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Magnetic Materials

McGill University_031422A
[McGill University]


- Overview

Magnetic materials are attracted to magnets and may even become magnetized. Almost all magnetic materials are metals. Common examples of magnetic metals include iron, nickel, cobalt, and steel. However, magnetism is a complex phenomenon. Not all iron or steel is magnetic. Even some nonmetals are magnetic. 

Magnetic materials underpin an international industry worth trillions of dollars each year. More than 99% of electrical energy is generated using a motor made of magnetic material that passes through at least two transformers before reaching the user. About 10% of the power generation is being lost, the largest part of which is in the magnetic core. 

The 2015 EU Ecodesign Regulation imposed efficiency limits on all new equipment and required a further 10% reduction in losses by 2021. This can only be achieved with the best commercially available electrical steel grades. These developments will also reduce electricity demand for electric vehicles, industry and households. 

The steps taken will expand the ability to optimize the role of magnetic materials in key elements such as design, end-use and end-of-life to optimize current processes and drive future innovations. 


- Types of Magnetism

To understand which metals are magnetic, it helps to review five types of magnetism: 

  • Diamagnetic: All matter is diamagnetic, which means it repells magnetic fields very weakly. In magnetic materials, the attractive force of the magnet exceeds the repulsive force of the diamagnetism.
  • Paramagnetic: Paramagnetic materials are less attractive to magnetic fields. Aluminum, oxygen, iron oxide (FeO) and titanium are all paramagnetic.
  • Ferromagnetism: Ferromagnetic materials are strongly attracted to magnets and can be magnetized. Ferromagnetic materials lose their magnetism at temperatures above the Curie point. Iron, cobalt, nickel, most of their alloys, and some rare earth metal compounds are ferromagnetic.
  • Ferrimagnetic: Ferrimagnetic materials are attracted to magnets and act as permanent magnets themselves. Above the Curie point, ferrimagnetic materials lose their external magnetism. Magnetite (magnetite, Fe3O4) has ferrimagnetism.
  • Antiferromagnetism: In antiferromagnetism, adjacent ions align at low temperatures making the material insensitive to magnetic fields. However, at temperatures above the Neel temperature, some atoms fall out of alignment and the material becomes weakly magnetic. Manganese oxide (MnO) and pure neodymium are examples of antiferromagnetic materials.

Usually, when people talk about "magnetic metals", they're talking about ferromagnetic and ferrimagnetic metals. However, more metals (and some nonmetals) are magnetic if you include conditional magnetism and weaker types of magnetism.


- Ferromagnetic Materials

Ferromagnetic materials are materials that have magnetic properties similar to iron. They can be permanently magnetized. Examples of ferromagnetic materials are nickel, cobalt, and alnico, an alnico alloy.

Ferromagnetic materials can be divided into magnetic "soft" materials, such as annealed iron, which can be magnetized but do not tend to remain magnetized, and magnetic "hard" materials, which can. 

Permanent magnets are made of "hard" ferromagnetic materials, such as Alnico and ferrite, which are specially treated in a strong magnetic field during manufacture to align their internal crystallite structure, making them very difficult to demagnetize. 


- Nonmetallic Magnetic

Nonmetals are generally considered to be nonmagnetic. Certain types of graphite (an allotrope of carbon) are highly diamagnetic and can repel strong magnets, making them appear to levitate. However, liquid oxygen and borofullerene (B80) are paramagnetic.

 Recently, scientists have developed organic magnets made of fluorographene with hydroxyl groups. These organic magnets are antiferromagnetic at room temperature.


- Magnons, Magnets and Quantum Computing

From MRI machines to computer hard drive storage, magnetism has played a role in key discoveries that have reshaped our society. In the new field of quantum computing, magnetic interactions could play a role in transferring quantum information. 

In new research (2022) at the U.S. Department of Energy's (DOE) Argonne National Laboratory, scientists have achieved efficient quantum coupling between two distant magnetic devices that can host a certain type of magnetic excitation, called for the magnon. These excitations occur when an electric current generates a magnetic field. Coupling allows magnons to exchange energy and information. This coupling may help create new quantum information technology devices. 

This instant communication does not require the sending of messages limited by the speed of light between magnons. It's similar to what physicists call quantum entanglement.  


[More to come ...]


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