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 (1) β = [Hcj(T1)-Hcj(T2)]/Hcj(T1)/[T1-T2]×100 … Read MoreContinue Reading
Strongest Commercial Permanent Magnet
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 magnets (ferrite, NdFeB, SmCo and AlNiCo, etc.) were discovered and… Read MoreContinue Reading
Magnetize a Magnet and Demagnetize a Magnet
The basic way to magnetize a magnet 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 magnet rotate to the magnetization direction. When all the micro magnetic domains aligned along the same direction, the magnet is magnetized to the saturation state. Demagnetizing a magnet is the opposite process of magnetizing a magnet as described above. Just alternative the charging current… Read MoreContinue Reading
Do 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 the demagnetizing field is lower than a threshold value) or… Read MoreContinue Reading
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, resulting in the deterioration of magnetic properties… Read MoreContinue Reading
Sintered SmCo Magnet Grades
Samarium cobalt (SmCo) magnets include 1:5 type (SmCo5) and 2:17 type (Sm2Co17) magnets. Both types of SmCo magnet grades basically include three parts, i.e. “letter 1” + “number” + “letter 2”. The three parts in sintered SmCo magnet grades present material type, (BH)max value (in CGS unit) and Hcj level, respectively. The part “letter 1” are “XG” and “XGS” for sintered SmCo5 and Sm2Co17 magnets, respectively. Besides, the Hcj levels of sintered SmCo5 magnets include “default” (Hcj ≥ 15 kOe)… Read MoreContinue Reading
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 REPMs. Compared with other types of permanent… Read MoreContinue Reading
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 the working temperature in various… Read MoreContinue Reading