Common Applications Of Neodymium Magnets

Hard disk drives

A hard disk drive records data by magnetising and demagnetising a thin film of ferromagnetic material on a disk. Each disk is separated into many tracks and sectors and each sector has many tiny individual magnetic cells which are magnetised by the drives read/write head when data is written to the drive. Hard drive heads are made from ceramic wrapped in a fine wire coil. When writing, the coil is energised, a strong magnetic field forms, and the recording surface adjacent to the gap is magnetised. 

Strong magnets are also used in the actuator that moves the read/write head into position.

 Audio equipment such as microphones, acoustic pick-ups, headphones and loudspeakers

Permanent magnets are used in speakers alongside a current-carrying coil which converts electricity into mechanical energy that moves the speaker cone that in turn changes the pressure of the surrounding air creating sound. Microphones work in reverse; a diaphragm is attached to a coil of wire which sits within a permanent magnet, when sound moves the diaphragm the coil moves too. As the coil moves through the magnetic field created by the permanent magnet an electrical signal is produced which is characteristic of the original sound.

Dentures

Tiny neodymium magnets can be used for attachments in corrective devices or for holding together replacement dentures where several teeth are missing. Because of their strength, even tiny neodymium magnets can be effective and when coated they have an increased resistance to corrosion.

Magnetically coupled pumps

Magnetically coupled pumps consist of a motor-driven shaft with an attached ring of powerful magnets and another smaller ring of magnets attached to another shaft connected to the impeller that sits within the larger ring of magnets. As the motor turns the drive shaft and one set of magnets, the magnetic field generated turns the other set of magnets which powers the impeller. With this type of motor there is no mechanical contact between the motor and the impeller.

Magnetically coupled pumps, or magnetic impeller pumps provide two main advantages over non-magnetic pumps. Because the impeller is connected to the driving magnets and shaft by magnetism alone, if the impeller is obstructed and stops turning the motor can continue to turn without burning out avoiding any lasting detriment to the motor. The second, is relevant to applications in which liquid could potentially seep into the motor unit (for example, a pond motor) as with a magnetically coupled motor you can completely separate the motor unit from the impeller, which is usually within a hermetically sealed case.

Door catches

Electric motors rely upon a combination of an electromagnet and a permanent magnet, usually a neodymium magnet to convert electric energy into mechanical energy. A generator is the reverse, it converts mechanical energy into electric energy by moving a conductor through a magnetic field.

Neodymium magnets are used in public, commercial and residential buildings to create magnetic door catches. Countersunk or pot magnets recessed into the surface of a door are used to attract another wall mounted magnet or steel disk. Strong neodymium magnets will easily hold the weight of a door and the leverage provided by the door means the magnets can be easily separated.

Motors and generators

Electric motors rely upon a combination of an electromagnet and a permanent magnet, usually a neodymium magnet to convert electric energy into mechanical energy. A generator is the reverse, it converts mechanical energy into electric energy by moving a conductor through a magnetic field.

Jewellery

Small magnets are used in the production of jewellery and for jewellery clasps. Counter-bored neodymium magnets with opposite poles on the counter-bored faces provide a secure hold and because neodymium is the strongest magnetic material in the world a magnet just 5mm in diameter can be effective.

Bearings

Magnetic bearings use the concept of magnetic levitation to support moving parts without physical contact. They are used to enable relative motion with very low friction and no mechanical wear even at incredible speeds. Bearings known as passive magnetic bearings use permanent magnets such as neodymium magnet while active magnetic bearings use electromagnets.

MRI scanners

MRI scanners produce a large magnetic field which aligns the protons in a human body in the direction of the magnetic field. Radio frequency waves are then directed at the body producing detailed internal images. Many ‘open’ MRI machines used in hospitals use large neodymium magnets, they literally help save lives.