductors, A method for using a non-reversible circuit element, comprising: In the aforementioned irreversible circuit element, the frequency characteristics of the insertion loss are such that, in a temperature range of -40°C to 125°C, the resonant frequency of the main band and the attenuation pole closest to the resonant frequency are separated by 200 MHz or more. Method of using irreversible circuit elements.

2. The method for using the non-reversible circuit element according to claim 1, wherein the combined temperature coefficient of the residual magnetic flux density of the stacked magnet is -0.14% / °C or more and -0.06% / °C or less, and the slope is 1 / 2 or less compared to the temperature coefficient of the saturation magnetic flux density of the ferrimagnetic material.

3. The temperature coefficient of the saturation magnetic flux density of the ferrimagnetic material is -0.45% / °C or higher and -0.25% / °C or lower. The saturation magnetic flux density of the ferrimagnetic material is 40 mT or more and 80 mT or less. A method for using the irreversible circuit element according to claim 1.

4. The combined temperature coefficient of the residual magnetic flux density of the stacked magnet is -0.12% / °C or higher and -0.08% / °C or lower. A method for using the irreversible circuit element according to claim 1.

5. The ferrimagnetic material has a ferromagnetic resonance half-width ΔH < 2500 A / m. A method for using the irreversible circuit element according to claim 1.

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