"Dictionary"

We have put together a small keyword index for you with a selection of the most important terms relating to magnetism:

AlNiCo / Alnico

Made-up word, consisting of three abbreviations. This refers to alloys made primarily of aluminum (Al), nickel (Ni) and cobalt (Co), as well as iron and copper. AlNiCo permanent magnets are manufactured by casting technology or sintering and were the first permanent magnets used for mass production in the 1930s. They are the most heat-capable of all types of magnets (unpainted up to at least 450°C, some even significantly higher). The disadvantage compared to ferrite and neodymium magnets is their relatively low magnetic stability. Alnicos are now used in measurement and control technology, in sensor construction, in guitar pickups, in loudspeakers as well as in research and science (including in schools).

Anisotropy

Greek: anisos-tropos = english: unequal direction. Opposite of isotropy (see below).

Opposite of isotropy (see below). A magnet is anisotropic if its magnetic properties act independently of its orientation, i.e. without a preferred direction.If a magnet does not have a preferred direction, the effect is less.Ferrite magnets with a magnetization strength of Y10, such as our ferrite cube 50x15x06 mm, are anisotropic and therefore have a low effect - this deliberately low force was chosen so that the magnet can be used relatively safely, for example in primary schools.

axial

The most commonly used magnetization direction, which runs along the main axis.This means that the magnets are magnetized through the thickness and their poles can be found in a specific place:For blocks, disks and rings on the large surfaces, for rods at their ends, for balls and cubes on two opposite sides.The majority of our magnets are axially magnetized.

Curie temperature

Named after the French physicist Pierre Curie, abbreviated TC or ϑC.The Curie temperature refers to the point at which the ferromagnetic or ferroelectric properties of a magnet come to a complete standstill.Above this temperature, magnets are only paramagnetic, i.e. magnetic in the vicinity of another magnet, but not in themselves.

Diamagnetism

Describes the phenomenon that a matter that is exposed to an external magnetic field develops a magnetic field that is opposite to this external magnetic field. A diamagnetic effect occurs with every type of matter; However, this is usually only weak.Only diamagnetism occurs in a few substances; these materials are called diamagnets.The strongest diamagnet (apart from superconductors) is pyrolytic graphite, which you can also find in our shop.

diametrically

Less common direction of magnetization that runs from the inside to the outside of a material (rather than along an axis). Magnetic rods, for example, do not have their poles at the two ends, but on the surfaces.Other special magnetization directions: radial or multipolar.

Energy product

Is given in megaGauss-Oersted, MGOe, or kJ/m³. The amount of magnetic energy that this refers to depends on the product of the magnetic flux density, the magnetic field and the volume of the magnet. This results in the amount of magnetic energy stored in a permanent magnet.

Demagnetization

Process in which the magnet's magnetic field disappears. A magnet is demagnetized through improper use (e.g. overheating) or controlled. If the magnetic material is not destroyed during demagnetization, the magnetic field can be restored by re-magnetization.

Field lines

These are imaginary lines that illustrate the magnetic field of a magnet. They are made visible in schools, for example, by spreading iron powder on a magnet covered with a sheet of paper, which accumulates depending on the strength of the magnet's magnetic effect.

Field strength

Formula symbol: H. Magnetic field strength determines the ability of a permanent magnet to generate a magnetic field at a specific point.

Ferrite (ceramic)

The ferrite used for ferrite magnets belongs to the group of ceramic materials. Hard ferrite permanent magnets are made of iron oxide and also either strontium (Sr) or barium (Ba). Ferrites are usually produced by sintering and are the cheapest and most widely used permanent magnet material. They are used as cores in coils or transformers, can be found in loudspeakers, sorting systems and motors, but also in classic “pinboard magnets”.

Ferromagnetism

Generic term for all substances that have a greater or lesser magnetization after the application of an external magnetic field.

Flux density

Density is the ratio of the mass of a body to its volume. The flux density, in turn, describes the strength of the magnetic flux that runs through a surface.

Gauss

After Friedrich Gauss, mathematician. Unit of measurement for magnetic flux density, see also Tesla (after the physicist Nikola Tesla). 10,000 Gauss = 1 Tesla.

Holding force

The holding force is not weakened even after years of use. Strong holding force, corrosion resistant, protects against surface damage. To determine the holding force, place a magnet on an optimal holding surface (mild steel, at least 1 cm thick). A scale is used to record the point at which the magnet detaches from its surface. The value determined at that moment describes the holding force of a magnet. However, this is determined under optimal conditions (room temperature, humidity, etc.), which cannot be achieved in daily use. We therefore always specify the holding force with moderate values. It is not permitted to determine the holding force using a second steel plate that is attached to the magnet (as sometimes shown in the picture);These “measuring” procedures are dubious and the only way to “determine” such gigantic alleged holding forces as they are sometimes offered on the Internet...

Hysteresis

Ability of a magnet to respond to an external magnetic field. In relation to this external magnetic field, the magnetization of the magnet increases rapidly. After the external magnetic field is switched off, the magnetization decreases with a delay. This can be represented with the hysteresis loop or hysteresis curve. The remaining magnetization is called remanence.

Isotropy

Greek: isos-tropos = German: same direction. Isotropic magnets are manufactured in a magnetic field, giving them a preferred direction of magnetization. Compared to anisotropic magnets, the energy density is approximately 300% higher. The coercivity is high in relation to the remanence.

Coercive field strength

Abbreviation: Hc (H = magnetic field strength, c = Latin coercere, German = to keep within limits, to restrain, to force). The magnetic coercivity is the strength required to completely demagnetize a magnet. The value of the coercivity is given either in kA/m (kiloamperes per meter) or in Oe (Oersted, after the physicist Hans Christian Ørsted).

Coercivity

Again from Latin coercere = to force. Coercivity means the resistance of a magnetic material to demagnetization or remagnetization. The higher the coercivity of a magnet, the harder it is to demagnetize. SmCo magnets, for example, have high coercivity.

Levitation

Latin levitas = German lightness. Levitation refers to the free floating of an object with the help of a force. Air cushion boats, for example, float using compressed air. In magnetism, the magnetic force (repulsion) can be used to counteract gravity and cause objects to levitate, such as pyrolytic graphite. However, permanent free floating of one magnet above another is impossible without a guide rail, since stable equilibrium positions cannot be created with static fields (Earnshaw's theorem).

Lorentz force

Named after the mathematician and physicist Hendrik Antoon Lorentz.The Lorentz force is the force that acts on moving charges in magnetic fields. If you hold a current-carrying conductor in a magnetic field, it will move to the side due to the Lorentz force.

Air gap

Describes the distance between two magnets or between a magnet and a substrate, e.g. a steel plate. This air gap can be a gap between the magnet and steel, but can also be filled with non-magnetic material such as wood, bubble wrap, plastic, etc. Every air gap between two magnets or magnet and substrate significantly reduces the magnetic effect (with an air gap of one millimeter, depending on the shape of the magnet and magnetization, the holding force can be halved). One of the reasons we pack magnets with as much material is to keep the air gap to the cardboard as large as possible so that the magnetic force does not penetrate through the cardboard wall. Magnets that adhere too strongly can be weakened in their holding power by creating an air gap, e.g. by covering them with felt. Conversely, magnets that have to overcome air gaps (e.g. in a glass pinboard where the magnetic surface is behind 4-8 mm thick glass) must be sufficiently strong to be able to bridge this air gap.

Magnetic field

A magnetic field arises around a current-carrying conductor (electromagnet) or exists permanently around a permanent magnet (like the ones we offer). It is not visible but can be made visible with the help of iron powder. The Earth has the largest magnetic field, which is, in a sense, a huge (weak) bar magnet.

Magnetic shielding

Magnetic fields also affect electronic devices. Some areas (e.g. aerospace, military transmitters) require so-called magnetic shielding. This does not mean eliminating the effect of individual magnets, but rather preventing the influence of magnetic fields (both low-frequency as well as electric and static fields) over a large area. This shielding is achieved by large magnetic shields made of μ-metal (mu-metal), a highly specialized metal developed for shielding.

Magnetic Earth Poles

In a sense, the Earth is a huge bar magnet with both ends at the south and north poles. The Earth's magnetic field extends from the poles. However, from a physical point of view, the geographical south pole is the magnetic north pole and vice versa. For this reason, the north pole of every magnet is attracted to the geographical north pole, because from a physical point of view the latter is a magnetic south pole.

Magnetic dipole

A permanent magnet always has two poles, a north and a south pole. The alignment of the elementary magnets within a magnet means that a magnet must necessarily have two poles, i.e. it is a dipole. If you separate a magnet in the middle, you don't get an isolated north or south pole, but rather each of the two parts is again a dipole. See also: magnetization.

Magnetization

There are many small districts in a piece of iron: Everyone behaves like a magnet, so it has a north and a south pole. That's why they are called elementary magnets.In a piece of metal the elementary magnets are disordered and thus cancel out the magnetic effect to the outside.When you create an external magnetic field, the elementary magnets all align in the same direction: the workpiece is magnetized. When the best possible alignment is achieved, this is referred to as “magnetic

Degree of magnetization

Magnets can be magnetized to different strengths. As a result, they have different magnetic strengths.How strong a magnet is depends on its shape, size, possible coatings and (only then) its degree of magnetization.For neodymium, this is represented by a letter-number combination, usually an N plus the numbers 35-52. The letter denotes the temperature resistance (N, M, H, SH, UH, EH), the number the magnetization strength.In the case of ferrites, there is also a letter-number combination to indicate the magnetization, according to the chinese standard (the manufacturer's name) a Y plus the numbers 10-35. The US standard uses the letter C, in europe the letters HF are also used.

Magnetization direction

The direction of magnetization indicates where the poles of a magnet are located (for disks, rods, rings usually on the circular surfaces, for cuboids and cubes usually on the large surfaces; for alnico magnets this often differs). The most common direction of magnetization is axial (see above); other directions of magnetization are also given as diametrical and radial.

Maximum operating temperature

Each type of magnet has a specified maximum operating temperature up to which it can be heated. If a magnet is (permanently) overheated, it will be partially or completely demagnetized, depending on the temperature and duration. The maximum operating temperature for neodymene (unless stated separately) is approx. 80°C, for ferrites it is approx. 250°C and for alnicos (depending on the material composition) it is 400-500°C.

Newton

Named after the naturalist and philosopher Sir Isaac Newton. A Newton as a unit of measurement describes the physical force and is a derived quantity depending on the base units kilogram, meter and second. The holding force of a magnet is given in kg or N. 10N ≈ 1kg.

North Pole

The north pole of a magnet gets its name from the fact that it is attracted to the geographical north pole of the Earth. In a physical sense, the geographical north pole is a magnetic south pole. This means that, although the north pole of a magnet is attracted to the geographical north pole of the earth, the rule of attraction of unequal poles also applies here.

Oersted

Named after the physicist Hans Christian Ørsted. Old unit of measurement for the magnetic field strength H.

Permanent magnets

Also: permanent magnets. These are materials that are permanently magnetic in their own right, namely the ferrite, neodymium or alnico magnets we offer. They have generally been magnetized by an external magnetic field (although they also occur in nature and are already magnetic) and retain their magnetic effect unless this is canceled out by external influences (overheating, violent mechanical shock or strong surrounding magnetic fields). Unlike electromagnets, permanent magnets do not require electricity to generate a magnetic field, but conversely cannot be “switched off” (except through the destruction or targeted demagnetization mentioned above). In principle, magnets do not lose their magnetic force when used properly. Alnicos are most likely to lose magnetic force, while neodymium has been calculated to lose only a fifth of their magnetic force over a period of 1,000 years.

Permeability

Sign μ. This number indicates how many times more magnetic lines of force pass through the body than were previously present in the same place without the body.Determines the permeability of matter to magnetic fields.Permeability is also known as magnetic conductivitySubstances with a permeability of μ > 1 are called paramagnetic (for example platinum, aluminum, air).Substances with a permeability of μ >> 1 are called ferromagnetic (for example iron, cobalt, nickel).Substances with a permeability μ < 1 are called diamagnetic (for example silver, copper, bismuth, pyrolytic graphite).

Remanence

Also residual magnetization, remanent magnetization. Latin remanere = to remain, to remain behind. Remanence is the residual magnetization that a magnet that was previously magnetized by an external magnetic field retains after this external magnetic field has been removed. The remanence indicates how strong the remaining magnetization of a magnet is.

Samarium Cobalt

Fourth type of magnet (SmCo magnets), consisting primarily of samarium (Sm) and cobalt (Co). Like neodymium, samarium is a rare earth element. Typically, two different alloys are used to make SmCo magnets. The advantage of SmCo magnets lies in their good temperature properties (max. operating temperature approx. 350°C), the extremely difficult demagnetization and the higher holding power compared to ferrites and Alnicos. However, they do not come close to the power of neodymenium and are simply very expensive.

Rare Earth

Also: rare earth metals or rare earth elements. These can be found in the 3rd group in the periodic table of chemical elements (except actinium) as well as in the lanthanides = 17 elements (including cerium, neodymium, samarium, lanthanum, yttrium, erbium). They are not called “rare” earths because they are rare, but because they were first found in rare minerals. The only rarely occurring rare earth element is promethium; Neodymium, for example, is extremely common. Well over 95% of rare earths are mined in China, as well as in India, Brazil, Malaysia, Australia and the USA. Preparations are currently being made for mining in areas with known high deposits (including CIS countries, South Korea/Vietnam).

South Pole

The south pole of a magnet gets its name from the fact that it is attracted to the geographical south pole of the Earth. In a physical sense, the geographical south pole is a magnetic north pole. This means that, although the south pole of a magnet is attracted to the geographical south pole of the earth, the rule of attraction of unequal poles also applies here.

Tesla

Unit for magnetic flux density named after Nikola Tesla. One Tesla is equal to one volt second per square meter or 10,000 gauss. 1 T = 1Vs/m2 = 10,000 G.

Sources: Spektrum der Wissenschaft, Lexikon der Physik, 1998

physikon.de, Physik-Lexikon

Duden, Basiswissen Schule, Physik Abitur, 2011

Was ist was, Band 39: Magnetismus, 2005

dtv-Atlas Physik, Band 2: Elektrizität, Magnetismus, Festkörper, Moderne Physik, 2000

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