Permanent Magnet

Permanent Magnet

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A permanent magnet is a magnet that does not lose its magnet field. However what makes a magnet permanent? In order to understand this we need to know how magnets work. Magnetism is an aspect of the phenomenon known as the electromagnetic force a fundamental force of the physical universe. Magnetism like its other aspect electricity manifests itself as a field. What makes a magnet is when certain substances and elements are induced with a strong magnetic field. In the case of permanent magnets this field remains over time without weakening.

A permanent magnet is a magnet because of the orientation of its domains. Domains are the small magnetic field inherent in the crystalline structure of ferromagnetic materials. Ferromagnetic materials are the only substances capable of being made into magnets they are normally iron, nickel, or alloys that are made or rare-earth metals. A magnet is created when certain condition cause separate domains in a ferromagnetic item to be all aligned in the same direction. However the method used in most cases weak magnets can only be made. This is normally by direct contact with a naturally magnetic material or by running an electric current through it. However in the case of a field produced by rubbing it against a strong magnet is too weak and will fade over time as the domains return to their original positions.

The main way that permanent magnets are created is by heating a ferromagnetic material to a key high temperature. The temperature is specific to each kind of metal but it has the effect of aligning and “fixing” the domains of the magnet in a permanent position. It is conjectured that this same process inside the Earth is what creates natural permanent magnets.

Permanent magnets are important for their industrial uses especially when it comes to power generation and electric motors. The induction process for turbines and generators needs permanent magnets to turn mechanical motion into energy. They are also important for electric motors in many electronics using the reverse of the induction of electric current to make mechanical energy. As you can see without the permanent magnet we would not be able to take full advantage of the capabilities of electricity in modern devices.

We have written many articles about permanent magnets for Universe Today. Here’s an article about bar magnets, and here’s an article about super magnets.

If you’d like more info on permanent magnets, check out these articles from Hyperphysics and Practical Physics.

We’ve also recorded an entire episode of Astronomy Cast all about Magnetism. Listen here, Episode 42: Magnetism Everywhere.

References:
Hyperphysics
How Magnets Work

Super Magnets

Permanent Magnet

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Magnets are not only a source of endless fun – for children and children of all ages! They also happen to have endless industrial applications. But when it comes to the high-tech industry, the people who rely on magnetic materials to build appliances, electronics, or even spaceships, only one type of magnet will do. These are known as Rare Earth or Super Magnets, the kind that are used in MRI machines, computer hard drives, electric and hybrid motors, audio speakers, electric guitars, and race car engines. In spite of their name, the elements used to make super magnets are actually quite common, but were rarely found in large enough quantities to be considered economically viable. However, since the 90’s these magnets have become cheap and widely available, and are even being considered for additional processes.

The term super magnet is a broad term and encompasses several families of rare-earth magnets that include seventeen elements in the periodic table; namely scandium, yttrium, and the fifteen lanthanides. First developed in the 1970’s and 80’s, super magnets are the strongest type of permanent magnets ever made, are ferromagnetic, meaning that like iron they can be magnetized, and have Curie temperatures that are below room temperature. This means that in their pure form, their magnetism only appears at low temperatures. However, since they can form compounds with transition metals such as iron, nickel, and cobalt, metals that have Curie temperatures well above room temperature, they can be used effectively at higher temperatures as well. The main advantage they have over conventional magnets is that their greater strength allows for smaller, lighter magnets to be used, ones that can do the same job but take up less space and require less material.

Super magnets can be broken down into two categories. First, there is the neodymium magnet, which is made from an alloy of neodymium, iron, and boron to form the Nd2Fe14B tetragonal crystalline structure. This material is currently the strongest known type of permanent magnet and was developed in the 1980’s. It is typically used in the construction of head actuators in computer hard drives and has many electronic applications, such as electric motors, appliances, and magnetic resonance imaging (MRI). The second type of super magnet is the samarium-cobalt variety, an alloy of samarium and cobalt with the chemical formula of SmCo5. This second-strongest type of rare Earth magnet is also used in electronic motors, turbomachinery, and because of its high temperature range tolerance may also have many applications for space travel, such as cryogenics and heat resistant machinery.

We have written many articles about magnets for Universe Today. Here’s an article about where to buy magnets, and here’s an article about what magnets are made of.

If you’d like more info on Super Magnets, check out Rare Earth Magnetics Homepage, and here’s a link to Wikipedia: Rare Earth Magnets.

We’ve also recorded an entire episode of Astronomy Cast all about Magnetism. Listen here, Episode 42: Magnetism Everywhere.

Sources:
http://en.wikipedia.org/wiki/Rare-earth_magnet
http://en.wikipedia.org/wiki/Magnet
http://en.wikipedia.org/wiki/Samarium-cobalt_magnet
http://en.wikipedia.org/wiki/Neodymium_magnet
http://www.newton.dep.anl.gov/askasci/phy99/phy99010.htm