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Soft Magnetic Materials

Your Professional Magnetic Components Manufacturer in China

Sunbow Group specializes in the design, development and production of new-type amorphous, nanocrystalline, silicon steel sheets and other magnetic materials and related products. The company's main products include various types of amorphous, nanocrystalline ribbons and high and low voltage current transformer cores, precision current transformer cores, common mode inductor cores, PFC inductor cores, high frequency power transformer cores and related devices.

Customized Solutions

We are at the forefront of a design led approach to delivering challenging and custom solutions for magnetic cores or components for production. Whether your need is simple or complex, we can develop a solution to achieve your goals. With in- house experts we can design, develop and test prototypes that meet performance and environmental requirements of your application.

Advanced Equipment

The company has advanced equipment such as large-scale vacuum smelting furnaces, pressure spraying belts, various magnetic annealing furnaces and close cooperation with domestic scientific research institutions and universities, which ensures the company's R & D ability and product quality.

Complete Qualifications

At present, the company has two production bases, with a number of patented technologies, and has passed ISO9001, IATF16949 quality management system certification. All products have passed ROHS, SGS and other environmental protection certifications.

Wide Range of Applications

The company mainly serves the fields of new energy vehicles, photovoltaic power generation, wind power generation, smart home appliances, smart meters, wireless charging, and various power supplies, inverters, filter inductors, and shielding materials in the national strategic emerging industries.

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Introduction of Soft Magnetic Materials

Soft magnetic materials are those materials that are easily magnetised and demagnetised. They typically have intrinsic coercivity less than 1000 Am-1. They are used primarily to enhance and/or channel the flux produced by an electric current. The main parameter, often used as a figure of merit for soft magnetic materials, is the relative permeability ( mr, where mr = B/moH), which is a measure of how readily the material responds to the applied magnetic field. The other main parameters of interest are the coercivity, the saturation magnetisation and the electrical conductivity.

Characteristics of Soft Magnetic Materials

High Permeability

Soft magnetic materials can be easily magnetized and demagnetized, allowing them to efficiently guide magnetic flux.

Low Coercivity

These materials require a small external magnetic field to reverse their magnetization, which makes them suitable for alternating current (AC) applications.

Low Residual Magnetism

Once the external magnetic field is removed, soft magnetic materials lose their magnetization quickly.

What’s the Difference Between Hard and Soft Magnetic Materials

These distinctions refer specifically to ferromagnetic and ferrimagnetic materials, not just hard and soft materials. There are super-soft, very-soft, soft, semi-hard, and hard magnetic material classifications based on the magnetic coercivity (HC) measured in ampere/meter (A/m) units or Oersteds (Oe).
HC measures the ability of a magnetic material to resist becoming demagnetized when exposed to an external magnetic field. Materials with high HC values are generally called “hard” and are suited for making permanent magnets or for use in magnetic recording media. Various soft magnetic materials are used for inductor and transformer cores, microwave devices, shielding, and recording heads. Often, all the variations on soft materials are lumped together as soft magnetic materials in contrast to hard materials. The detailed magnetic materials classifications are:
●Super soft – HC is below 10 A/m
●Very soft – HC from 10 to <100 A/m
●Soft – HC from 100 to <1000 A/m
●Semi-hard – HC from 1000 to <2000 A/m
●Hard – HC is 2000 A/m and greater
The difference between hard and soft magnetic materials is not quite that simple. Some materials, like metallic iron, can be either hard or soft, depending on various factors. In the case of iron, the crystal grain size is the critical factor. When the crystal grains have sub-micron dimensions, they are comparable in size to the magnetic domains, and the grain boundaries pin the domains. Domain wall pinning occurs at surfaces so that no more surface than is needed is created. Pinned domains require a stronger coercive magnetic field applied to realign the domains. When the iron is annealed, the size of the crystal grains increases and the magnetic domains can more easily realign when a magnetic field is applied. That decreases the coercive field, and the material becomes magnetically softer. Varying the crystal structure in materials like iron can result in various magnetic properties, from hard to soft.

Magnetic Properties of Soft Magnetic Materials

High Saturation Magnetic Flux Density (Bs) and High Saturation Magnetization (Ms)
The soft magnetic material has high saturation magnetic flux density (bs) and saturation magnetization (ms). In this way, it is easier to obtain high permeability (μ) and low coercive force (Hc), which can also increase the magnetic energy density.

High Stability
The soft magnetic materials have high stability. It requires the above-mentioned soft magnetic materials properties to be stable enough to against environmental factors such as temperature and vibration.

High Magnetic Permeability

One of the soft magnetic materials properties is that they have high magnetic permeability. Magnetic permeability (with symbol μ) is a measure of sensitivity to magnetic fields.

Low Coercivity(Hc)

The soft magnetic material is not only easy to be magnetized by the external magnetic field, but also easy to be demagnetized by the external magnetic field or other factors. Its magnetic loss is also low.

Low Magnetic Loss and Electrical Loss

The magnetic loss and electrical loss of soft magnetic materials is low. It requires low coercivity (Hc) and high resistivity.

Types of Soft Magnetic Materials

Soft Magnetic Composites
The thickness of soft magnetic materials plays an important role for reducing eddy current losses, thus the soft magnetic alloys should be made in the form of thin lamination for dynamic uses. If we break down the other two dimensions of the soft magnetic strip, i.e., we use the soft magnetic alloys in the form of powders, then the eddy current losses can be further reduced, and the components made by which can be used at much higher frequencies. To realize such a utilization, the alloy powders are first prepared (in most cases by atomization methods), the particles then should be coated with an insulation layer, after that, the powders are mixed with a tiny amount of lubricant and compressed at an intense pressure of 600-800 MPa to the final shape. Soft magnetic products made by such processes are called Soft Magnetic Composites (SMCs) or powder cores. Another merit of SMCs is that they can be made into various specially shaped cores which are hardly made by the traditional lamination stacking methods, which benefits for novel design of electromagnetic devices. The main drawback of SMCs is that their permeabilities are relatively low. Nowadays the most common SMCs are made by powders of Fe, Fe-Si, Fe-Si-Al, Fe-Ni, amorphous and nanocrystalline alloys, etc.

Soft Ferrites
All the soft magnetic materials mentioned above are metals, therefore, eddy current effect cannot be avoided. Soft ferrites are distinctive in that they are ionic compounds and have resistivity several orders of magnitude higher than that of the metallic soft magnetic materials. Therefore, for applications with frequency up to 1 MHz, soft ferrites are the best choices with respect to the energy losses. The main drawback for soft ferrites is that the BS is relatively low. Two kinds of the most common soft ferrites are Mn-Zn ferrites ((Mn, Zn)Fe2O4) and Ni-Zn ferrites ((Ni, Zn)Fe2O4). Mn-Zn ferrites are commonly used below 1 MHz, whereas Ni-Zn ferrites can be used at much higher frequencies, but the BS and permeability for the latter are lower.

Iron and Low Carbon Steels
Iron and low carbon steels may be the most common and cheapest soft magnetic materials. They have a quite high value of BS ~2.15 T, which is only inferior to the expensive Fe-Co alloys. But their resistivities are rather low, which limits their usage in dynamic applications. Iron and low carbon steels are usually used for static/low frequency applications, such as the core of electromagnet, relays, and some low power motors for which the materials cost is the major concern.

Iron-silicon Alloys
Addition of a few of silicon to iron will increase its resistivity notably, therefore, is very beneficial for inhibiting the eddy current loss. Despite of slightly decrease of saturation magnetization and Curie temperature, Fe-Si alloys are widely used in electric machines operating at from 50 Hz to several hundreds Hz. To further reduce the eddy current loss, Fe-Si alloys are often rolled to the form of thin strips. The thickness for the most common Fe-Si alloy is equal to or less than 0.35mm. Depending on the conditions of rolling and heat treatment, Fe-Si alloy can be classified as Grain-Oriented (GO) and Non-Oriented (NO). GO Fe-Si is used for transformers, whereas NO Fe-Si is used for electric motors.

Iron-nickel Alloys
Nickel can be added to iron to form uniform solid solutions in a broad composition range of 35 wt. % to 80 wt. % Ni. The alloys with composition near Fe20Ni80 were named as Permalloy (nowadays people tend to call all the iron-nickel alloy with nickel content higher than 35 wt. % as Permalloy). Minor content of other elements such as Mo, Cu, and Cr are usually added to improve the magnetic properties of Permalloy. Processed by delicate composition adjustment and heat treatment, Permalloy can be one of the softest magnetic material in the world, the permeability of which can be as high as 1 200 000. One of the drawbacks of Permalloys is their saturation magnetization, which is only of about 0.8 T, much lower than that of iron and Fe-Si alloys. With decrease of the nickel content, BS will increase firstly, reach its maxima of 1.6T at around nickel content of 48 wt. %, however, the permeability will not be as good as alloys with high nickel content. Iron-nickel alloy is the most versatile magnetic alloy, its magnetic properties can be tuned by adjusting composition, magnetic annealing, and mechanical rolling, etc. Iron-nickel alloy also presents very good formability, which can be rolled down to as thin as 20 microns. As a result, nickel-iron alloys can be found in wide applications such as magnetic field shielding, ground fault interrupter, magnetic sensors, recording head for magnetic tapes, power electronics, etc.

Iron-cobalt Alloys
Adding cobalt to iron will increase both the Curie temperature and the BS. For cobalt content in the range of 33 wt. % to 50 wt. %, the BS can be as high as 2.4T. Although not as soft as iron-nickel alloy, iron-cobalt alloys present the highest value of BS among all the other magnetic alloys. To increase the formability, 2 wt. % of vanadium is added to the Fe50Co50 alloy, so that it can be rolled down to as thin as 50 microns. Addition of vanadium can also increase the resistivity of iron-cobalt alloy. Due to the highest BS, iron-cobalt alloys are indispensable for applications where high power to weight ratio is demanding, such as motors and transformers used in spaceborne devices.

Amorphous and Nanocrystalline Alloys
Amorphous alloys, also frequently called metallic glasses, can be produced by rapid solidification. There is no long-range order for the atoms in amorphous alloys, therefore, the resistivity is usually high, and there is no magneto crystalline anisotropy. Furthermore, amorphous ribbons as thin as around 20 to 30 microns can be easily produced by planar flow casting. All these characters guarantee amorphous alloys to be excellent candidates for soft magnets. According to the compositions, most of the commercially available amorphous soft magnets can be classified as Fe-base, Co-base, and (Fe, Ni)-based. For these three types, the total content of Fe, Co, and Ni is about 75-90 wt.%, the remanent are metalloids and glass forming elements such as Si, B, P, C, and Zr, Nb, Mo, etc. Among these types, Fe-based has the highest BS of about 1.6 T and lowest cost. The iron loss of Fe-based amorphous alloy is only one third of that of Fe-Si steel. If the Fe-Si steel in the power transformers can be replaced by Fe-base amorphous alloy, a huge amount of electric power can be saved, but the materials cost for the latter is higher. Co-based amorphous alloys usually have BS lower than 0.8 T but much higher permeability and near zero value of magnetostriction, which is comparable with the softest permalloy, and can perform even better at higher frequencies due to its higher resistivity. (Fe, Ni)-based amorphous alloys present medium magnetic properties compared with the other two.

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Common Problem of Soft Magnetic Materials

Q: What are noncrystalline solids?

A: Non- crystalline solids are “amorphous solids”. Unlike crystalline solids, they do not have a definite geometrical shape. The atoms in solids pack closely together than in liquids and gases. However, in non-crystalline solids, particles have a little freedom to move since they are not arranged rigidly as in other solids. These solids form after sudden cooling of a liquid. The most common examples are plastic and glass.

Q: What is non-crystalline material?

A: In condensed matter physics and materials science, an amorphous solid (or non-crystalline solid) is a solid that lacks the long-range order that is characteristic of a crystal. The terms "glass" and "glassy solid" are sometimes used synonymously with amorphous solid; however, these terms refer specifically to amorphous materials that undergo a glass transition.Examples of amorphous solids include glasses, metallic glasses, and certain types of plastics and polymers. Amorphous materials have an internal structure consisting of interconnected structural blocks that can be similar to the basic structural units found in the corresponding crystalline phase of the same compound. Unlike in crystalline materials, however, no long-range order exists. Amorphous materials therefore cannot be defined by a finite unit cell. Statistical methods, such as the atomic density function and radial distribution function, are more useful in describing the structure of amorphous solids.

Q: What are the characteristics of amorphous substances?

A: Amorphous solids have two characteristic properties. When cleaved or broken, they produce fragments with irregular, often curved surfaces; and they have poorly defined patterns when exposed to x-rays because their components are not arranged in a regular array. An amorphous, translucent solid is called a glass.

Q: How do you characterize amorphous materials?

A: Total diffraction analysis is one of the main characterization methods for determining the local structure within non-crystalline materials (amorphous solids). It makes use of the complete diffraction signal from a sample and treats each data point as an individual observation.

Q: What is the property of amorphous material?

A: Amorphous material is one kind of nonequilibrium material; its characteristic of atomic arrangement is more like liquid and has no long-range periodicity. The glass-forming ability of an alloy is closely related to its composition, and is quite different in various alloys.

Q: Do amorphous materials have defects?

A: As opposed to crystalline structures where various kinds of defects can be classified, coordination defects are the only main type of defects existent in amorphous structures. A coordination defect is defined as atom having a different coordination compared to the atoms of similar type in the structure.

Q: Why are amorphous materials brittle?

A: Amorphous solids display a ductile to brittle transition as the kinetic stability of the quiescent glass is increased, which leads to a material failure controlled by the sudden emergence of a macroscopic shear band in quasistatic protocols.

Q: How does amorphous affect properties?

A: Here are some of the common properties of amorphous polymers: They exhibit relatively low resistance to heat. Because they have a randomly ordered molecular structure that lacks a sharp melting point, they soften gradually as the temperature rises. They are not prone to shrinkage as they cool.

Q: What are the amorphous materials present?

A: Amorphous materials are those that have no detectable crystal structure. Amorphous film materials can be formed by: Deposition of a natural “glassy” material such as a glass composition. Deposition at low temperatures where the adatoms do not have enough mobility to form a crystalline structure (quenching).

Q: What is the difference between crystalline and non crystalline materials?

A: Crystalline solids are arranged in a regular pattern, whereas the amorphous solids do not show a regular arrangement. Due to this arrangement, the crystalline solids tend to possess the short-range order and long-range order, while the amorphous solids only possess a shorter range order.

Q: What are the properties of nanocrystalline materials?

A: Nanocrystalline materials exhibit increased strength/hardness, enhanced diffusivity, improved ductility/toughness, reduced density, reduced elastic modulus, higher electrical resistivity, increased specific heat, higher thermal expansion coefficient, lower thermal conductivity, and superior soft magnetic properties in comparison to conventional coarse-grained materials.

Q: What is the structure of a nanocrystalline material?

A: Nanocrystalline materials are single- or multiphase polycrystals with crystallite sizes in the range of a few nm (typically 5–20 nm), so that about 30 vol% of the material consists of grain or interphase boundaries. Due to the huge amount of grain boundaries and/or the broad distribution of interatomic spacings in the grain boundaries the properties of nanocrystalline materials differ from that of crystalline and amorphous materials with the same chemical composition. Nanocrystalline materials seem to permit the alloying of conventionally insoluble components.

Q: Why are nanocrystalline materials stronger?

A: The increase in yield strength is a result of enhanced fraction of grain boundary, which impedes the motion of dislocations. Hence the strength of the nanocrystalline metals has been shown to increase by as much as an order of magnitude as the grain size decreases to lower limits of the nanoscale.

Q: What are the applications of nanocrystalline materials?

A: Photovoltaic plants with energy storage systems. Solar-based hybrid energy systems with enriched overall efficiency. Hybrid energy systems and energy storage technologies. Phase change materials for thermal management. Organic dyes, quantum dot as sensitizers. Solid-state dye-sensitized solar cells.

Q: What are the properties of a nanocrystalline core?

A: The crystalline atomic structure of a nanocrystalline core creates superior magnetic properties, including high saturation and very high permeability across a wide frequency range. Nanocrystalline alloys also exhibit low AC loss and high efficiency, even at high temperatures.

Q: What is the thickness of nanocrystalline core?

A: Similar to the amorphous alloys, these materials are produced in a rapid quenching process with a subsequent heat treatment for formation of the nanocrystalline grains inside the material. Due to the production process, the material comes as a thin strip with a thickness of below 20 µm and variable width.

Q: What is the difference between amorphous and nanocrystalline cores?

A: By the end of the production process, the amorphous cores remain with a metallic-glass structure, while the nanocrystalline cores obtain a refined structure of nanometric magnetic grains scattered in an amorphous metallic matrix.

Q: What is the difference between nanocrystalline and polycrystalline?

A: There is a lot difference between Nanocrstalline and polycrystalline materials. In nanocrystalline materials, the grains are in nanosize, that is a few nanometers to around 100 nanometers. These is no exact distinction of this numbers. In a polycrtstalline material, the gran size has no limts.

Q: What is nanocrystalline technology?

A: Nanocrystals are carrier-free colloidal delivery systems that mean they are almost 100% drug. Drug delivered through nanocrystals have the potential of improving oral bioavailability of water insoluble drugs, reducing dose, increasing dissolution velocity and increasing particle stability.

Q: What is nanocrystalline phase?

A: Nanocrystalline materials (NCM) are single-phase or multiphase polycrystals, the crystal size of which is of the order of a few (typically 1–10) nanometers, so that about 50 vol. % of the material consists of grain or interphase boundaries.

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