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Which Metals Are Magnetic

Neodymium Magnets 02/24/2020

Which Metals Are Magnetic?

Which Metals Are Magnetic

Common examples are Alnico alloy, an iron alloy with aluminum, nickel and cobalt. Alnico alloys make strong permanent magnets. Ferrite, a ceramic compound composed of iron oxide and other metallic elements. Ferrites are used in refrigerator magnets and small electric motors.

Magnets were first discovered by ancient civilizations going back 2,500 years, and by the 12th and 13th centuries AD, magnetic compasses were commonly used for navigation in China and Europe.

Today, magnets are an essential part of modern technology.

They are found in almost any appliance you can name, from mobile phone speakers to electric motors, washing machines and air conditioners.

The magnet industry continues to grow due to the increased demand for magnetic circuit components widely used in industrial equipment, while technological advances enable magnets to be 60 times as strong as they were 90 years ago.

Which Metals Are Magnetic?

Some alloys of rare earth metals

These magnetic metals fall under the categories:

Permanent Magnets

Neodymium Magnets

Permanent Magnets

When people think of magnets, they’re often thinking of permanent magnets.

These are objects which can be magnetized to create a magnetic field.

The most common example is the refrigerator magnet, used to hold notes on our refrigerator door.

The most common metals used for permanent magnets are iron, nickel, cobalt and some alloys of rare earth metals.

There are two types of permanent magnets: those from “hard” magnetic materials and those from “soft” magnetic materials. “Hard” magnetic metals tend to stay magnetized over a long period.

Common examples are:

Alnico alloy, an iron alloy with aluminum , nickel and cobalt.

Alnico alloys make strong permanent magnets.

They are widely used in industrial and consumer electronics.

For example, in large electric motors, microphones, loudspeakers, electric guitar pickups and microwaves.

Ferrite, a ceramic compound composed of iron oxide and other metallic elements.

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Ferrites are used in refrigerator magnets and small electric motors.

“Soft” magnetic metals can be magnetized but lose their magnetism quickly.

Common examples are iron-silicon alloys and nickel-iron alloys.

These materials are typically used in electronics, for example transformers and magnetic shielding.

Electromagnets

Electromagnets are made from a coil of copper wire wound around a core made from iron, nickel or cobalt.

The coiled wire will generate a magnetic field when an electric current passes through it, however, the magnetic field disappears the moment the current stops.

Electromagnets need electricity to work.

Their usefulness lies in the ability to vary the strength of the magnetic field through controlling the electrical current in the wire.

Electromagnets are commonly used in electric motors and generators.

They both work on the scientific principle of electromagnetic induction, discovered by scientist Michael Faraday in 1831, which says that a moving electric current will create a magnetic field, and vice versa.

In electric motors, the electric current generates a magnetic field which moves the motor.

In generators, an external force such as wind, flowing water or steam rotates a shaft which moves a set of magnets around a coiled wire, thus producing an electric current.

Electromagnets are also used to flick the switches in relays, used in telephone exchanges, railway signaling and traffic lights.

Junkyard cranes are also fitted with electromagnets which are used to pick up and drop large vehicles with ease.

These electromagnets take the form of a round plate fitted to the end of the crane.

A modern train system known as Maglev (short for magnetic levitation) uses electromagnets to levitate the train above the rail.

This reduces friction and allows the train to move at tremendous speed.

Advanced applications of electromagnets include magnetic resonance imaging (MRI) machines, and particle accelerators (like the Large Hadron Collider).

Neodymium Magnets

Neodymium magnets are a type of rare-earth magnet comprised of an alloy of neodymium, iron and boron.

They were devised in 1982 by General Motors and Sumitomo Special Metals.

Neodymium magnets are the strongest type of permanent magnet commercially available.

They are used when strong permanent magnets are required, particularly in cordless tool motors, hard disk drives and magnetic fasteners.

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Turning Non-Magnetic Metals Into Magnets

Copper and manganese are not normally magnetic.

However, a ground-breaking new technique, developed by Oscar Cespedes of the University of Leeds, UK, has transformed copper and manganese into magnets.

Cespedes and his team fabricated films of copper and manganese on carbon structures called Buckyballs.

When an external magnetic field was applied and removed, the films retained 10% of the magnetic field.

This new technique is set to provide a more biocompatible and environmentally-friendly way to manufacture MRI machines.

Other possible applications include use in wind turbines.

Wind turbines currently use iron cobalt and nickel with rare-Earth elements.

But these elements are expensive and tough to mine.

The breakthrough opens the possibilities to cheaper alternatives.

Metal Supermarkets

Metal Supermarkets is the world’s largest small-quantity metal supplier with over 85 brick-and-mortar stores across the US, Canada, and United Kingdom.

We are metal experts and have been providing quality customer service and products since 1985.

At Metal Supermarkets, we supply a wide range of metals for a variety of applications.

Our stock includes: stainless steel , alloy steel , galvanized steel , tool steel , aluminum , brass , bronze and copper .

Our hot rolled and cold rolled steel is available in a wide range of shapes including: bars, tubes, sheets and plates.

We can cut metal to your exact specifications.

Notes on Classification of Magnetic Material

There are three types of magnetic materials.

They are:

Diamagnetic material

Ferromagnetic material

Diamagnetic material

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Those substances which are feebly magnetized in the direction opposite to the applied field are called diamagnetic material.

Examples of diamagnetic materials are bismuth, copper, water, mercury, alcohol, argon, gold, tin, mercury, antimony, etc.

The magnetic moment of atoms of a diamagnetic material is zero.

They acquire induced dipole moments when the material placed in an external magnetic field.

These moments are opposite in the direction of the applied field.

The diamagnetic materials are repelled by magnets.

When a diamagnetic liquid in a watch glass is placed over two closely spaced pole pieces of the magnet, it is depressed at the middle while in the case of pole pieces separated by a distance, it rises in the middle.

Similarly, when a diamagnetic liquid is placed in a U-tube and one of the limbs of the tube is placed between the two strong pole pieces of magnet, the liquid depressed at that limb.

The diamagnetic materials move from a stronger to a weaker field.

A diamagnetic rod, freely suspended in a magnetic field, slowly turns to set at the right angle to the applied field.

Since magnetization is opposite in direction to an applied field, the diamagnetic materials have a small value for the intensity of magnetization, I.

The materials have always negative magnetic susceptibility, \(\chi = (\mu_r -1)\) and accounts from -10-6 to -10-5.

These materials are independent of temperature.

Paramagnetic Material

Those materials which are weekly magnetized in the same direction of the applied magnetic field are called paramagnetic material.

The examples of paramagnetic materials are aluminum, chromium, oxygen, manganese, alkali, alkaline earth metal, etc.

The paramagnetic materials have permanent magnetic moments.

These moments interact weekly with each other and randomly orient in a different direction.

The paramagnetic materials are feebly attracted by magnets.

A paramagnetic rod, freely suspended in a magnetic field, aligns along the field.

The paramagnetic materials are temperature dependent and follow curve law.

The relative permeability is nearly unity than ranges from 1.00001 to 1.003 for common ferromagnetic materials at room temperature.

So, the magnetic lines of force inside the material placed in a magnetic field are more than that outside it.

The susceptibility of paramagnetic substances has a small positive value.

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Ferromagnetic Material

The ferromagnetic materials are highly magnetized in a magnetic field.

The examples of ferromagnetic materials are iron, nickel and cobalt, and their alloys such as alnico.

Gadolinium and dysprosium are ferromagnetic at low temperatures.

Ferromagnetic materials are highly attracted by magnets.

Ferromagnetic materials more from weaker to stronger fields.

A ferromagnetic rod, freely suspended in a magnetic field, turns fast to set along the applied field.

The magnetic susceptibility is positive and very high and varies with the applied field.

The relative permeability is very high in the order of 1000 to 100,000.

Ferromagnetic dust in a watch glass, placed over two closely spaced pole-pieces of the magnet, increases in the middle, while pole piece is separated by a distance, depresses in the middle.

Domain Theory of Ferro Magnetism

Fig: Magnetic domain in ferromagnetic material

Each atom of ferromagnetic substance has a permanent magnetic substance;

in the unmagnetized state, the atomic and molecular dipoles are arranged randomly so the net magnetic moment is zero.

There is a strong interaction with neighboring atoms which keeps their magnetic moment aligned parallel in small regions even in the absence of an external field.

These small regions with the volume ranging between 10-12 to 10-8 m3 are called domains.

When the material is placed in an external field Be, the domains tend to orient themselves parallel to field B0.

As the applied field becomes stronger, the domains, having magnetic moments not aligned with the field, become very small and when the domains fully align to the applied field, the material attains magnetic saturation.

On removing the field, the domain walls do not move completely into previous positions.

This means material retains a magnetization in the direction of the applied field.

Fig: Hysteresis loop of ferromagnetic material

Fig: (a) Hysteresis loop of steel (b) Hysteresis loop of soft iron

Assume a piece of magnetized iron placed in a magnetizing field H.

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When the value of H is gradually increased from zero value.

The magnetic induction B in iron also increases.

When H is increased, B also increases till saturation point P but beyond P if H is increased B remains constant.

When the value of H is now decreased, B does not retrace the path PO but at the lower rate and at H being zero, B is not zero but has the finite value represented by OC.

The value of B at this point is called retentivity.

Further, when H is increased in the opposite direction, the value B falls to zero for the magnetizing field to be equal to OD.

This value of the magnetizing field is called the coercivity of the material of the specimen.

Those substances which are feebly magnetized in the direction opposite to the applied field are called diamagnetic material.

Those materials which are weekly magnetized in the same direction of the applied magnetic field are called paramagnetic material.

The ferromagnetic materials are highly magnetized in the magnetic field.

The examples of ferromagnetic materials are iron, nickel and cobalt, and their alloys such as alnico.

These small regions with the volume ranging between 10-12 to 10-8 m3 are called domains.

Magnetic Substances: Types & Examples

Everyone has played with magnets, but not everyone understands how they work.

This lesson will explain how magnets work and will take a closer look at how three different types of substances--ferromagnetic, paramagnetic, and diamagnetic--react to magnetic fields.

Background on Magnets

Magnets probably play a bigger role in your life than you think.

Sure, you see magnets on your refrigerator, but did you know that the speakers in your TV, your car's automatic door locks, and your washing machine contain magnets? In fact, even the earth is a magnet! Of course, you probably have a general idea of what a magnet is, but have you actually thought about how a magnet works, or why some materials are magnetic and others are not? If not, don't worry, you've come to the right place!

A good start would be to define some words associated with magnets.

Magnetism is the result of attraction, when two objects come together, or repulsion when two objects move apart.

A magnet is an object that has properties of magnetism.

For example, a magnet might attract another object.

A magnetic field is an invisible area around a magnet where magnetism occurs.

And magnetized means that an object acquired magnetic properties.

colorful disc plastic rubber coated neodymium magnets

Now, some substances can be super magnetic and others can be partially magnetic.

Let's take a look at three different types of substances: ferromagnetic, paramagnetic, and diamagnetic.

Ferromagnetic Substances

Let's start with ferromagnetic substances.

Ferromagnetic substances get their name because the word for iron in Latin is 'Ferrum' and iron is one of the ferromagnetic substances.

Other substances that fall into this group include cobalt, nickel, and gadolinium.

So, what makes something 'ferromagnetic?'

Everything around you, from your dog to your TV, is made up of atoms.

In the center or nucleus, of the atom, are protons and neutrons, while electrons are spinning around outside of the nucleus.

The electrons are outside of the nucleus

You can think of electrons as tiny spinning magnets.

Normally, one electron spins one way and another spins the other way, canceling each other out so the atom doesn't have any magnetic properties.

But in a ferromagnetic substance, the electrons will orient themselves to spin the same way when they are exposed to a magnetic field, thus magnetizing the ferromagnetic substance.

Check out the images below:

The electron orientation is represented by arrows.

The electrons all orient in the same way after the material is exposed to a magnetic field

You'll see that the electron orientation is represented by arrows.

The electrons all orient in the same way after the material is exposed to a magnetic field.

Picture some iron that gets placed next to a bar magnet.

The magnetic field in the bar magnet causes the electrons in the iron to orient themselves the same way and thus, makes the iron magnetic!

And what's even cooler is that ferromagnetic substances, like that chunk of iron, will remain magnetized even after that bar magnet is long gone.

Paramagnetic Substances

Paramagnetic substances are still pretty neat, even if they don't stay magnetized like the ferromagnetic substances.

They are only magnetized briefly when exposed to a magnetic substance.

Some examples of paramagnetic substances include aluminum, platinum, titanium, and tin.

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