In recent years, rare-earth magnets have become anything but uncommon. Not only have they begun appearing in a wide variety of industrial and consumer products, many experts have begun hailing the devices as a potential solution for environmental ills. Business-news website Quartz notes, “One high-stakes arena that could shape the trajectory of the global climate economy is the rare earth permanent magnet industry.” Market Insight Reports also states that the sector is poised for explosive expansion “with a CAGR [compound annual growth rate] of 8.5% in the forecast period of 2020 to 2025.”
In this post about rare earth magnets explained, we will describe what rare earth magnets are, their various uses and industry applications, and some of the most widely used rare earth magnets.
What Are Rare Earth Magnets?
Ironically enough, the components that comprise rare earth magnets aren’t (strictly speaking) rare. As the BBC explains, “‘Rare earths’ are a group of 17 chemically similar elements crucial to the manufacture of many hi-tech products. Despite their name, most are abundant in nature but are hazardous to extract.” Rare earths include elements such as:
While some of these elements appear in nature only rarely, others appear in abundance throughout the earth’s crust. The reason for their “rare” moniker owes to the fact that they do not often appear in easy-to-mine concentrations. Rare earth magnet mining often involves using environmentally dangerous chemicals and finding deposits that don’t require their use has proved challenging for the industry.
Rare earth magnets derive much of their power and longevity from two of the above-mentioned rare earths. (We’ll discuss that in more detail in the following section.) Part of what makes rare earth magnets special is their exceptional strength, which allow for much more magnetism in a smaller form factor. (Think of tiny rare earth magnets discs.) They also do a better job of keeping their magnetic charge. Heat, poor storage, and physical trauma can all cause traditional magnets to demagnetize.
Rare Earth Magnet Types
Rare earth magnets break down into two categories: neodymium magnets and samarium-cobalt magnets. Both types have applications in numerous industries, including power generation, audio equipment, computer equipment, medical equipment, and more. You can even find rare earth magnets in electric motors and rare earth magnets on oil filters to help prevent engine wear. Before we discuss these magnets in more depth, let’s talk about some general characteristics of these two kinds of rare earth magnets.
Rare Earth Features & Characteristics
As you can tell from the name of one of the magnets that we mentioned above, rare earth magnets aren’t entirely comprised of rare earth elements. For instance, samarium-cobalt magnets are comprised of (appropriately enough) both samarium and cobalt, while neodymium magnets contain substantial amounts of boron and iron in addition to its titular element.
Both types of magnet are extremely strong. However, neodymium boasts the strongest magnetic force. Samarium excels in its stability, resisting potentially damaging external factors such as extreme heat and corrosion.
Disadvantages of Each Type of Rare Earth Magnet
Despite their advantages, both types of rare earth magnets have significant drawbacks that end users must consider. Samarium-cobalt magnets are expensive, often prohibitively so depending on the application, and don’t have the same strength of neodymium magnets. However, neodymium has more physical disadvantages. It’s extremely susceptible to corrosion, must be coated with resistant materials, and those materials must be maintained to prevent degradation. Additionally, both types of magnets are so strong that they can lead to accidental injuries. Body parts sandwiched between rare earth magnets can get crushed, and magnets placed near one another are strong enough to fly into each other and shatter, sending dangerous, brittle shards flying everywhere.
Rare earth magnets have appeared in the news in recent years due to several injuries attributed to magnet-powered toys. These magnets are powerful, and if accidentally ingested, they can lead to serious complications. But what are rare earth magnets used for other than children’s playthings? You might be surprised to learn that rare earth magnets play a major part in many industrial products and capital assets. These include:
- Magnetic bearings and couplings
- Automatic door locks
- Jet engines
- Smart bombs
- Welding clamps
- Electric-based musical instruments
- Stud finders for construction
- Audio speakers and headphones
- Missile guidance systems
- Information-technology storage
- Radar arrays
- Generators for wind power
- Electronic countermeasures
- Satellite communications
- Magnetic resonance imaging
- Roller coasters
- Motors and starters for electric vehicles
For most applications, neodymium magnets have become the default option. In addition to being more powerful than older types of rare earth magnets, they’re significantly cheaper and less brittle. They can also be molded into a wide variety of shapes, which is another factor that has boosted their popularity. However, some of the inherent characteristics of neodymium also limit the magnets’ end uses.
Attributes of Rare Earth Neodymium
While neodymium is less brittle than samarium, it’s hardly a resilient material. Neodymium magnets are susceptible to shattering if not handled carefully. Additionally, they can quickly corrode if exposed to the air. That’s why all neodymium magnets need to be treated with a coating of nickel, zinc, tin, silver, gold, or some such similar metal. And while many classify neodymium magnets as “permanent” magnets, they can lose their magnetic properties if exposed to high heat.
Common Applications of Rare Earth Neodymium
Neodymium magnets have the widest adoption rate of any magnet in the industry. Uses include linear actuators, charged particle beam guidance, particle accelerators, disc drives, DC motors for automobiles, vacuum deposition, and microphone assemblies.
Samarium magnets were initially discovered in 1966, and while they were the world’s strongest magnets for nearly two decades, they’ve fallen somewhat out of favor since the introduction of neodymium magnets. Their brittleness, higher cost, and weaker magnetism limit their attractiveness for many applications. Still, samarium magnets can aid in unique tasks due to the element’s characteristics.
Attributes of Rare Earth Samarium Cobalt
One of the most attractive features of samarium-cobalt magnets is that they’ll retain their magnetism even under high or low heat conditions. Indeed, they’ll continue to function up to 525°F and at −459.67°F. Additionally, these magnets don’t require coating since samarium resists corrosion.
Common Applications of Rare Earth Samarium Cobalt
Samarium cobalt magnets will function in virtually every application that a neodymium magnet will. That being said, they won’t react with the same force. However, samarium cobalt magnets will excel in applications where there’s substantial humidity, high heat, or the magnet absolutely must continue functioning.
Rare-Earth Magnets and Pumps
Rare earth magnets play an important role in the fabrication of industrial pumps, particularly in oilfield applications. Application engineer Wenhuan Tang explained how so-called permanent magnets help with electrical submersible pumps (ESPs), noting, “Both neodymium iron boron and samarium cobalt magnets are the family member of rare earth permanent magnets. Depending on ESP’s application environments, different types of rare earth permanent magnets will be used. Neodymium iron boron, whose maximum operating temperature is 180°C, is normally an economical choice. Generally, NdFeB magnets need surface treatment such as NiCuNi/epoxy/Ni coating to protect it from corrosion or oxidation. On the other hand, samarium cobalt demonstrates higher temperature tolerance up to 300°C, and good corrosion resistance due to its own material properties.”
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