Magnet BASIC INFORMATION

Magnets are manmade from ferromagnetic materials taken from the earth such as iron, cobalt, nickel, neodymium and samarium. However, there is a ‘natural’ magnet called Loadstone.  This naturally magnetised piece of magnetite does attract iron. Although it has to be technically classed as a magnet don’t expect the same performance as manmade magnets.

There are 3 classifications of magnetic metals:

Ferromagnetic: These are considered to be truly magnetic with a strong attraction to magnets

Paramagnetic: These metals only have a weak attraction to magnets

Diamagnetic: These metals display a slight repulsion to magnets

Ferromagnetic Metals include Iron, Nickel, Cobalt, Steel, Some Stainless Steel, Rare earth Metals including Neodymium, Samarium and Gadolinium.

In magnet manufacture, ferromagnetic materials are exposed to a magnetic field using an electric current. Magnetising fixtures are used to direct the electric current through metal material, electrons within the metal are polarised which makes the material magnetic.

There are three types are magnets:

Permanent magnets: These magnets have a constant magnetic field and do not need any other source of magnetism or electrical power

Temporary magnets: These magnets appear to behave as a magnet but only when close to something with a magnetic field.  When the source of the magnetic field is removed then they no longer have the characteristics of a magnet.

Electro-magnets: These magnets need a source of electricity to perform as a magnet.

Magnetisation is the process that turns a ferromagnetic material into a magnet.  The level of magnetisation can be measured by the strength of the magnetic field over a given area.

The strongest permanent magnets are Neodymium (Nd) magnets. Neodymium magnets are from the family of Rare Earth Magnets and are manufactured from a magnetic material consisting of neodymium, iron and boron forming the commonly seen structure of NdFeB.  Neodymium magnets offer incredible performance from a very small volume of magnet. They are available in many different grade, N55 is the highest grade available whereas the grades N42 and N52 are most readily available.

The two key features of a permanent magnet are that they always produce their own magnetic field without the need of any other source of magnetism and that magnetic field is there all the time, it can never be switched on or off.

Permanent magnets are made from Ferromagnetic materials including, Iron, Nickel, Cobalt, Steel, Rare earth Metals including Neodymium, Samarium and Gadolinium.

As long as a permanent magnet is not exposed to conditions that would affect its magnetism it will last for many, many years. A neodymium Magnet for example would only lose about 5% of its magnetism over a 100 year period. Things that can affect a permanent magnets magnetism include, high temperatures, demagnetising fields and corrosion.

A permanent magnet produces its own magnetic field which is always present and cannot be switched on or off.

An electromagnet creates its magnetic field by using a wire-wound coil which requires a source of electricity.

The magnetic field is the area around a magnet where its magnetic force is exerted.  In other words, it is the area around the magnet where the magnet is effective… move outside of the magnetic field and there is no magnetic force and the closer you get to the pole within the magnetic field the stronger the magnetic force.

Although invisible, the magnetic field of a magnet can be simply demonstrated by using iron filings and it can be very accurately simulated using complex modelling software.

A magnet’s strength can be measured in several ways, one of which is to measure the intensity of its magnetic field and this is measured in Gauss.  A specialised measuring device called a gauss meter is required.  A probe is placed directly onto the surface of one of the magnet’s poles and a reading is given.

In magnet manufacture, ferromagnetic materials are exposed to a magnetic field using an electric current.  Magnetising fixtures are used to direct the electric current through metal material, electrons within the metal are polarised which makes the material magnetic.  Please see our technical pages for more in-depth details of how specific magnets are manufactured.

Non-Ferrous metals are metals or alloys that do not contain iron and have benefits such as low weight, higher conductivity, resistance to corrosion and of course they are non-magnetic.

Yes. Ferrous metals are defined as any metal that contains iron and it is this iron content that enables a magnetic field to attract.

Technically you cannot ‘block’ magnetic fields however you can redirect the magnetic field lines which is commonly known as ‘shielding’.  You need to offer the magnetic field lines a preferred path by introducing a material of high permeability around the area you wish to shield.  The field lines find the easiest way to travel and therefore will keep within the material of high permeability.  This can be seen in action on Pot Magnets or placing keeper plates on the poles of magnets.

There are 5 main types of magnetic materials as follows;
1 – Alnico
2 – Ferrite
3 – Neodymium Iron Boron
4 – Samarium Cobalt
5 – Magnetic rubber

Within each type of material, there are many grades and variations to provide a variety of different magnetic properties.

If a magnet is stored away from power lines, other magnets, high temperatures and other factors that adversely affect the magnet, it will retain its magnetism essentially forever.

Expand/Heat/Radiation/Strong electrical currents in close proximity/Other magnets in close proximity to the magnet/Neo magnets will corrode in high humidity environments unless they have a protective coating.

Once a magnet is fully magnetized, it cannot be made any stronger – it is “saturated”.

Most commonly Gaussmeters which measure the strength in Gauss or Pull-Testers which measure in kgs or pounds.

They are the surfaces from which the invisible lines of magnetic flux emanate and connect on return to the magnet.

Two types – permanent and electro magnets. Permanent magnets emit a magnetic field without the need for any external source of power. Electro Magnets require electricity in order to behave as a magnet.

Neodymium-Iron-Boron types are the strongest. However at 150 degrees and above Samarium Cobalt can be stronger.

MAGNET PERFORMANCE

There are actually many ways in which you can determine the strength of a magnet:

  • Maximum Energy Product – Measured in Mega Gauss Oersteds (MGOe), the higher the Maximum Energy Product the greater the magnetic field of the magnet.
  • Coercivity – Measured in Oersteds (Oe), measures the resistance of a magnetic material to demagnetisation.
  • Remanence – Measured in Gauss is the residual magnetism left behind in a ferromagnetic material after magnetisation. The higher the value the stronger the magnet.
  • Pull Strength – Measured in kilograms is one of the easiest ways to compare the strengths of various magnets. It is quite simply the force required to separate the face of the magnet from a perfectly flat, steel surface.

If a magnet is fully magnetised then you will not be able to make it stronger as it has reached a saturation point.

Stacking magnets on top of each other will effectively create a bigger magnet with more performance.

Only in examples where magnets have been demagnetised could you ever increase their strength.

Yes, they can which is why it is important to source the right magnet for your application.  Here are some of the ways in which magnets can lose their magnetism:

  • Heat – Magnets will lose their magnetism if they are exposed to heats above a point known as the Curie temperature. Different types of magnets offer hugely different operating temperatures.
  • Demagnetising Magnetic Field – the Coercivity of a magnet is its ability to withstand being demagnetised by an applied magnetic field. This could be from another magnet or a solenoid.  Neodymium and Samarium Cobalt magnets have a high coercivity and therefore will demagnetise less easily than Alnico or Ferrite magnets for example.
  • Shock – Mainly seen in Alnico Magnets, these magnets can be easily demagnetised if dropped or hit with a hammer as the energy is transmitted through it.

In theory yes they do however if they are not exposed to conditions that may demagnetise them magnets will keep their strength for a long time. A Samarium Cobalt (SmCo) magnet will take approximately 700 years to lose half its strength for example.

Magnetic Force obeys an Inverse Square Law with distance which can be a little complex to follow but here are some simple examples based on moving the distance between two magnets:

  • Distance Doubled | Force is now a quarter the original value
  • Distance Halved | Force is now four times the original value
  • Distance increased by five times | Force is now one twenty-fifth the original value

Ferromagnetic Metals are the single most group of metals that are attracted to magnets. Some of the more common ferromagnetic metals include iron, nickel, cobalt, but also alloys that contain ferromagnetic metals – steel being an obvious example.

In order for a magnet to deliver its optimum performance then it requires conditions.  In real-world applications this very rarely happens so here are the things to look out for that will affect a magnet’s performance:

  • Air Gaps – This is the introduction of any non-magnetic material between the face of the magnet and another magnet or ferrous object. This can literally be a gap of air in some instances but also think about painted, rusty, dirty and uneven surfaces.
  • Material Thickness – If you are applying a magnet to a steel surface then the thickness of the steel needs to be thick enough to absorb all the magnetism. If you apply a strong magnet to a piece of think steel sheet for example it will not clamp firmly as the majority of the magnetism is not absorbed.
  • Material – Mild Steel is the perfect material for a magnet to attract to. Other metals although magnetic have a lesser ability to conduct magnetism.
  • Temperature – Exposing a magnet to temperatures above its operating limit will cause it to permanently lose performance. Neodymium in its most standard form must not exceed 80°C for example.
  • Corrosion – It a magnet is used in outdoor applications there is a possibility that its coating may become damaged which will expose the magnet and cause it to corrode which will result in a loss of performance. Samarium Cobalt and Ferrite magnets are both perfect for outdoor applications as they do not corrode.
  • Sheer Force – When a magnet is fixed to a surface in a vertical position its performance will be approximately 1/5th of its stated performance therefore a magnetic with a higher pull force may be required. However, rubber-coated magnets increase friction levels and make a significant difference in this application.

Our advice is always to keep magnets away from any electrical or electronic device as a general rule as you never know what is inside each and every device.

Magnetics has historically been linked to damaging storage devices based on magnetic storage which can include a credit card strip, a hard drive, a floppy disc etc…  However, most phones and tablets use non-magnetic storage today so this is no longer the issue it once was.

Newer devices do contain critical components that can be sensitive to magnetism.  It is likely that you would need to expose it to the field of a very strong magnet but none the less there is a risk of damage.

Yes, the main risk to humans lies in the misuse of magnets.

We see for sale on the internet incredibly large neodymium magnets that are sold to the general public.  These magnets are incredibly dangerous and can cause horrific injuries … nothing can prepare you for the devastation caused by two of these magnets attracting each other unexpectedly.  This is why we do not sell magnets above a certain size to the general public.

If part of your body is caught between two attractive magnets then pinch injuries can be caused, the stronger the magnets the worst the injuries will be.

As small neodymium magnets have been more widely available they can easily get into the wrong hands including children.  If swallowed these magnets can cause life-threatening injury and will require surgery to be removed.

Heart pacemakers are also adversely affected by magnets and wears of such should not come into contact with magnets.

Ferrofluid is a very special liquid that is magnetised when brought into the presence of a magnetic field.  The Ferrofluid created wild, spikey shapes and patterns as it is in close proximity to a magnet. Most pictures of Ferrofluid depict it with a very ‘spikey’ shape which is caused as the ferrofluid forms the most stable shape it can to minimise the total energy of the system, this is known as normal-field instability.

Provided that the material has not been damaged by extreme heat, the magnet can be re-magnetized back to its original strength.

NEODYMIUM, POT, RARE EARTH MAGNETS

Yes, in fact, Neodymium Magnets are THE strongest magnets available.  Not only do they offer the highest levels of magnetism but they also offer the highest levels of demagnetisation too.

Neodymium Magnets are available in different grades, the higher the number the stronger the magnet.  N42 and N52 are most common but N55 is the strongest, commercially available grade.

Neodymium, the same as all permanent magnets will last for 100’s of years if kept in optimum conditions.  Permanent magnets are estimated to lose less than 5% of their magnetism every 100 years.

It is worth noting that if Neodymium magnets not kept in optimum conditions their magnetic performance will be damaged.  You must never exceed the maximum operating temperature of a magnet as this will damage it.  Neodymium magnets are also extremely corrosive and if the surface coating of the magnet is compromised then the magnet may corrode which will also damage the magnet.

Neodymium, the same as all permanent magnets will remain magnetised for 100’s of years if kept in optimum conditions.  Permanent magnets are estimated to lose less than 5% of their magnetism every 100 years.

Rare Earth Magnets are the collective name for permanent magnets made from alloys containing rare-earth elements.

They are the strongest permanent magnets available delivering incredible performance from small volumes.

There are two types of rare earth magnets:

  • Neodymium Magnets (NdFeB)
  • Samarium Cobalt Magnets (SmCo)

Neodymium magnets are stronger than Samarium Cobalt magnets whereas Samarium Cobalt magnets offer much higher operating temperatures and higher resistance to corrosion than Neodymium magnets.

Neodymium magnets are available in many different grades but most commonplace are N42 and N52 grade magnets.

Standard Neodymium magnets have a max operating temperature of 80°C and are available in different strengths.  These magnets are prefixed with the letter ‘N’ followed by a number, the higher the number the stronger the magnet.  N35 is the starting point and increases through to N52 as standard.  The number relates to the Maximum Energy Product of the magnet.

Neodymium can also be manufactured to operate at higher working temperatures and these magnets are identified with a different letter or letters at the end of the code:

  • M = 100°C
  • H = 120°C
  • SH = 150°C
  • UH = 180°C
  • EH = 200°C
  • AH = 230°C

A pot magnet is simply a permanent magnet that is housed in a steel case or shell which is referred to as a pot.  Pot magnets generate a greater hold force than the magnet on their own as the pot ensures that the magnetic force is contained within the pot on the face of the magnet.  The magnetic field is effectively concentrated in one area which makes them perfect for operating over air gaps.

Pot magnets can use a wide range of different magnets including Alnico, Ferrite, Neodymium and Samarium Cobalt.

Pot Magnets are available in different formats offering a wide range of fixing methods utilising a number of different fixing types including Countersunk Screws, Bolts threaded bar etc…

As Pot Magnets are available with such a wide range of magnet material types, fixing types and cases finish they are extremely useful across many different applications:

  • Pot magnets are widely used in the exhibition and shopfitting industries for holding and hanging applications.
  • Shipbuilding use magnets to temporarily hold cabling to the steel structure during build phases.
  • Jigs
  • Recovery applications
  • Doorstops etc…

MAGNET APPLICATIONS AND USES

Magnets can be a very useful thing to have around but there are many applications that rely on magnets that have become part of our daily lives, some of them may surprise you…

  • Computers
  • Speakers
  • Radios
  • Televisions
  • Food processing to make sure our food is safe
  • Wind Power generators
  • MRI Scanners
  • Mobile phones
  • Credit Cards
  • Vacuum Cleaners
  • Washing Machines
  • Electric Cars
  • Anything with an electric motor…the list goes on and on…

Magnets are used throughout the home but most of the time you don’t even know they are there.  Some uses are more critical than others but here is a selection of the popular items that use magnets in the home:

  • Electric Cars
  • Burglar Alarm
  • Cat Flap
  • Telephone
  • Smart Phone
  • Computers
  • Speakers
  • Cupboard doors
  • Microwave oven
  • Mixer
  • Vacuum cleaner
  • Therapy magnets
  • Handbag clasps
  • Doorstops etc…

The type of glue required will very much depend on the strength of the magnet and the surface you are wanting to adhere it to.  Strong adhesives are generally required such as two-part epoxies and cyanoacrylates (super glues).  We stock two different cyanoacrylates, one for use on Wood and Paper and the for use on Metals.

No…you should never attempt to cut or drill a magnet.  Most magnets are very brittle once they emerge from the manufacturing process and any attempt to cut or drill the magnet will inevitably cause it to break.

If you require a very specific size of magnet or require a magnet with a hole or holes then please contact us as we can produce magnets to your exact specifications for low costs and low volumes.

Yes, however, the reality of it happening during normal day-to-day life is quite rare.

Credit cards incorporate a magnetic substance that forms the ‘magnetic strip’ on the card.  This is then covered by a thin but very tough and durable film of plastic.  Most magnets we encounter during the day are not even visible and are built into devices such as smartphones, tablets, speakers etc…and so your credit card would not get close enough to the magnet and the magnet would not probably be strong enough to cause an issue.

If you were having an MRI scan or were handling large, powerful magnets then, naturally you would ensure your credit card was out of the way.

Although the risk not high we would always recommend keeping your credit card away from magnets as ultimately, they can be damaged by magnets.

We have 3 different types of magnets that lend themselves perfectly for this application:

  • Ferrite Disc Magnets – Low cost with a reasonable holding force. Simply glue in place.
  • Flexible Magnetic Rubber – Low Cost and extremely versatile. Flexible rubber is available in sheets for you to cut to size, pre-determined kiss cut shapes to save you time and these can be either glued in place or can be purchased with self-adhesive backing.
  • Neodymium Disc Magnets – This is the magnet if your design requires a small but powerful magnet. They are available in a vast array of sizes and strengths and can be simply glued in place.  They are also available with self-adhesive backing.

There are many magnets available that are dedicated for use on wipe boards, whiteboards and dry-wipe boards.

Typically, ferrite notice board magnets are very popular due to their low cost, bright colours, good strength and ease of handling.

These magnets can come in a vast range of sizes and shapes allowing you to select the perfect magnet for your requirements.  Neodymium variations are also available for applications where a great force is required.

Flexible magnetic rubber is also a good option.  These can be purchased in a larger number of different shapes, sizes and colours including squares and circles which are perfect for planning boards.  Flexible magnetic rubber grid lines are also available in a number of colours and thicknesses which again are perfect for creating planning boards.

Got another question? Please contct us with [email protected].