How to Measure the Coercivity of Ferrite Magnets
I. Introduction
Ferrite magnets, as an important type of permanent magnet material, are widely used in various fields such as electronics, automotive, and industrial machinery due to their cost - effectiveness, good corrosion resistance, and relatively stable magnetic properties. Coercivity is a crucial parameter that characterizes the ability of a magnetic material to resist demagnetization. Accurately measuring the coercivity of ferrite magnets is essential for quality control, material research, and product design. This article will comprehensively introduce the methods for measuring the coercivity of ferrite magnets, including the principles, equipment, procedures, and factors affecting the measurement results.
II. Understanding Coercivity
A. Definition and Types
Coercivity is defined as the magnetic field strength required to reduce the magnetization of a magnetized material to zero after it has been saturated magnetized. There are two main types of coercivity: normal coercivity (HcB) and intrinsic coercivity (HcJ). Normal coercivity refers to the magnetic field strength needed to reduce the magnetic flux density (B) to zero, while intrinsic coercivity is related to the reduction of the intrinsic magnetization (J) to zero. For ferrite magnets, intrinsic coercivity is often of more concern as it better reflects the material's resistance to demagnetization at the atomic level.
B. Significance in Ferrite Magnets
The coercivity of ferrite magnets determines their magnetic stability and performance in practical applications. A higher coercivity means that the magnet can withstand stronger external demagnetizing fields without losing its magnetization significantly. This is crucial in applications such as electric motors, where the magnets are exposed to alternating magnetic fields. A low - coercivity ferrite magnet may be easily demagnetized, leading to a decrease in motor performance or even failure.
III. Measurement Principles
A. Magnetic Hysteresis Loop
The measurement of coercivity is based on the concept of the magnetic hysteresis loop. When a magnetic material is subjected to a changing magnetic field, its magnetization (M) or magnetic flux density (B) does not follow a linear relationship with the applied magnetic field strength (H). Instead, it forms a closed loop called the hysteresis loop. The coercivity is one of the key points on this loop. By measuring the magnetic field strength at which the magnetization or magnetic flux density returns to zero during the demagnetization process, we can determine the coercivity of the material.
B. Relationship between Magnetic Quantities
In a magnetic material, the magnetic flux density B is related to the intrinsic magnetization J and the applied magnetic field strength H by the equation B=μ0(H+J), where μ0 is the permeability of free space (μ0=4π×10−7 T⋅m/A). During the measurement of the hysteresis loop, we can measure either B−H or J−H relationships to obtain the coercivity values.
IV. Measurement Equipment
A. Vibrating Sample Magnetometer (VSM)
- Principle
A VSM operates on the principle of electromagnetic induction. When a vibrating magnetized sample is placed in a set of pickup coils, an alternating electromotive force (EMF) is induced in the coils. The magnitude of this EMF is proportional to the magnetic moment of the sample. By measuring the induced EMF and knowing the vibration parameters of the sample, the magnetic moment of the sample can be calculated. Then, by varying the applied magnetic field and measuring the corresponding magnetic moments, the magnetic hysteresis loop can be obtained, and the coercivity can be determined. - Components
A typical VSM consists of a sample vibration system, a pair of pickup coils, a magnetic field generation system (usually an electromagnet), a signal detection and amplification system, and a data acquisition and processing system. The sample vibration system can vibrate the sample linearly at a fixed frequency and amplitude. The pickup coils are used to detect the induced EMF generated by the vibrating sample. The magnetic field generation system provides a variable and uniform magnetic field for the sample. The signal detection and amplification system amplifies the weak induced EMF signals for further processing. The data acquisition and processing system records and analyzes the measured data to obtain the magnetic hysteresis loop and relevant magnetic parameters. - Advantages and Limitations
VSM has high sensitivity and can measure small magnetic moments accurately. It can measure a wide range of magnetic materials, including ferrite magnets, and can obtain both M−H and J−H hysteresis loops. However, VSM is relatively expensive, and the sample size is usually limited to small specimens due to the requirement of uniform vibration and magnetic field distribution.
B. SQUID Magnetometer
- Principle
A Superconducting Quantum Interference Device (SQUID) magnetometer is based on the Josephson effect and the quantum interference of superconducting currents. It can detect extremely weak magnetic fields with high precision. When a magnetized sample is placed near the SQUID sensor, the magnetic field generated by the sample causes a change in the superconducting current in the SQUID loop, which can be measured as a voltage change. By measuring this voltage change as a function of the applied magnetic field, the magnetic hysteresis loop of the sample can be obtained, and the coercivity can be determined. - Components
A SQUID magnetometer mainly includes a SQUID sensor, a superconducting magnet for generating the applied magnetic field, a cryogenic system to maintain the superconducting state (usually using liquid helium or a closed - cycle cryocooler), a signal detection and amplification system, and a data acquisition and processing system. The SQUID sensor is the core component, which is extremely sensitive to magnetic fields. The superconducting magnet provides a strong and stable magnetic field for the sample measurement. The cryogenic system is necessary to keep the SQUID sensor and some parts of the magnet in the superconducting state. The signal detection and amplification system converts the weak voltage signals from the SQUID sensor into measurable signals, and the data acquisition and processing system records and analyzes the data. - Advantages and Limitations
SQUID magnetometers offer the highest sensitivity among all magnetic measurement techniques, capable of detecting magnetic fields as weak as 10−15 T. They can measure very small samples and provide accurate magnetic property data. However, SQUID magnetometers are very expensive, and the operation requires a complex cryogenic environment, which makes them less accessible for routine measurements in some laboratories and industries.
C. Permeameter
- **Principle
A permeameter is designed to measure the magnetic properties of magnetic materials by directly measuring the magnetic flux and magnetic field strength. For coercivity measurement, it usually uses the principle of the magnetic circuit. The sample is placed in a magnetic circuit, and an electromagnet is used to apply a variable magnetic field. The magnetic flux through the sample is measured using a fluxmeter, and the magnetic field strength at the sample position is measured using a Hall probe or a search coil. By changing the current in the electromagnet and recording the corresponding magnetic flux and magnetic field strength values, the B−H hysteresis loop can be plotted, and the coercivity can be determined. - Components
A basic permeameter consists of an electromagnet, a sample holder, a fluxmeter, a magnetic field measurement device (such as a Hall probe), and a power supply for the electromagnet. The electromagnet provides the variable magnetic field for the sample. The sample holder is used to position the sample accurately in the magnetic circuit. The fluxmeter measures the magnetic flux through the sample, and the magnetic field measurement device measures the magnetic field strength at the sample location. The power supply controls the current in the electromagnet to vary the magnetic field. - Advantages and Limitations
Permeameters are relatively simple and cost - effective compared to VSM and SQUID magnetometers. They can measure relatively large samples, which is suitable for some industrial applications. However, their measurement accuracy is generally lower than that of VSM and SQUID magnetometers, especially for samples with complex shapes or non - uniform magnetization distributions.
V. Measurement Procedures
A. Sample Preparation
- Shape and Size Selection
The shape and size of the sample can affect the measurement results. For VSM and SQUID magnetometers, small and regular - shaped samples (such as cubes, cylinders, or thin films) are preferred to ensure a uniform magnetic field distribution and accurate vibration (in the case of VSM). For permeameters, the sample size should be appropriate for the magnetic circuit design to minimize edge effects and ensure accurate magnetic flux and field measurements. - **Surface Treatment
The surface of the sample should be clean and free of contaminants, as surface impurities can affect the magnetic properties and measurement accuracy. If necessary, the sample surface can be polished or cleaned using appropriate solvents. - **Initial Magnetization
Before measuring the coercivity, the sample should be saturated magnetized. This can be done by placing the sample in a strong magnetic field (usually much higher than the expected coercivity) for a sufficient time to ensure that all the magnetic domains are aligned in the same direction.
B. Equipment Calibration
- **VSM Calibration
Calibrate the VSM by measuring a standard sample with known magnetic properties. Adjust the parameters of the instrument, such as the vibration amplitude and frequency, the gain of the signal detection and amplification system, to ensure accurate measurement of the magnetic moment. Verify the linearity of the instrument by measuring samples with different magnetic moments within the expected measurement range. - **SQUID Magnetometer Calibration
For a SQUID magnetometer, calibrate the SQUID sensor by applying known magnetic fields and measuring the corresponding voltage outputs. Check the stability of the cryogenic system and the performance of the superconducting magnet. Ensure that the SQUID magnetometer is operating in its optimal range and that the background magnetic field is minimized. - **Permeameter Calibration
Calibrate the permeameter by measuring a standard magnetic sample with known B−H characteristics. Adjust the zero - point of the fluxmeter and the magnetic field measurement device. Check the linearity of the electromagnet's magnetic field generation by measuring the magnetic field strength at different currents.
C. Coercivity Measurement
- Using VSM
Place the saturated - magnetized sample in the VSM sample holder and start the vibration system. Gradually vary the applied magnetic field from the saturation value in the opposite direction (demagnetization process). Record the magnetic moment of the sample as a function of the applied magnetic field strength. Continue to decrease the magnetic field until it reaches a negative saturation value and then increase it back to the positive saturation value to complete the hysteresis loop measurement. Analyze the measured data to determine the coercivity values (HcB and HcJ if possible). - Using SQUID Magnetometer
Position the saturated - magnetized sample near the SQUID sensor in the cryogenic environment. Slowly change the applied magnetic field generated by the superconducting magnet in the demagnetization direction. Measure the voltage output of the SQUID sensor as a function of the applied magnetic field. Plot the magnetic hysteresis loop based on the measured data and determine the coercivity. - Using Permeameter
Place the saturated - magnetized sample in the sample holder of the permeameter. Apply a variable magnetic field using the electromagnet, starting from the saturation value and gradually decreasing it in the opposite direction. Measure the magnetic flux through the sample using the fluxmeter and the magnetic field strength at the sample position using the Hall probe or search coil simultaneously. Record the data and plot the B−H hysteresis loop. Determine the normal coercivity (HcB) from the loop.
VI. Factors Affecting Measurement Results
A. Temperature
Temperature has a significant impact on the magnetic properties of ferrite magnets. As the temperature increases, the thermal agitation of the magnetic moments increases, which can reduce the coercivity. Therefore, it is important to measure the coercivity at a specified temperature, usually room temperature, unless the application requires measurement at a different temperature. If measurements are made at non - room temperatures, appropriate temperature control and calibration of the measurement equipment are necessary.
B. Sample Orientation
The orientation of the sample with respect to the applied magnetic field can affect the measurement results. For anisotropic ferrite magnets, the coercivity is different along different crystallographic directions. To obtain accurate coercivity values, the sample should be oriented correctly according to the measurement requirements. For isotropic ferrite magnets, the sample orientation has less impact, but it is still important to ensure a consistent orientation during repeated measurements.
C. Magnetic Field Uniformity
The uniformity of the applied magnetic field is crucial for accurate coercivity measurement. Non - uniform magnetic fields can cause uneven demagnetization of the sample, leading to inaccurate hysteresis loops and coercivity values. In VSM and SQUID magnetometers, the sample should be placed in the region of high magnetic field uniformity. In permeameters, the magnetic circuit design should ensure a uniform magnetic field distribution at the sample position.
D. Measurement Speed
The speed at which the applied magnetic field is varied during the hysteresis loop measurement can also affect the results. If the measurement speed is too fast, the magnetic domains in the sample may not have enough time to respond to the changing magnetic field, resulting in a distorted hysteresis loop. Therefore, it is important to choose an appropriate measurement speed, usually slow enough to allow the sample to reach a stable state at each magnetic field value.
VII. Conclusion
Measuring the coercivity of ferrite magnets is a complex but essential task for understanding and utilizing these magnetic materials. By selecting the appropriate measurement equipment, following the correct measurement procedures, and considering the factors that can affect the measurement results, accurate coercivity values can be obtained. VSM, SQUID magnetometers, and permeameters are the main equipment used for coercivity measurement, each with its own advantages and limitations. Sample preparation, equipment calibration, and proper measurement techniques are key steps in ensuring the accuracy and reliability of the measurement results. Understanding the factors that can affect the coercivity measurement, such as temperature, sample orientation, magnetic field uniformity, and measurement speed, allows for better control of the measurement process and more meaningful interpretation of the results. With accurate coercivity data, researchers and engineers can optimize the design and performance of ferrite - magnet - based products in various applications.
Global Ferrite Magnet Market Size: An In - depth Analysis
I. Current Market Size and Overview
As of 2025, the global ferrite magnet market has witnessed significant growth and transformation. The market size has reached a substantial level, with various research reports providing different but complementary perspectives.
A. Overall Market Value
According to different research institutions, the global ferrite magnet market size in 2025 is estimated in the range of billions of US dollars. For instance, one report suggests that the market size was valued at approximately USD 10.0 billion in 2025, with a projection to grow to USD 16.4 billion by 2032, exhibiting a compound annual growth rate (CAGR) of 7.3% during the forecast period. Another analysis indicates that the market size was around USD 8.32 billion in 2025, expected to reach USD 9.83 billion by 2032 at a CAGR of 2.39%. These differences in estimates can be attributed to variations in research methodologies, data sources, and the scope of the market definition. However, they all point to a growing market with a positive outlook.
B. Market Segmentation by Type
Ferrite magnets can be broadly classified into hard ferrite magnets (permanent ferrite magnets) and soft ferrite magnets. Hard ferrite magnets have a dominant market share, accounting for over 70% of the global ferrite magnet market. This is mainly due to their cost - advantage in traditional motor applications and their expanding use in emerging fields. In 2025, the demand for hard ferrite magnets is estimated to reach 2.1 million tons. Soft ferrite magnets, on the other hand, are finding new growth opportunities in high - frequency and low - loss electronic and power technologies, especially in applications such as new energy vehicles and data center power modules.
II. Regional Market Analysis
A. Asia - Pacific Region
The Asia - Pacific region is the largest market for ferrite magnets, accounting for a significant proportion of the global market share. In 2024, it dominated the market with a share of 74.77%. This region is home to major manufacturing hubs, especially in China, Japan, and South Korea. China, in particular, has a well - established ferrite magnet industry, with a large number of manufacturers and a comprehensive industrial chain. The country's large - scale production capacity and cost - effectiveness make it a major exporter of ferrite magnets globally. In 2025, the Chinese hard ferrite magnet market size reached 6.567 billion yuan, and the global hard ferrite magnet market size was 26.291 billion yuan.
B. North America
North America is another important market for ferrite magnets. The United States is the main market and supply participant in this region. International companies have set up research and development and regional distribution centers here, and local companies are also involved in the supply of mid - to high - end products. The market in North America is characterized by technological innovation and a focus on high - end applications. However, the introduction of heightened United States tariffs on imported ferrite magnets in early 2025 has significantly altered global trade flows and cost structures, affecting the market dynamics in this region.
C. Europe
Europe holds a certain market share in the global ferrite magnet market, with Germany and France being the main participating countries. Companies such as Murata and TDK have established research centers and regional service networks in Europe, mainly to meet the demand for high - end applications in the automotive electronics sector. The European market is currently in a stage of technological refinement and upgrading, with a supply system that mainly supports local high - end manufacturing industries.
D. Other Regions
The Middle East and Africa, and Latin America have relatively smaller market shares. In the Middle East and Africa, the supply mainly relies on the distribution networks of international companies, and some local companies are involved in the supply of basic models. The market in this region is in a stage of gradually expanding application scenarios, mainly serving the emerging electronic manufacturing needs in the region. In Latin America, countries such as Brazil are the main markets, and the supply depends on the regional distribution channels of international companies. The market is in a stage of cultivation and initial penetration of applications, mainly配套 (supporting) local consumer electronics and other basic fields.
III. Market Drivers
A. Growing Electronics Sector
The continuous growth of the electronics industry is a major driving force for the ferrite magnet market. With the increasing miniaturization and integration of electronic components, ferrite magnets are widely used in various electronic devices such as smartphones, tablets, and laptops. For example, in smartphones, ferrite magnets are used in speakers, vibrators, and wireless charging modules. The high - frequency and low - loss characteristics of soft ferrite magnets make them suitable for 5G communication base stations, data center server power supplies, and other high - end electronic applications, further driving market demand.
B. Increasing Industrial Applications
Ferrite magnets have a wide range of applications in the industrial sector. In the automotive industry, they are used in micro - special motors, sensors, and electric drive systems of new energy vehicles. The development of new energy vehicles and intelligent driving technology has led to an increasing integration of on - board electronic systems, which has raised the requirements for electromagnetic compatibility and created a broad market space for ferrite magnets. In addition, ferrite magnets are also used in electric tools, toys, and traditional industrial motors, providing stable demand for the market.
C. Technological Advancements
Technological innovation is constantly promoting the development of the ferrite magnet market. The research and development of high - performance and low - loss material formulas, as well as new preparation processes and intelligent manufacturing technologies, are improving the performance and quality of ferrite magnets. For example, the breakthrough in high - frequency low - loss soft magnetic material technology has enabled ferrite magnets to be applied in more high - end fields. At the same time, miniaturization packaging technology has made ferrite magnets more suitable for small - sized electronic devices.
IV. Market Challenges
A. Trade Policy Uncertainties
Global trade policies have a significant impact on the ferrite magnet market. The imposition of tariffs and trade barriers by some countries, such as the United States' tariffs on imported ferrite magnets, has disrupted the original global free - flow of goods. This has increased the landed costs of imported products, put pressure on downstream pricing, and forced original equipment manufacturers (OEMs) to re - evaluate their global procurement strategies. In addition, some countries' export controls on key magnetic materials for the purpose of safeguarding their domestic industrial chain security have also added uncertainties to the market supply.
B. Cost Pressures
The ferrite magnet industry is facing cost pressures from multiple aspects. The prices of raw materials such as iron oxide, strontium carbonate, and barium carbonate fluctuate, which directly affects the production costs of ferrite magnets. At the same time, with the increasing environmental protection requirements, companies need to invest more in environmental protection facilities and technologies to meet relevant regulations, which also increases production costs. In addition, labor costs in some manufacturing regions are also rising, further squeezing the profit margins of enterprises.
C. Performance Requirements
As the application fields of ferrite magnets continue to expand, the performance requirements are also constantly increasing. In high - end applications such as new energy vehicles and 5G communication, ferrite magnets need to have higher magnetic properties, better temperature stability, and lower losses. Meeting these high - performance requirements requires continuous research and development investment and technological innovation, which poses a challenge for some enterprises, especially small - and medium - sized enterprises with limited research and development capabilities.
V. Future Market Prospects
A. Market Growth Projections
Looking ahead to the period from 2025 to 2030, the global ferrite magnet market is expected to continue to grow. Market growth will rely more on technological innovation and value enhancement rather than simple capacity expansion. It is estimated that by 2030, the global market size will approach USD 14 billion. High - performance soft magnets and customized hard magnet products for specific fields will account for an increasing proportion of the market value, marking the industry's transition from "quantity - based growth" to "quality - based leap".
B. Emerging Application Areas
There are several potential emerging application areas for ferrite magnets. In the field of new energy, in addition to new energy vehicles, ferrite magnets can also be used in wind power generation and photovoltaic inverters. The high - reliability and cost - effectiveness of ferrite magnets make them suitable for these large - scale energy applications. In the medical field, ferrite magnets can be used in magnetic resonance imaging (MRI) equipment and other medical devices. With the continuous development of medical technology, the demand for high - performance ferrite magnets in this field is expected to increase. In addition, the Internet of Things (IoT) and artificial intelligence (AI) fields also offer new opportunities for ferrite magnets, as they are widely used in various sensors and intelligent devices.
C. Industry Trends
In the future, the ferrite magnet industry will present several trends. Firstly, the industry will further consolidate, and large - scale enterprises with strong research and development capabilities and brand advantages will gradually occupy a larger market share. Secondly, the supply chain will be more localized and regionalized. To cope with trade policy uncertainties and reduce supply chain risks, manufacturers will establish local production bases or deep - seated partnerships near major consumer markets. Thirdly, green and sustainable production will become an important development direction. Enterprises will need to adopt more environmentally friendly production processes and materials to meet the increasing environmental requirements of the market and society.
In conclusion, the global ferrite magnet market in 2025 is in a stage of active development, with a certain market size and a clear growth trend. Although it faces some challenges such as trade policy uncertainties, cost pressures, and performance requirements, the market prospects are still promising, driven by the growth of the electronics and industrial sectors, technological advancements, and the emergence of new application areas. Enterprises in the industry need to closely monitor market dynamics, strengthen technological innovation, and optimize their supply chain management to seize market opportunities and achieve sustainable development.
