What is Maximum Working Temperature of a Permanent Magnet?

What is Maximum Working Temperature of a Permanent Magnet? Permanent magnets are widely applied in various motors, sensors/instruments and electronics, their temperatures almost vary more or less during work. These temperature variations are resulted from eddy current effect and/or ambient temperature variation. Due to thermal fluctuation and magnetic domain evolution, a permanent magnet loses some or all magnetic flux when its temperature elevates. Here comes a question, how high temperature can a permanent magnet withstand to work? For a commercial… Read More

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What are Temperature Coefficients α and β of Permanent Magnets?

What are Temperature Coefficients (α and β) of Permanent Magnets? A permanent magnet’s magnetic properties change as a variation of temperature. For a permanent magnet, remanence (Br) and intrinsic coercivity (Hcj or Hci) are two major parameters, it is important to consider their changes with corresponding temperature variation at work. In order to describe the relative changes, they are calculated according to the following two formulas:             α = [Br(T1)-Br(T2)]/Br(T1)/[ T1-T2]×100         … Read More

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What is the Strongest Commercial Permanent Magnet in the World?

What is the Strongest Commercial Permanent Magnet in the World? Researchers and engineers have never stopped their steps to discover and develop novel permanent magnets since 1910s, and several types of permanent magnets had been commercialized and they have been widely used in motion, energy, electronics, medical and other high technologies in our daily life. However, little breakthrough has been taken in the past 18 years of the 21st century. In the current market, almost all types of commercial permanent… Read More

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How to Magnetize and Demagnetize a Permanent Magnet, respectively?

How to Magnetize and Demagnetize a Permanent Magnet, respectively? Due to random orientation for micro magnetic domains, a permanent magnet usually does not provide any magnetic flux when it is produced. It needs to be magnetized to saturation for use. So how to magnetize a permanent magnet? The basic principle is using a coil, i.e. an electromagnet, to generate a magnetic field. The generated magnetic field increases as the charging current increases, it drives micro magnetic domains of a permanent… Read More

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Do Permanent Magnets ever Lose Their Magnetism or Get Weaker?

Do Permanent Magnets ever Lose Their Magnetism or Get Weaker? Actually permanent magnets are not permanent. A Permanent Magnet is a material which has ability to resist demagnetization, including filed demagnetization and thermal demagnetization. The ability is characterized by a physical parameter called coercivity. In regard to field demagnetization, if a demagnetizing field or reverse field is smaller than a permanent magnet’s coercivity, the permanent magnet will keep the same magnetic flux (the demagnetizing process is linear and reversible when… Read More

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Corrosion Resistance of Rare Earth Permanent Magnets

Corrosion Resistance of Rare Earth Permanent Magnets In the Rare Earth Permanent Magnets family, the 1st generation 1:5 type SmCo magnets and 2nd generation 2:17 type SmCo magnets have high corrosion resistance due to the high cobalt content. Just like ferrite/ceramic magnets and AlNiCo magnets, SmCo magnets usually do not need any treatment for applications. The 3rd generation NdFeB magnets, however, are not the same. Although they have superior magnetic properties, they are more vulnerable to corrosion in humid environments,… Read More

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How to Understand the Grade of Sintered SmCo Magnet?

How to Understand the Grade of Sintered SmCo Magnet? Samarium cobalt (SmCo) magnets include 1:5 type (SmCo5) and 2:17 type (Sm2Co17) magnets. For both of sintered SmCo5 and Sm2Co17 magnets, their grades basically include three parts, i.e. “letter 1” + “number” + “letter 2”. Similar to sintered NdFeB magnets, the three parts in sintered SmCo magnets’ grades also present material type, (BH)max value (in CGS unit) and Hcj level, respectively. The difference is that the left part “letter 1” are… Read More

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What are Rare Earth Permanent Magnets (REPMs)?

What are Rare Earth Permanent Magnets (REPMs)? Rare earth permanent magnets (REPMs) are permanent magnets which are based on some rare earth elements (Sm, Nd, Pr, Dy, Ce, etc.) to form critical magnetic structures. In regard to crystal structures, REPMs include a. 1:5 type SmCo magnets (hexagonal CaCu5 type structure) also called 1st generation REPMs, b. 2:17 type SmCo magnets (rhombohedral Th2Zn17 type structure) also called 2nd generation REPMs and c. Nd2Fe14B magnets (tetragonal crystal structure) also called 3rd generation… Read More

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What is a Permanent Magnet?

What is a Permanent Magnet? A permanent magnet is a material that is able to provide magnetic flux when magnetized with an applied magnetic field. The ability is characterized by two key parameters: remanence and coercivity. Generally, a permanent magnet’s intrinsic coercivity (Hcj) is higher than 300kOe (in CGS unit) or 24kA/m (in SI unit). With higher coervivity, a permanent magnet has higher ability to resist demagnetization, including field demagnetization from the electric or magnetic circuit and thermal demagnetization from… Read More

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