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.

Most Common Grades of Neodymium Magnets
NxxNxxMNxxHNxxSHNxxUHNxxEH
N30N30MN30HN30SHN28UHN28EH
N33N33MN33HN33SHN30UHN30EH
N35N35MN35HN35SHN33UHN33EH
N38N38MN38HN38SHN35UHN35EH
N40N40MN40HN40SHN38UHN38EH
N42N42MN42HN42SHN40UHN33VH
N45N45MN45HN45SHN33AH
N48N48MN48H
N50N50M
N52

The approximate maximum working temperature of each grade is indicated below. The XX is the maximum energy product in MGOe.

Maximum Working Temperature of Each Neodymium Magnet Grade
Neodymium GradeMax Temp
Nxx 12000 Oe80 C/175 F
NxxM 14000 Oe100 C/212 F
NxxH 17000 Oe120 C/248 F
NxxSH 20000 Oe150 C/302 F
NxxUH 25000 Oe180 C/356 F
NxxEH 30000 Oe200 C/392 F
NxxVH 35000 Oe230 C/446 F
NxxAH 35000 Oe230 C/446 F
The Properties of Neodymium Magnet

The Properties of Neodymium Magnet

The Properties of Neodymium Magnets

Remanence:
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

Coercivity:
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.

Energy Product:
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.

Curie Temperature:
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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