# Permanent Magnets

List of terms

Anisotropisk – isotropisk:

When a magnetic substance is compressed in a magnetic field, this substance is called anisotropic. When the substance is not compressed in a magnetic field, it is characterised as isotropic. Later the isotropic substance can be magnetised in all directions, while anisotropic substances can be magnetised in the specifically focused direction. The remanence (Br) of an anisotropic substance is approximately the double value of the remanence of an isotropic substance. See figure 1.

Goudsmit monitors the dimensions of your magnet by using state of the art CNC measuring equipment.

General Features

B:

See magnetic induction

(BH)max

BR:

See remanence

Coercivity, normal HcB:

The necessary field power to create the magnetic induction in a magnetic substance o (see demagnetisation curve). The “-“ mark is often omitted in specifications. Units: A/m or Oe.

Coercivity, intrinsic HcJ:

The necessary field power to induce a polarisation of a magnetic substance o (see demagnetisation curve). The “-“ mark is often omitted in specifications. Units: A/m or Oe.

Curie temperature:

Temperature at which magnetisation disappears completely. Units are C and K among others.

Afmagnetiseringskurve af isotropisk og anisotropisk stof.​

(Second quadrant of the hysteresis curve).

Demagnetisation curve of a magnetic substance can be determined by placing the magnetic substance in a closed system by generating a magnetic field by means of coils. At first the substance is magnetised to the point of saturation. (+H) and then demagnetised (-H). The polarisation of the magnetic substance (J) is measured during the process. The magnetic induction B into the magnet is calculated using the following formula:

B=J+ou*H, where

J=polarisation of the substance (part of the substance)

Uo*H=part of the substance

​Demagnetisations curve.

Flux mass:

See magnetic induction.

​HcB:

See coercivity, normal.

HcJ:

See coercivity, intrincic.

Losses, which cannot be regained can be regenerated.

E. g. permanent loss of magnetism because of excessively high temperature.

Only re-magnetisation can regenerate the loss.

​Losses, which cannot be regained cannot be regenerated either.

E. g. permanent loss of magnetism because of excessively high temperature or oxygenation.

This loss cannot be regained.

Isotropic:

See anisotropic

​J:

See magnetic polarisation

Magnetic induction, B:

Magnetic alignment as a result of a magnetic power (H) and/or a magnetic power (J) or: The number of magnetic field lines per unit – the area. Units: Includes T and G.

Magnetic polarisation, J:

The part of a substance for the magnetic induction. Units include T and G.

Magnetic field power, H:

Maximum Energy Mass (BH) max:

Largest possible product of B and H on the de-magnetisation curve (see de-magnetisation curve). Generally this applies: The larger (BH) of a magnetic substance , the smaller volume. The “-“ mark is normally excluded in specifications. Units: kl/m3 and MGOe. For example: Volume of a GSN magnet can be +-10 times smaller than the volume of a GSF33H magnet and still have the same application.

General Features

Values can only be applied for comparison of substances. Mechanical stress: Because of fragility, it is not recommended to expose the magnets to magnetic stress.

The values of the substances are measured according to IE404-5 standard: The mechanical features mentioned in the table cannot be obtained for all forms and dimensions.

​Maximum application temperature:

The indication of the maximum temperature where the magnetic substance can be applied with a limited permanent loss (see Working point, Operating Line).

Permanent magnet:

A magnet, which completely or partially keeps its magnetism after magnetisation.

Permeability:

The capacity of the magnetic substance to conduct magnetism.

Permeability of vacuum (uo) is 12,56*10-6 T/(A/m) or 1 G/=Oe.

Figure 3: De-magnetisation curve and working point for all Neoflux magnets.

Remanence Br:

Magnetic induction in a magnetic substance when the field power is zero (H=0) and after saturation (see de-magnetisation curve). Units: Inclusive T and G.

Restorable Loss:

Temporary loss of magnetism because of changing temperature for instance.

Free Poles:

Field lines, which leave the magnet, return to the magnet through the air (no ferromagnetic substance).

Working Point / Operating Line:

2 de-magnetisation curves (only the normal curve) of random Neoflux substances in figure 3. Working point (Bm, Hm) of a magnet is the point where the working line crosses the B-H curve. For magnets with free poles and without external magnetic field the angle of the working line correlated to the B axis is dependable on the relationship between length and diameter of the magnet; L1/D1 > L2/D2.

Working line 1 is closer to the axis than the working line 2.

Partnering with Elektrokul A/S, Goudsmit UK can advice on a consultancy basis by means of EDB simulation. We apply the most advanced software to calculate your magnetic system.

Permanent magnets are also available in a steel pot (with a rubber protection upon request); these kinds of magnets have a magnetic field, which makes them a lot stronger.

An advanced product like a loud speaker needs a dust free magnet with the right with the right magnetic and mechanical features.

Our range of deliveries includes electro magnets.

Safety Instruction

Warning!

This package contains very strong, permanent magnets or magnetic systems.

There is a risk of serious damage if these magnets are not treated very carefully.

Please take a note of the following warnings:

Magnets must glide from one another in a cautious way in order to prevent fingers from getting stuck between them. It prevents damage of the surface treatment too. Use gloves if possible.

When you unpack the magnets, make sure that there are several meters of distance between you and any item made of iron.

The magnets must be kept away from any carrier of magnetic information, as for example credit cards, magnet bands, floppy disks, and all electronic equipment such as hearing aids, pacemakers, measuring- and control instruments and EDB machines. These items can be damaged by the extreme, high power magnet fields.

Never use magnets in explosive settings, because sparks can be ignited.

Before use, always wet the magnets to prevent spontaneous ignition. Always use cooling water, never work without it by processing of the magnets!

Always keep dust and processed parts after processing in water containing reservoirs or hermetically closed spaces in order to control the risk for spontaneous ignition.

Company Information

Elektrokul A/S

Snedkervej 2A

DK-4600 Køge

Denmark

Phone: ​+45 70 20 78 26

Fax: +45 70 20 78 23

E-mail: info@elektrokul.dk

VAT no / CVR: 27416764