What are the Properties of a Neodymium Magnet?
The main characteristic of neodymium magnets is how strong they are for their size. The magnetic field of a neodymium magnet occurs when a magnetic field is applied to it and the atomic dipoles align, which is the magnetic hysteresis loop. When the magnetic field is removed, part of the alignment remains in the magnetized neodymium.
The grades of neodymium magnets indicate their magnetic strength. The higher the grade number, the stronger is the magnet’s power. The numbers come from their properties expressed as mega gauss Oersteds or MGOe, which is the strongest point of its BH Curve.
The “N” grading scale begins at N30 and goes to N52, though N52 magnets are seldom used or only used in special cases. The “N” number may be followed by two letters, such as SH, which indicate the magnet’s coercivity (Hc). The higher the Hc, the higher the temperature the neo magnet can endure before it loses its output.
The chart below lists the most common grades of neodymium magnets presently being used.
The approximate maximum working temperature of each grade is indicated below. The XX is the maximum energy product in MGOe.
|Neodymium Grade||Max Temp|
|Nxx 12000 Oe||80 C/175 F|
|NxxM 14000 Oe||100 C/212 F|
|NxxH 17000 Oe||120 C/248 F|
|NxxSH 20000 Oe||150 C/302 F|
|NxxUH 25000 Oe||180 C/356 F|
|NxxEH 30000 Oe||200 C/392 F|
|NxxVH 35000 Oe||230 C/446 F|
|NxxAH 35000 Oe||230 C/446 F|
The Properties of Neodymium Magnets
When neodymium is placed in a magnetic field, the atomic dipoles align. After being removed from the field, a portion of the alignment remains creating magnetized neodymium. Remanence is the flux density that remains when the external field returns from a value of saturation to zero, which is the residual magnetization. The higher the remanence, the higher the flux density. Neodymium magnets have a flux density of 1.0 to 1.4 T.
The remanence of neodymium magnets varies depending on how they are made. Sintered neodymium magnets have a T of 1.0 to 1.4. Bonded neodymium magnets have a 0.6 to 0.7 T. Properties of Neodymium Magnet
After neodymium is magnetized, it does not return to zero magnetization. To get it back to zero magnetization, it has to be driven back by a field in the opposite direction, which is called coercivity. This property of a magnet is its ability to withstand the influence of an external magnetic force without being demagnetized. Coercivity is the measure of the intensity needed from a magnetic field to reduce the magnetization of a magnet back to zero or the resistance of a magnet to be demagnetized.
Coercivity is measured in oersted or ampere units labeled as Hc. The coercivity of neodymium magnets depends on how they are manufactured. Sintered neodymium magnets have a coercivity of 750 Hc to 2000 Hc, while bonded neodymium magnets have a coercivity of 600 Hc to 1200 Hc.
The density of the magnetic energy is characterized by the maximum value of flux density times the magnetic field strength, which is the amount of magnetic flux per unit surface area. The units are measured in teslas for SI units and its Gauss with the symbol for flux density being B. Magnetic flux density is the sum of the external magnetic field H and the magnetic body magnetic polarization J in SI units. Properties of Neodymium Magnet
Permanent magnets have a B field in their core and surroundings. The direction of the B field’s strength is attributed to the points inside and outside the magnet. A compass needle in a B field of a magnet points itself toward the field direction.
There is no simple way to calculate flux density of magnetic shapes. There are computer programs that can make the calculation. Simple formulas can be used for less complex geometries.
The intensity of a magnetic field is measured in Gauss or Teslas and is the common measurement of a magnet’s strength, which is a measure of the density of its magnetic field. A gauss meter is used to measure a magnet’s flux density. The flux density for a neodymium magnet is 6000 Gauss or less because it has a straight line demagnetization curve.
The curie temperature, or curie point, is the temperature at which magnetic materials have a change in their magnetic properties and become paramagnetic. In magnetic metals, magnetic atoms are aligned in the same direction and reinforce each other’s magnetic field. Raising the curie temperature changes the arrangement of the atoms.
Coercivity increases as the temperature increases. Though neodymium magnets have high coercivity at room temperature, it goes down as the temperature rises until it reaches the curie temperature, which can be around 320o C or 608o F. Properties of Neodymium Magnet
Regardless of how strong neodymium magnets may be, extreme temperatures can alter their atoms. Prolonged exposure to high temperatures can cause them to completely lose their magnetic properties, which begins at 80o C or 176o F.
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