Permanent Magnet: Know Definition, Examples, Properties, Types and Uses

Magnets are known for having the ability to attract and repel specific metal materials like iron and nickel. This isn’t always the case, though. Magnets occasionally lose their ability to attract or repel materials. Everything depends on the kind of magnet we were utilizing. Magnets are primarily divided into three different types according to their physical makeup and magnetic field source- Permanent Magnet, Temporary Magnet and Electromagnetic devices

In this article, we will be focusing on permanent magnets. Read on to learn more about its properties, types, uses, advantages and disadvantages.

What is a Permanent Magnet?

A permanent magnet is a magnet whose internal construction creates a lasting magnetic field inside of it. Even after the external magnetizing field is removed, they still retain their magnetic field. Hard ferromagnetic material with great retentivity and coercivity is what makes up a permanent magnet. Permanent magnets are made of iron, cobalt, nickel, steel, and some alloys of rare earth metals. Like every magnet, each permanent magnet produces a magnetic field that loops in a unique pattern around the magnet. The strength and size of the magnet have an impact on how large the magnetic field is. In a permanent magnet at room temperature, domains are partially aligned due to thermal agitation. 

The iron filings scattered around over a bar magnet, that are immediately orientated along the field magnetic lines of force, are the simplest way to observe a magnetic field produced by a permanent magnet. Although they might also be referred to as A and B, every permanent magnet contains two poles that are known as north and south. While opposing poles attract one another, like poles repel one another. A magnet’s repulsive poles must be kept together with a lot of work, whilst its attractive poles must be removed with effort.

One of the well-known examples of the permanent magnet is the refrigerator magnet.

Properties of Permanent Magnet

Attractive property

Ferromagnetic materials are difficult to demagnetize once magnetized. Its nature is referred to as a persistent magnet. The very same magnetic poles of two magnets will resist and push away from one another when they are in close proximity, while opposite north and south poles would attract and stick to one another. In other words, similar poles repel one another whereas dissimilar poles attract.

Directive property

According to the directional property of magnetism, a suspended magnet’s north and south axes will always point in the same general direction as the earth’s magnetic meridian.

Permanent Magnet Examples

Here are some common examples of permanent magnets:

• Alnico magnets - Made of aluminum, nickel, and cobalt. Very resistant to demagnetization. Often used in loudspeakers and motors.
• Ferrite magnets - Made of barium or strontium ferrite. Inexpensive and commonly used where high magnetic field strength is not required. Common in record players, magnetic strips, and refrigerator magnets.
• Neodymium magnets (NdFeB) - One of the strongest permanent magnet materials available. Made of neodymium, iron, and boron. Used in electric motors, hard disk drives, and magnetic fasteners.
• Samarium cobalt (SmCo) - A rare-earth magnet developed in the 1960s. Offers high strength and resistance to demagnetization. Used in military/aerospace applications and precision instruments.
• Ceramic magnets - Made from barium or strontium ferrite. Brittle but very inexpensive. Used in sensors, switch components, and magnetrons.

Types of Permanent Magnet

There are three types of permanent magnets. Let’s study them one by one.

Single-Chain Magnets

A fascinating class of molecule polymeric materials with slowly relaxing magnetism is known as single-chain magnets (SCMs). They enable a single polymer chain to exhibit magnetic hysteresis at low temperatures. The similarities are mostly obvious, despite the fact that their behaviour is reminiscent of more well-known magnetic flux particles and single-molecule magnets (SMMs). These are completely different from regular magnets and might theoretically provide a far denser storage medium than conventional magnets. Conventional magnets hold data at a magnetic domain level.

Rare Earth Magnets:

The majority of rare earth magnets are permanent magnets. They are composed primarily of an alloy consisting of elements from the lanthanide series and rare earth elements. Compared to ferrite magnets and alnico magnets, rare earth magnets produce a magnetic field that is significantly stronger.

Neodymium Iron Boron:

Another kind of rare earth magnetic substance is neodymium iron boron (NdFeB). With the exception of being more quickly oxidised and generally not having the same temperature resistance, this material shares many characteristics with samarium cobalt. Due to their high price, these materials are typically employed in extremely limited applications.

Samarium cobalt:

Samarium cobalt is a form of rare earth magnet material with greater magnetic strength and temperature endurance than Alnico or Ceramic material. It is also extremely resistant to oxidation. Samarium-cobalt magnets, which were first used in the 1970s, are still in use today.

Samarium cobalt magnets that have been sintered are fragile, prone to breaking, and may crack or chip when subjected to heat shock. Samarium cobalt magnets are utilized in situations where high temperature and corrosion resistance are essential due to the material’s expensive cost.

Magnetic Metallic Elements:

A magnet will draw magnetic materials near it, and they may even start to become magnetised. Metals make up the majority of magnetic materials. Metals that are magnetic include iron, nickel, cobalt, and steel, to name a few. Magnetism, however, is a complicated phenomenon. Steel and iron are not all magnetic.

The names of the rare earth elements that make up powerful rare earth magnets are used. However, these materials aren’t really ferromagnetic on their own.

Difference between Electromagnet and Permanent Magnet

The following table shows important differences between electromagnet and permanent magnet.

Parameter	Electromagnet	Permanent Magnet
Magnetism source	Electric current	Intrinsic magnetic properties of the material
Magnetic field generation	Magnetic field is generated when current flows through the coil winding	Magnetic field exists inherently without any external power source
Controllability	Magnetic field can be controlled by varying the electric current	Magnetic field cannot be controlled easily as it depends on material properties
Strength of magnetic field	Magnetic field strength varies as per the amount of current	Magnetic field strength remains constant
Applications	Motors, electromagnets, speakers, relays etc.	Refrigerator magnets, hard disk drives, earphones, electric guitars etc.
Examples	Solenoids, electro-magnets	Bar magnets, horseshoe magnets
Switching ability	Magnetic field can be switched on and off easily by switching the current on and off	Magnetic field cannot be switched on or off easily
Power requirement	Requires continuous power supply to maintain magnetic field	No power required to maintain magnetic field

Uses of Permanent Magnet

Various uses of Permanent magnets are discussed below.

• Powerful permanent magnets are used in the production of both hybrid and electric automobiles. The capability of the magnets to transform mechanical energy into electrical energy is the key idea at play here. These magnets, which are a crucial part of the cars, are created from materials that contain a lot of rare earth magnets.
• The permanent magnet is fastened around a moving electromagnetic coil found in loudspeakers. The loudspeaker’s vibration frequency determines the pitch or volume of the sound it produces.
• Disk drives are another practical application for permanent magnets. They are crucial in assisting with data storage in the discs. Three permanent magnets typically make up hard disc drives (HDDs).
• Both in industrial settings and backyard gardening, pumps and magnetic materials are useful. A typical centrifugal pump setup is similar to that of a magnetic drive centrifugal pump.

Advantages and Disadvantages of Permanent Magnet

Let’s look at some advantages and disadvantages of permanent magnets.

Advantages:

• Permanent magnets do maintain their magnetism for a long time compared to other magnets.
• Their polarity won’t change and they won’t get demagnetized easily.

Disadvantages:

• Only below a specific temperature can a permanent magnet produce a magnetic field. This makes these magnets unsuitable for applications involving hot devices.
• These permanent magnets degrade over time. The intensity of the maximal magnetic field decreases as a result.
• The poles of a permanent magnet cannot be altered.

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