[Physics Class Notes] on Rare Earth Magnets Pdf for Exam

Strong permanent magnets made up of alloys of rare earth elements are known as rare earth magnets. It was developed in the 1970s and 1980s, rare earth magnets are permanent magnets and are the strongest type of magnets, producing stronger magnetic fields compared to other types of magnets like alnico or ferrite types of magnets. The rare earths magnetic fields can exceed 1.4 tesla, where ceramic or ferrite magnets exhibit magnetic fields of 0.5 to 1 tesla. 

There are two categories of earth magnets: samarium cobalt magnets and the neodymium magnets. These rare earth magnets are vulnerable to corrosion and brittle in nature.

Earth Magnets

We are well aware of the magnets and their attractive and repulsive properties. Same is the case with our planet earth. Earth also acts like a magnet. But it’s a kind of weak magnet, that’s why when we look at a compass it always points towards the north direction. Electric current in the liquid outer core mostly forms earth’s magnetic effects, which consists of conductive molten iron. Liquid ions which form a loop of current create magnetic fields. From afar, the earth looks like a magnet with it’s both the poles south and north acting as a magnet. The pole located in northern canada acts as the magnetic south pole. 

We describe the magnet’s strength in two ways: one, the force which it takes to remove the other magnets or from a steel plate. And another by the strength of the magnetic field around it. Earth magnetism has a field strength of 8000 gauss near the poles. The pull force is around 6.5Ib. Magnetic field strength of earth near the poles is 0.6 gauss, which is considered as very weak. We can use a magnet or magnetise object to be like a compass, standing on the earth’s surface. A great way to tell the direction from thousands of years is measuring the direction of the magnetic field.

Types of Rare Earth Magnets

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Rare earth magnets are divided into two broad categories of magnets that are: samarium cobalt magnets and neodymium magnets. 

Samarium Cobalt Magnet: SmCo5 is its chemical formula.  They have high cost and low magnetic field that’s why they are used less as compared to neodymium magnets, though they are known as the inventor of this family.however, the curies temperature of samarium cobalt magnet is high, that creates a niche for these magnets in application where high field strength needs high temperature. They are resistant to oxidation but the cobalt magnets are prone to chipping as they are brutile.

Neodymium Magnets: they were invented in the 1980s, they are the most affordable and rare types of magnets. They are made up of iron, bronze and alloy of neodymium. 

These magnets are used in many applications where strength is required. They have higher coercivity and higher strength as well. 

The high cost of the magnets depends on their usage and application of the magnets.

How Are Rare Earth Magnets Made

The most powerful method of forming magnets is known as power meteorology though there are many ways we do it. In this process the suitable composition is pulverised. That’s why these magnets are called sintered magnets. Under vacuum or inert gas type suitable raw materials are melted, the molten alloy is processed in a strip caster- a device that forms it thin or poured into a mould, ontu a plate.the chunks are purlized and crushed to form a fine powder, which ranges 3 to 7 microns in diameter.

This powder is chemically reactive and is capable of spontaneous igniting in the air itself. And is therefore protected from oxygen. Another metal involves aligning of particles so that all the magnetic regions in the finished part are pointing in the prescribed direction. One of the methods is called transverse or axial pressing. In the axil method powder is placed in a cavity while in the transverse method pressing of material is done with a particular temperature. 

Uses of Rare Earth Magnet

Their prices were becoming competitive in the 1990s so the neodymium is being replaced by ferrite and alnico in their application methodology as it is a powerful magnet. The smaller and lighter magnets are used for many applications as they are powerful. Some of their common applications includes: computer hard disk drives, they are used in wind turbine generators, headphones and speakers, bicycle dynamos, MRI scanners, fishing reel breakers, in cordless tools in permanent magnet motor, high performance AC servo motors, integrated starter generator in hybrid and electric vehicles and transaction motors, mechanical power flashing, maintaining product priority in the industrial field, in lubricating oil capture of the fine metallic particles. Some of the other applications of rare earth magnet are :  linear motors, slow or stop motion animation, diamagnetic levitation which is used in studying superconducting levitation   and in electrodynamic bearing, LED throwies, they are also used in preparing magnetic toys, they are also used in preparing miniature magnetic figures.