The concept of remanence (Br)
Remanence is the magnetism remaining after removing it from a successful magnetization while no longer being under any external magnetic influence. Simply speaking, it’s what’s left of the magnetic force even after removal. Retentivity, residual induction, or remaining flux density are used as alternatives to remanence. Remanence is usually represented by the symbol Br while its units are in either Gauss(Gs) or Tesla(T). Gauss is the CGS unit of magnetic flux density. It is equivalent to 1 Maxwell per centimeter square. Tesla is the SI unit equivalent to 1 Weber per meter square. The corresponding value for these units is 10,000 Gs per 1 T. Furthermore. Tesla can also be derived by dividing 1 Newton(N) by a current in Amperes(A), then multiplying it in meters (m). (1 Tesla = 1 Newton(N)/Current(A) x Meter(m)). Both Gauss and Tesla are vector quantities; this means they measure in a three-dimensional unit system.
Values of remanence have a direct correlation with magnetic flux density. A direct correlation indicates that a higher remanence value indicates a higher amount of magnetic flux density. So, a neodymium magnet with 1000 Gs has more remanence than a neodymium magnet with 100 Gs. Neodymium magnets that have high remanence values are referred to as hard neodymium magnets. They are usually categorized when the inherent coercivity values exceed approximately 10 kiloAmpere per meter. Hard neodymium magnets do not easily magnetize or demagnetize. Because of this, they are usually used for and are suitable materials for making permanent neodymium magnets—alloys of neodymium, iron, and boron compromise this specific type of magnet. Permanent magnets, on the other hand, are types of magnets that create their magnetic field. Examples of permanent magnets are neodymium magnets. They have the highest magnetic properties in the category of permanent magnets. The high remanence of neodymium magnets makes it a go-to magnet for many technical, industrial, and commercial applications.
Consequently, magnets that have low remanence are soft. Their magnetic fields are reversible and can easily be magnetized and demagnetized. The main difference between permanent and temporary magnets is the generation and remanence. Permanent neodymium magnets can create their magnetic field and retain it. Meanwhile, temporary magnets can only attach to something when a magnetic field is externally emitted. Thus, a withdrawn magnetic field makes it lose its attachment. So, soft magnets are best used as temporary magnets. Electrical equipment like switching circuits and generators commonly utilize these types of magnets. An excellent example of a soft magnet is iron. Iron can easily be attracted and removed to the point that it can be dusted or flicked off from where it is magnetized.
A neodymium magnet’s remanence should be considered when canvassing for its uses. However, we should never forget that other factors like temperature and conditions may disrupt the magnetic field. While remanence is directly related to magnetic flux density, it is inversely related to temperature. This means that when temperature increases, remanence decreases. Another factor we should consider checking when checking for a neodymium magnet’s quality and remanence is erosion and oxidation. A humid area can induce oxidation and corrosion. These events can lessen and worsen the performance of a neodymium magnet.
Moreover, it’s essential to determine where the neodymium magnet should be used. If a neodymium magnet should be exposed heavily or consistently to collision, then temporary neodymium magnets might not be the best option. Applying these concepts in the industrial setting can affect many more factors and may even have a ripple effect wherein one factor affects another. Therefore, remanence measurement and determination should always be tied with their practical uses when looking for a neodymium magnet.
Today, hard and permanent neodymium magnets are more utilized. The growing consumer electronics and motors market has significantly demanded them, especially neodymium magnets. Although there is still a great demand for soft and temporary neodymium magnets, the gap between their demands widens as we continue moving forward on the path of innovation and technology.