(Easy Guide): What is a Rare Earth Magnet? - Complete Study
While we all know what magnets are, not everyone knows about the makeup of different kinds of magnets. There are common everyday magnets, which is probably what you have laying around the house, as well as larger-scale magnets being used by NASA, all of which have their own unique types and characteristics.
What is a Rare Earth Magnet? Rare earth magnets are extremely strong, permanent magnets that are made from rare earth elements like samarium cobalt and neodymium. They are one of the strongest type of magnets made, and have opened doors within industrial magnet use.
There are seventeen elements that are considered rare earth elements on the periodic table, which are also sometimes called rare earth metals. These elements are the fifteen lanthanide elements, as well as two transition metals (scandium and yttrium).
While your average person doesn’t often have a use for rare earth magnets, they aren’t inhibitive to buy for something like a special craft project. They often are used in jewelry making to create extremely strong clasps, or sometimes in housewares like magnetic key holders.
What is a Rare Earth Magnet?
While a rare earth magnet could technically be made from any of the seventeen rare earth elements, they are usually made out of samarium cobalt and neodymium.
To be specific, these elements are light rare earth elements, also known as LREE, and are considered part of the cerium earths group.
Magnets made from these two elements are considered some of the most powerful magnets we can make, and are often used in industrial and commercial applications.
Scandium, because it is often found in rare earth element deposits, is often also labelled as a rare earth element.
These powerful magnets tend to be shockingly compact. Extremely small versions of these magnets, as small or smaller than your pinky nail, are often marketed as very strong fridge magnets.
These can hold quite a few more bills than your average magnet, without taking up any space!
Though we continue to call them ‘rare’ earth magnets, the elements used to make them are not actually that hard to find.
Almost all of these metals are considerably less rare than gold. A better comparison might be to something like lead, which as we know if quite widespread and common.
What makes gathering these resources ‘rare’ is that it is hard to find some of them in concentrations that are considered worth it to mine.
Often, especially with neodymium, you will find such little amounts that potential miners will completely pass over the area. This has to do with the fact that they are not often found in veins, they are scattered throughout an area unevenly, which makes it much harder to collect.
These elements are also often found together in the same mineral deposits mixed together. Currently China refines and mines the most rare earth element, but the United States, Japan, and Australia are also known to process them.
Due to export restrictions from China, there has been a resurgence in research programs on strong magnets that do not use rare earth metals.
Rare earth magnets were first developed in the 1960s, when two workers in the US Air Force Materials Laboratory, J. Strnat and G. Hoffer realized that an alloy combining cobalt and yttrium was extremely magnetic in comparison to other materials of the time.
Though we no longer use yttrium as a main rare earth magnet resource, the discovery helped open the doors to these types of magnets.
Rare earth elements have many applications, such as within the electronics industry, the medical industry, the military, the aerospace industry, and the automotive industry. The applications we use these rare earth magnets ranges from household items to MRI machines.
Wind turbines, for example, sometimes require two whole tons of rare earth magnets, which helps the turbines be extremely efficient. They also are used in items like hard disk drives and as previously mentioned, jewelry clasps.
A more recent use for rare earth magnets are toys. Like legos, they are strong enough to create structures and patterns out of. These toys have been extremely popular, but are usually only meant for older children or adults due to the small size of the magnets used in them.
Some Uses for Rare Earth Magnets:
- Wind turbines
- Electronics (hard disk drives, speakers, headphones)
- MRI machines
- Anti-lock breaking sensors
- Space exploration rovers
- Electric car batteries
- Energy-efficient lighting
- Cell phones
A cool note is that, when you set your phone to vibrate mode, the buzz is caused by a small neodymium magnet that is within your phone!
That noise you hear makes more sense when you know that the magnets within headphones and speakers is what allows for the impressive bass range.
Another cool technological use for these magnets is television sets. New models of televisions use neodymium magnets in order to redirect electrons to the screen, which allows for a much better image quality.
One of the large advantages of rare earth magnets is that they are ‘permanent’ magnets, which means what once they are given a charge, they should continue to hold that charge for years and years.
If they are damaged, that will still cause them to potentially lose this charge. Ceramic magnets are the other popular form of permanent magnet, though they are not nearly as powerful as rare earth magnets. They do have some uses, and we will cover that later.
There are hazards that are important to note when working with extremely strong magnets. Larger magnets are strong enough to cause potential injury if skin and body parts get pinched between magnets or magnets and metal.
This can be severe enough to even harm bones. When swallowed, magnets can cause internal harm, though this is usually only a concern if children will be able to access the magnets. Also, if a magnet is hit too hard, potentially by another magnet, they can break and cause chips to fly at high velocity.
Also, the toxicity of neodymium is low-to-moderately acute. It is important to handle it carefully, and to avoid any unnecessary contact with it.
There are ways to prevent this from being an issue, such as certain plating. With all that being said, it is not a significant risk since they should not be ingested.
Types of Rare Earth Magnets
There are two main types of rare earth magnets, samarium cobalt magnets and neodymium magnets. While it may seem like these two magnets should be similar as they are both rare earth elements, they are actually very different.
|Samarium Cobalt Magnets:||Neodymium Magnets:|
|Strong magnetic field for their size (but not as strong)||Stronger magnetic field than Samarium Cobalt|
|Better at handling high temperatures||Lower temperature tolerance|
|Higher in price (more market sensitive)||Lower in price|
|Brittle and prone to cracking/chipping if incorrectly used||More susceptible to corrosion (unless specially treated)|
Neodymium magnets were made by General Motors as well as Sumitomo Specialty Metals in order to combat the costs of samarium cobalt magnets in the 1980s.
Since then, neodymium magnets have become much more popular overall, but are still cheaper! The name also comes from the Greek term neos didumous, which translates to “new twin.”
Samarium cobalt magnets were the first rare earth magnet type ever invented. They have a weaker magnetic field than neodymium, but a higher Curie temperature.
A higher Curie temperature means that they are able to be used at higher temperatures without risking the magnetism. This makes them more useful for high temperature environments, like in some technological hardware. It can function at temperatures up to 662 degrees Fahrenheit.
They also have a very high resistance to oxidation, but also are more brittle. Because they are more susceptible to cracking, engineers have to be much more careful when using samarium cobalt magnets.
It is important to take care when using these types of magnets to not put them within items that could be easily dropped or that will have repeated impact.
Neodymium magnets have the highest magnetic energy density of all magnetic materials. Because of this, a pretty small amount of it can be used in comparison to other magnets.
This helps make it much more affordable. It is because of this combination of relative strength to size and price that they are a popular pick for jewelry and home goods.
An interesting note is that neodymium is also used in laser technology, and radiation filtering. It really is a versatile element!
These magnets are made from an alloy consisting of neodymium, iron, and boron. These additions can help strengthen the element, which normally has an inhibiting low temperature tolerance.
Neodymium magnets have the highest magnetic field strength and stability, but they have a much lower Curie temperature as we have said and are more likely to suffer from oxidation and rusting.
There are treatments to prevent this, however it adds cost to the magnet which may be the whole appeal for the purchaser in the first place.
There is a treatment that has been used by NASA for neodymium magnets that allows them to work at higher temperatures.
Something called grain boundary diffusion technology enables the element dysprosium is added to neodymium, iron and boron to allow it to work at much higher temperatures than it normally would.
It goes without saying that these magnets are constantly being worked on, and more powerful versions of the magnets are being researched constantly.
There is a large push currently to improve upon the accessibility of rare earth magnets due to their role in green and renewable energy. They are also used in hybrid and electric cars often in order to power their special DC motors.
It has been said that samarium cobalt magnets may be part of the key to future technology like cryogenic tech and the very high operating temperature technology that would be used for future aerospace systems.
While future speculation is very interesting, it is also entirely possible we will have discovered a better source for magnets by then!
Rare Earth Magnets Vs Ceramic Magnets
Ceramic magnets have been around since the 1950s. The process for making ceramic magnets is actually quite similar to the process of making ceramic kitchenware.
They are probably the magnets you are familiar with from when you were younger, and have been commonly used around the house for longer than rare earth magnets.
These magnets are made of strontium or barium elements as well as iron oxide. They have also been called ‘hard ferrite’ magnets when referring to the permanent version.
There are also ‘soft ferrite’ magnets, which are not permanent and often used in transformers, and ‘semi-hard ferrite’ which is often used for sensors or actuators.
Ceramic magnets are much less powerful than rare earth magnets, sometimes being around ten times weaker. They also are quite brittle. Though that may make them seem like they are the weaker choice of the two, they actually have quite a few benefits.
Unlike neodymium magnets, ceramic magnets are quite resistant to corrosion, and often don’t need extra coatings of protectant.
This means not only are they cheaper, but you also don’t have to factor in the additional costs to keep them lasting for a long time. Ceramic magnets are very easy to magnetize, but also are resistant to demagnetization by any outside fields. They also are significantly less expensive.
Rare earth magnets, as we have mentioned, are the most powerful of all permanent magnets.
Though they are sometimes more susceptible to oxidization and corrosion, they are also extremely resistant to demagnetization by external fields just like ceramic magnets.
While ceramic magnets have a better temperature tolerance than neodymium magnets, samarium cobalt has quite a bit higher temperature tolerance than ceramic.
Ceramic Magnet Pros and Cons:
|+ Much cheaper to produce||- Less powerful than rare earth magnets|
|+ Resistant to corrosion and demagnetization||- Can be brittle|
Overall, while rare earth magnets are better in most industrial applications, ceramic magnets are a great option for more casual household items.
The average consumer probably won’t need the power that a neodymium magnet would provide, and will appreciate the lower price point. Due to their lack of power, however, rare earth metal magnets will be a better choice in any heavier application.
Ceramic magnets are actually a great option for audio devices. They are the most common kind of magnet used in things like loudspeakers.
They also are great for house items like refrigerator magnets, and are even commonly used in small motors despite how brittle they are.
How Strong Are Rare Earth Magnets?
When looking at the strength of neodymium in particular, first it is important to understand grading.
Neodymium magnets are graded depending on what material they are made out of. Usually, the higher the grade, the stronger the magnet.
The grade is the number following the ‘N’, so for example N42 is stronger than N28. Currently, the most powerful rare earth magnet is graded at N55. It is important to note that the more powerful the magnet, the more brittle it will also become.
While N55 is the strongest graded rare earth magnet out there, it also is extremely hard to use as manufacturers don’t add the iron that usually is necessary to raise the operating temperature high enough for practical use.
For this reason, we will look at the strength of the average N52 magnet instead.
Approximate Pounds of Force to Pull N52 Straight Away From Steel:
- 1” by 1” by ½” thick brick – 65 lbs
- 2” by 2” by ½” thick brick – 140 lbs
- 3” by 3” by ½” thick brick – 210 lbs
- 4” by 4” by ½” thick brick – 310 lbs
For comparison, the average person can safely pull about 30% of their body weight. That means, a person that is 200 pounds could only safely pull 60 pounds of force. That is less than the 1” by 1” brick!
To be fair, safely is a very relative term – with enough prying and with leverage it would be much easier to pull it away.
Though N52 magnets are extremely strong, they aren’t necessarily used more often. The extra power often ends up being unnecessary, and since they get exponentially more expensive it often makes more sense to use a larger magnet of lower power, especially since it will end up also potentially being less brittle.
An interesting study done on rare earth magnets showed that they are strong enough to interfere with shark’s ability to sense electrical fields, and can potentially even be used to repel them!
It may be implemented on nets to prevent sharks and manta rays from getting trapped in them or attempting to bypass them.
In conclusion, rare earth magnets have their own unique characteristics that make them useful in a variety of situations and easy to spot out.
Through all of the information that was provided in this article, you should now have the answers to everything you could have ever wanted to know about rare earths!