JP2006213532A - Mn-Zn-Co-BASED FERRITE MATERIAL - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an Mn-Zn-Co-based ferrite material low in absolute value of iron loss while having less temperature change thereof and also high in absolute value of amplitude specific magnetic permeability while having less temperature change thereof in a wide temperature zone, particularly in a high-temperature region up to 140°C. <P>SOLUTION: The Mn-Zn-Co-based ferrite comprises, by mol, 52.0-53.0% Fe<SB>2</SB>O<SB>3</SB>, 0.15-0.5% CoO, 11.5-12.5% ZnO and the balance substantially MnO. The ferrite is characterized in that: an iron oxide having a chlorine content of ≤0.050 mass% is used as the above Fe<SB>2</SB>O<SB>3</SB>material; the obtained final sintered compact contains chlorine of ≤80 mass ppm; and the iron loss is low and the magnetic permeability is high in the wide range of temperature. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an Mn-Zn-Co based ferrite with low energy iron loss, and particularly suitable for use in a magnetic core such as a transformer for a switching power supply, which exhibits low iron loss and high magnetic permeability in a wide temperature range. -It relates to Co-based ferrite.

  Oxide magnetic materials are generally referred to as ferrite, and this ferrite is classified into hard magnetic materials such as Ba-based ferrite and Sr-based ferrite, and soft magnetic materials such as Mn-Zn-based ferrite and Ni-Zn-based ferrite. . A soft magnetic material is a material that is sufficiently magnetized even with a very small magnetic field, and is used in a wide range of fields such as power supplies, communication devices, measurement control devices, magnetic recording, and computers. Properties required for the soft magnetic material include a low coercivity, a high magnetic permeability, a high saturation magnetic flux density, and a low iron loss.

  As the soft magnetic material, in addition to the oxide ferrite, there are metal materials. Metallic soft magnetic materials are characterized by a higher saturation magnetic flux density than oxide-based materials, but they have low electrical resistance, and when used in a high frequency range, iron loss due to eddy currents increases. That's it. Therefore, in recent years when the frequency of use has been increased due to the demand for downsizing and high density of electronic devices, conventional metal materials should be used in the high frequency band of about 100 kHz used for switching power supplies. Has become almost impossible.

Against this background, Mn-Zn ferrite that generates less heat is mainly used as the magnetic core material for power transformers in the high frequency range. However, since this material also has an electrical resistivity value of several Ω · cm, by further increasing the electrical resistance and reducing eddy current loss, the overall iron loss is reduced and the heat generation is suppressed. Was desired. For this problem, for example, in Patent Document 1, a small amount of an oxide such as SiO ₂ or CaO is added as an accessory component to Mn—Zn ferrite and segregated at the grain boundary to increase the grain boundary resistance. A technique for suppressing heat generation by increasing the overall resistivity to several hundred Ω · cm or more is disclosed.

  Also, when used in a power transformer, consideration must be given to the temperature in the built-in equipment (operating temperature) and the temperature rise caused by the heat generated by the iron loss of the transformer material itself. For example, when the temperature at which the iron loss is minimized is near room temperature, the iron loss increases due to the rise in the temperature of the magnetic core due to heat generation, and the heat generation further increases accordingly, and this is repeated to accelerate the temperature increase. There is a risk of causing a so-called thermal runaway. The operating temperature of the transformer is usually around 50 to 70 ° C. To avoid this risk, the current material has a temperature at which the iron loss becomes a minimum of about 100 ° C. The material is designed such that the coefficient is negative and the iron loss decreases with increasing temperature. However, in the case of a material having a minimum iron loss temperature of about 100 ° C., if the temperature rises to 100 ° C. or higher, the iron loss also increases, so the risk of causing thermal runaway is extremely high.

  Furthermore, recently, in order to cope with the downsizing of electronic devices, the loading density of electronic components has been increased, and the temperature rise due to heat generation tends to be larger. For this reason, recent electronic components have been used in a high temperature range exceeding 100 ° C. or higher and 120 to 140 ° C., which has not been assumed so far. However, the design operating temperature is still around 100 ° C., and the demand for low iron loss in this temperature range remains unchanged. Therefore, the iron loss needs to be small in a wide temperature range, particularly in a high temperature range of about 100 ° C to 140 ° C.

  In addition, among the switching power supplies that use ferrite cores, the circuit type power supply called the forward type is ineffective because the excitation power consumed for exciting the transformer primary coil is not transmitted to the secondary side. It becomes electric power, and it becomes a factor of electric power efficiency fall. In order to reduce the excitation power, it is effective to increase the inductance of the transformer coil. For this purpose, it is necessary to increase the magnetic permeability of the core. For this reason, the ferrite core has a low iron loss over a wide temperature range, and at the same time, the permeability during the operation of the transformer over a wide temperature range, that is, the initial permeability for a small signal is not as large as about 200 mT. Improvement of the amplitude relative permeability under excitation is desired.

By the way, as a factor governing the iron loss, there is a magnetic anisotropy constant K ₁ , and the iron loss changes with the temperature change of the magnetic anisotropy constant K ₁ and is minimal at a temperature where K ₁ = 0. It becomes. Therefore, in order to improve the temperature change of the iron loss, it is necessary to reduce the temperature dependence of the magnetic anisotropy constant, that is, the absolute value of the iron loss temperature coefficient. The magnetic anisotropy constant is almost determined by the type of elements constituting the spinel compound, which is the main phase of ferrite. In the case of Mn-Zn ferrite, the temperature dependence is reduced by introducing Co ions. In addition, the absolute value of the iron loss temperature coefficient can be reduced (for example, see Non-Patent Documents 1 and 2). As a result, a material having a small iron loss in the vicinity of 100 ° C. and a relatively small iron loss in the temperature range before and after that can be obtained. However, by adding CoO, there is a problem that the iron loss minimum temperature decreases, or the iron loss temperature coefficient and the minimum temperature fluctuate greatly due to slight fluctuations in the firing temperature and the oxygen concentration of the firing atmosphere. ing.

For example, Patent Document 2 discloses that Mn—Zn—Co based ferrite containing Fe ₂ O ₃ , ZnO, and MnO as main components and containing less than 0.01 to 0.5 mol% of CoO has a K _{1 in a} wider temperature range than before. Therefore, it is disclosed that high magnetic permeability and low iron loss are realized in a wide temperature range. However, in the technique of Patent Document 2, as shown in FIG. 1 of the same document, the minimum temperature of the iron loss shifts to a considerably low temperature side, the iron loss value near the maximum operating temperature increases, and the temperature rises. The danger of accelerating is not resolved.

Further, Patent Document _{3, Fe 2 O 3, ZnO} , a main component MnO, in which further CaO in addition to CoO of 1000~4000ppm, Ta ₂ O _5, that the SiO ₂ added in combination, the number 100kHz In the above frequency range, it is possible to obtain a Mn-Zn ferrite with a low power iron loss in a wider temperature range than before, and with this amount of CoO added, the temperature characteristic curve of the power iron loss. Does not shift too much to the low temperature side. However, this technique also has a problem that depending on the main component composition, the temperature coefficient of iron loss and the minimum temperature greatly vary due to slight fluctuations in the firing temperature and the oxygen concentration in the atmosphere.

As a technique for improving these points, Patent Document 4 discloses a ferrite material having a low power loss and a small temperature change of the power loss. Further, this document discloses a ferrite material in which the temperature change of the power loss is small in a temperature range of 40 ° C. from 60 ° C. to 20 ° C. lower than the temperature at which the power loss is minimized. Patent Document 5 discloses a technique that not only obtains a small power loss by adding CoO and Nb ₂ O ₅ but also flattens the power loss to obtain a minimum power loss value in a wide temperature range. However, this technique does not sufficiently reduce the power loss, and it cannot be said that the temperature change of the power loss is sufficiently flattened. Moreover, in these documents, as a power transformer material, a low power loss is shown in a wider temperature range, particularly in a high temperature range of about 140 ° C., the temperature change is reduced, and the amplitude relative permeability is increased. There is no disclosure about what to do.

Furthermore, Patent Document 6 contains ZnO: 7.0 to 9.0 mol%, MnO: 36.8 to 39.2 mol%, and the balance iron oxide in a magnetic ferrite material mainly composed of iron oxide, zinc oxide and manganese oxide. Contains Co ₃ O ₄ as a component in the range of 2500 to 4500 ppm, the minimum value of power loss in the temperature range of 20-100 ° C. is 400 kW / m ³ or less, and the maximum and minimum values of power loss in that temperature range Magnetic ferrite materials with a difference of 150 kW / m ³ or less are disclosed. In the same document, the minimum value of power loss in the temperature range of 20-100 ° C. is 350 kW / m ³ or less, and the difference between the maximum value and the minimum value of power loss in the temperature range is 50 kW / m ³ or less. Ferrite materials are also disclosed. However, all of these have a minimum power loss of about 300 kW / m ³ , which does not fully meet the requirements for low loss, and low loss and high permeability at high temperatures up to 140 ° C. There is no disclosure of chemistry.

Patent Document 7 discloses that Co ₃ O ₄ : 2000 to Fe ₂ O ₃ : 53.2 to 54.5 mol%, ZnO: 7.5 to 11.5 mol%, and Mn-Zn ferrite containing the balance MnO as the main component. _{4500ppm, SiO 2: 60~140ppm, CaO} : a 300~700ppm, Nb ₂ O _5: 100~350ppm and ZrO _2: 50~450ppm or ZrO _2: in Mn-Zn ferrite containing the 50～450Ppm, power loss It is disclosed that the loss can be reduced and the loss can be reduced in a wide temperature range. However, as shown in Tables 1 and 2 of this document, there is no low loss of 250 kW / m ³ or less (100 kHz, 200 mT) at 100 ° C., even 25 to 140 ° C. There is no disclosure about obtaining a low loss of 350 kW / m ³ or less and a high amplitude relative permeability μa of 6500 or more from a low temperature to a high temperature range.
Japanese Patent Publication No. 36-002283 Japanese Patent Publication No. 04-033755 Japanese Patent Laid-Open No. 06-290925 Japanese Patent Laid-Open No. 08-191011 JP 09-134815 A JP 2001-080952 A JP 2002-231520 A "The effect of Cobalt substitutions on some properties of manganese zinc ferrites", ADGiles and FF Westendorp; J. Phys. D: Appl. Phys., 9 (1976) 2117 “Low-Loss Power Ferrites for Frequencies up to 500kHz”, TGWStijintjes and JJ Roelofsma; Adv.Cer.16 (1986) 493

  The present invention has been made in view of the situation as described above, and its purpose is that the absolute value of the iron loss and its temperature change are small in a wide temperature range, particularly in a high temperature range up to 140 ° C., and further the amplitude ratio. An object of the present invention is to provide an Mn-Zn-Co ferrite material having a high absolute value of magnetic permeability and a small temperature change.

We, in order to solve the prior art suffer the problem, Fe ₂ O _3, ZnO is a basic component, with the content of CoO is to investigate the effect on the temperature characteristic of the iron loss and magnetic permeability, Impurity content contained in the raw iron oxide, which has the largest weight ratio of raw materials among the basic components and has the greatest effect on properties, affects the iron loss and amplitude relative permeability in the final core and their temperature dependence. We have earnestly studied the influence. As a result, the effect of CoO differs depending on the composition range of the basic component. Therefore, by narrowing down the composition range of Fe ₂ O ₃ and ZnO and MnO and selecting the optimum CoO content according to the range, extremely low loss, It is possible to obtain a ferrite having a high relative permeability and a small temperature change up to a high temperature range. Furthermore, the amount of chlorine in the raw iron oxide is limited to a certain value or less, and the amount of chlorine in the final sintered body after firing It has been found that the effect is further improved by reducing the value to a predetermined value or less, and the present invention has been completed.

That is, the present invention is basic _{component, Fe 2 O 3: 52.0~53.0mol%} , CoO: 0.15~0.5mol%, ZnO: 11.5~12.5mol%, the balance being substantially MnO Mn-Zn-Co In the ferrite system, as the Fe ₂ O ₃ raw material, an iron oxide having a chlorine content of 0.050 mass% or less is used, and the final sintered body obtained is composed of a material containing chlorine of 80 massppm or less. It is Mn-Zn-Co based ferrite with low iron loss and high magnetic permeability in the temperature range.

  The iron oxide in the present invention is obtained by roasting an iron chloride solution.

The Mn—Zn—Co based ferrite of the present invention contains, as additive components, SiO ₂ : 50 to 500 massppm, CaO :: 200 to 2000 massppm, ZrO ₂ : 100 to 1500 massppm, and Ta ₂ O ₅ : 50 to 1000 massppm. It is characterized by that.

The Mn-Zn-Co ferrite of the present invention has a minimum iron loss temperature measured at a maximum magnetic flux density of 200 mT and a frequency of 100 kHz, and an iron loss at 100 ° C is 250 kW / m ³ or less, 25 to 140 ° C. The maximum value of the iron loss in the temperature range is 350 kW / m ³ or less.

Further, the Mn-Zn-Co ferrite of the present invention has an amplitude relative permeability μa measured at a maximum magnetic flux density of 200 mT and a frequency of 100 kHz of 6500 or more in a temperature range of 25 to 140 ° C., and the following formula (1) The coefficient of variation of μa defined by is characterized by being 1.5% or less.
Coefficient of variation (%) = (standard deviation of μa value in the temperature range of 25 to 140 ° C) / (average value of μa value in the temperature range of 25 to 140 ° C) x 100 (1)

  According to the present invention, it is possible to provide an Mn—Zn—Co based ferrite having a low iron loss and a high amplitude relative permeability in a wide temperature range of 25 to 140 ° C. The ferrite of the present invention is suitable for use in a transformer core material such as a switching power supply.

The basic components of the Mn-Zn-Co ferrite of the present invention are Fe ₂ O ₃ : 52.0 to 53.0 mol%, CoO: It has a composition of 0.15 to 0.5 mol%, ZnO: 11.5 to 12.5 mol%, and the balance MnO. The reason for limiting to the above range will be specifically described below.
Fe ₂ O ₃ : 52.0-53.0mol%
Fe ₂ O ₃ needs to be 52.0 mol% or more in order to make the iron loss minimum temperature 80 ° C. or more in relation to CoO. However, if it exceeds 53.0 mol%, the increase in iron loss near room temperature becomes rather large, so the upper limit is made 53.0 mol%. Preferably, it is the range of 52.3-52.7 mol%.

ZnO: 11.5-12.5mol%
As described above, the magnetic properties required for soft magnetic ferrite include high saturation magnetic flux density, high Curie temperature, low iron loss, and high magnetic permeability. Of these, the saturation magnetic flux density and the Curie temperature are almost determined by the ratio of the basic components MnO, ZnO, and Fe ₂ O ₃ . In a region where the amount of ZnO is small, the saturation magnetic flux density increases as the amount of ZnO increases, but at the same time, the Curie temperature decreases. If the amount of ZnO is less than 11.5 mol%, the effect of suppressing the temperature change of the magnetic permeability due to CoO is weak, and as a result, the iron loss value is high and the amplitude relative magnetic permeability is not improved. In addition, the temperature at which the iron loss is minimized is almost determined by the ratio of the basic components as described above. If the amount of ZnO is too large, the change in the iron loss minimum temperature with respect to fluctuations in the CoO content becomes very sensitive. The minimal temperature shifts greatly with a slight increase in CoO content. If the amount of ZnO is more than 12.5 mol%, the minimum iron loss temperature may change by about 25 ° C even if the amount of CoO is about 0.1 mol%. Therefore, in order to set the iron loss minimum temperature to 80 to 120 ° C., the ZnO content is set to a range of 11.5 to 12.5 mol%.

CoO: 0.15-0.5mol%
CoO has a function to reduce the temperature coefficient of permeability. However, if it exceeds 0.5 mol% and excessively contained, the temperature coefficient of iron loss becomes positive at room temperature or higher and thermal runaway occurs, and the change over time is large. It is not desirable. On the other hand, when the amount of CoO is less than 0.15 mol%, the effect of reducing the temperature change of the permeability is small. Therefore, the content of CoO is in the range of 0.15 to 0.5 mol%.
The ferrite of the present invention is Mn—Zn—Co—Fe ₂ O ₃ quaternary ferrite, and the remaining basic component other than the above Fe ₂ O ₃ , CoO, and ZnO is MnO.

As described above, it is most important to determine the composition range of the basic components Fe ₂ O ₃ , ZnO, MnO, and CoO. However, in order to stably realize a small iron loss and a large amplitude relative permeability at the same time, it is not sufficient, and it is necessary to limit the amount of impurities, particularly chlorine, in the raw iron oxide. . The influence of various impurities in the Mn-Zn ferrite is described, for example, on page 47 of the document "Ferrite" (Hiraga et al., Maruzen, 1986). In particular, there is no mention of effects on iron loss and permeability.

  In this regard, the inventors obtain a predetermined amplitude relative permeability by suppressing the unevenness of the structure such as the occurrence of abnormal grains and the variation in the grain size distribution of the grains and by improving the density of the sintered body core. At the same time, in order to reduce iron loss, it is necessary to regulate the chlorine content in the raw iron oxide to 0.050 mass% or less, and the amount of chlorine remaining in the final sintered body after firing is reduced to 80 massppm or less. I found that I needed to do it.

  The mechanism by which chlorine in the raw iron oxide affects the magnetic properties of the final sintered body has not yet been clearly elucidated, but in the manufacturing process of Mn-Zn-Co based ferrite, Since everything is mixed from iron oxide, it affects the crystal growth and crystal structure in the process involving chemical reaction such as calcination process and firing process after mixing raw materials, and the characteristics of the final sintered body, especially high This is thought to affect the iron loss and amplitude relative permeability on the temperature side. Therefore, it is necessary to reduce the amount of chlorine as much as possible before entering the reaction process as described above, that is, at the stage of the raw iron oxide. Further, if the amount of chlorine remaining in the final sintered body is large, it is considered that a large number of voids remain in the sintered body, resulting in a decrease in saturation magnetic flux density and relative permeability.

  In addition, as raw material iron oxide with a small amount of chlorine, iron oxide produced using an iron sulfide aqueous solution not containing chlorine is preferable. However, since such an aqueous solution increases the raw material cost, the iron chloride aqueous solution is roasted. It is preferable to use the obtained iron oxide, and in that case, iron oxide having an extremely small chlorine content can be obtained by performing heat treatment or washing with water after the roasting step.

In addition to the above basic components, the following additive components can be added to the ferrite of the present invention. That is, Fe ₂ O ₃ , ZnO, MnO, and CoO, which are the basic components of the ferrite of the present invention, form a spinel structure and do not form a spinel. SiO ₂ , CaO, Ta ₂ O ₅ , ZrO _By adding a small amount of additive components such as ₂ , Nb ₂ O ₅ and V ₂ O _5, it is possible to obtain a high-performance Mn—Zn—Co based ferrite material with less iron loss. In particular, the combined addition of SiO ₂ , CaO, Ta ₂ O ₅ and ZrO ₂ is effective, and the action is as follows.

SiO ₂ forms a grain boundary with CaO to increase the resistance of the grain boundary and contribute to the reduction of iron loss. However, if the addition amount is less than 50 massppm, the contribution is small, and if it exceeds 500 massppm, abnormal grain growth occurs during sintering, and the iron loss is greatly increased. When CaO coexists with SiO _2, it increases the grain boundary resistance and contributes to lower iron loss. However, when the amount added is less than 200 massppm, the effect is small, and when it exceeds 2000 massppm, the iron loss increases conversely. . Thus the added amount of SiO ₂ and CaO is SiO _2: 50~500massppm, CaO: preferably added in an amount of 200～2000Massppm.

Ta ₂ O ₅ effectively contributes to the increase in specific resistance in the presence of SiO ₂ and CaO. However, if the content is less than 50 massppm, the addition effect is poor. On the other hand, if it exceeds 1000 massppm, the iron loss is reversed. Increase. Therefore, Ta ₂ O ₅ is preferably added in the range of 50 to 1000 massppm. ZrO ₂ contributes to the reduction of iron loss at high frequencies by increasing the resistance of grain boundaries and coexisting with SiO ₂ , CaO and Ta ₂ O ₅ , as well as Ta ₂ O _5. However, if it is less than 100 massppm, the effect is poor. On the other hand, if it exceeds 1500 massppm, the effect of increasing the specific resistance is reduced and the iron loss is increased. Therefore, it is preferable to add ZrO ₂ in the range of 100 to 1500 massppm.

The iron oxide produced by roasting the iron chloride solution was heat-treated again in the temperature range up to about 500 ° C. or washed with water to obtain iron oxide containing various amounts of chlorine. The amount of chlorine in iron oxide was measured by fluorescent X-ray analysis. And after mixing raw materials so that it may have various compositions of Fe ₂ O ₃ , ZnO, and CoO as shown in Table 1 and Table 2 and the balance is MnO, calcination is performed at 930 ° C. for 3 hours. As shown in Tables 1 and 2, to this calcined powder, various amounts of SiO ₂ , CaO, Ta ₂ O ₅ and ZrO ₂ were added as additive components, and pulverized with a ball mill for 10 hours. It was molded into a ring shape with an outer diameter of 31 mm, an inner diameter of 19 mm, and a height of 7 mm. Thereafter, firing was performed at 1330 ° C. for 3 hours in a nitrogen / air mixed gas in which the oxygen partial pressure was controlled in the range of 1 to 5 vol%. At this time, the rate of temperature increase from 500 ° C. to 1300 ° C. was set to 650 ° C./hr.

The ring-shaped sample obtained as described above is wound with 5 turns on the primary side and 5 turns on the secondary side, and an AC BH loop tracer is used at a frequency of 100 kHz in a temperature range of 25 ° C to 140 ° C. The iron loss when excited to a magnetic flux density of 200 mT and the amplitude relative permeability μa in the temperature range of 25 to 140 ° C. were measured. Further, the coefficient of variation was obtained from the average value and the standard deviation of the amplitude relative permeability using the following (1). Furthermore, the amount of chlorine in the sintered body was measured by fluorescent X-ray analysis.
Coefficient of variation (%) = (standard deviation of μa value in the temperature range of 25 to 140 ° C) / (average value of μa value in the temperature range of 25 to 140 ° C) x 100 (1)

Based on the above measurement results, the temperature at which the iron loss is minimized, the iron loss value at 100 ° C, the maximum iron loss value in the temperature range of 25 to 140 ° C, and the amplitude relative permeability in the temperature range of 25 to 140 ° C. The minimum value and coefficient of variation are shown together in Tables 1 and 2. Here, Nos. 1 to 24 in Table 1 show inventive examples of the present invention, and Nos. 25 to 48 in Table 2 show comparative examples of the present invention. Furthermore, the temperature dependence of iron loss of No. 17 (invention example) in Table 1 and No. 39 (comparative example) in Table 2 is shown in FIG. 1, and the temperature dependence of amplitude relative permeability is shown in FIG. It was. As can be seen from Tables 1 and 2 and FIGS. 1 and 2, the examples of the present invention include the basic composition of Fe ₂ O ₃ , ZnO, MnO, and CoO and the composition of the additive components of SiO ₂ , CaO, Ta ₂ O ₅ , and ZrO _2. In addition to reducing the amount of chlorine in the raw iron oxide to 0.050 mass% or less and suppressing the amount of chlorine in the final sintered body to 80 massppm or less, the maximum magnetic flux density is obtained under any conditions. The iron loss minimum temperature measured at 200 mT and frequency 100 kW is in the range of 80 to 120 ° C, the iron loss at 100 ° C is 250 kW / m ³ or less, and the maximum iron loss in the temperature range of 25 to 140 ° C is 350 kW / m. ³ or less, and the amplitude relative permeability in the temperature range of 25 to 140 ° C is 6500 or more and the coefficient of variation is 1.5% or less. Low loss and high permeability over a wide temperature range, and the temperature change There are few Mn-Zn-Co ferrite materials.

  Since the ferrite of the present invention has high magnetic permeability over a wide temperature range, it can also be used for a noise filter core.

It is the graph which compared and showed the temperature dependence of the iron loss of the example of this invention and a comparative example. It is the graph which compared and showed the temperature dependence of the amplitude ratio magnetic permeability of the example of the present invention and the comparative example.

Claims (5)

In the Mn—Zn—Co based ferrite in which the basic components are Fe ₂ O ₃ : 52.0 to 53.0 mol%, CoO: 0.15 to 0.5 mol%, ZnO: 11.5 to 12.5 mol%, and the balance substantially consists of MnO, the Fe Low iron loss in a wide temperature range characterized by using iron oxide with a chlorine content of 0.050 mass% or less as the ₂ O ₃ raw material, and the final sintered body obtained is composed of chlorine containing 80 massppm or less And Mn-Zn-Co based ferrite showing high magnetic permeability. The Mn-Zn-Ni ferrite according to claim 1, wherein the iron oxide is obtained by roasting an iron chloride solution. As an additive _{component, SiO 2: 50~500massppm, CaO ::} 200~2000massppm, ZrO 2: 100~1500massppm and Ta ₂ O _5: according to claim 1 or 2, wherein the comprising the 50~1000massppm Mn-Zn-Co based ferrite. Iron loss minimum temperature measured at a maximum magnetic flux density of 200 mT, frequency of 100 kHz is 80 to 120 ° C, iron loss at 100 ° C is 250 kW / m ³ or less, and the maximum value of iron loss in the temperature range of 25 to 140 ° C is 350 kW / m ³ The Mn-Zn-Co-based ferrite according to any one of claims 1 to 3, wherein: The amplitude relative permeability μa measured at a maximum magnetic flux density of 200 mT and a frequency of 100 kHz is 6500 or more in the temperature range of 25 to 140 ° C., and the coefficient of variation of μa defined by the following formula (1) is 1.5% or less. The Mn-Zn-Co ferrite according to any one of claims 1 to 4.
Coefficient of variation (%) = (standard deviation of μa value in the temperature range of 25 to 140 ° C) / (average value of μa value in the temperature range of 25 to 140 ° C) x 100 (1)

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