When magnet material is pressed into a magnetic field, the magnet material is called preferentially directed and anisotropic. Magnetizing anisotropic magnet material can only take place in the preferential direction.
See magnetic induction
See maximum energy density
Coercivity, normal: HcB
The necessary field strength to turn the magnetic induction in magnet material to 0.
Coercivity, intrinsic: HcJ
The necessary field strength to turn the polarisation of magnet material to 0.
Temperature above which the magnetisation disappears completely.
Demagnetisation curve (2nd quadrant of the hysteresis curve)
The demagnetisation curve of magnet material is determined by placing the magnet material in a closed system and inducing a magnetic field using spools, that first magnetizes the magnet material to satiation (+H) and subsequently demagnetizes (-H).
See magnetic induction
Permanent loss of magnetism by, for example, a too high temperature or oxidation. This loss is irretrievable.
Magnet material that is not pressed into a magnetic field is called isotropic. It is possible to later magnetize the magnet material in all directions.
See magnetic polarisation.
Magnetic induction, B
Magnetic arrangement in material as a consequence of a magnetic field (H) and/or magnetic material (J) or: the number of magnetic field lines per unit area. Units: among others T and G.
Magnetic polarisation, J
Material contribution to the magnetic induction. Units: among others T and G.
Magnetic field strength, H
Magnetic strength as a consequence of magnetic induction.
Maximum energy density BH max
Largest possible product of B and H on the demagnetisation curve. In general it applies that the larger the BHmax of the magnet material is, the smaller the volume can be.
Maximum usage temperature
Indication of the maximum temperature at which the magnet material can be used with limited irreversible losses (see Operating point, operating line).
Capacity of material to conduct magnetism. The permeability of vacuum (μ0) is 1,256?10-6 T/(A/m) or 1 G/Oe.
Magnetic induction in magnet material at field strength zero (H=0) and after complete satiation.
Temporary loss of magnetism due to, for example, changes of temperature. This loss can be recovered by cooling off and/or magnetizing again.
Temperature coefficients (Br and HcJ)
These indicate the reversible change of Br and/or HcJ in percentages in case of change of temperature. The values are, among other things, dependent on the type of material, the quality and temperature.
The field lines that leave the magnet return to the magnet through air (not ferromagnetic material).
Operating point / operating line
The operating point (Bm, Hm) of a magnet is the intersection point of the operating line with the B-H curve. For magnets with free poles and no external magnetic field the angle of the operating line compared to the B-axis is dependent on the relation between the length and diameter of the magnet;