What are the differences between alnico and samarium - cobalt cylindrical magnets?

Hey there! As a supplier of cylindrical magnets, I get asked a lot about the differences between alnico and samarium - cobalt cylindrical magnets. So, I thought I'd break it down for you in this blog post.

Let's start with the basics. Alnico magnets are made from an alloy of aluminum (Al), nickel (Ni), and cobalt (Co), along with other elements like copper and iron. On the other hand, samarium - cobalt magnets, as the name suggests, are made from an alloy of samarium and cobalt.

Physical and Magnetic Properties

One of the most obvious differences between the two is their physical appearance. Alnico magnets are usually silver - gray in color and have a somewhat rough surface finish. They can be cast or sintered, and cast alnico magnets often have a more porous structure compared to sintered ones. Samarium - cobalt magnets, on the other hand, have a darker, more metallic - looking finish. They are typically sintered, which gives them a more uniform and dense structure.

When it comes to magnetic properties, alnico magnets have a relatively high remanence (Br), which means they can hold a strong magnetic field. This makes them great for applications where a stable magnetic field is required over a long period. However, they have a low coercivity (Hc), which means they can be demagnetized relatively easily by external magnetic fields or high temperatures.

Samarium - cobalt magnets, in contrast, have both high remanence and high coercivity. This makes them extremely resistant to demagnetization, even in harsh environments with high temperatures and strong external magnetic fields. Their high coercivity also allows them to maintain their magnetic strength in smaller sizes compared to alnico magnets.

Temperature Performance

Temperature is a crucial factor when choosing between these two types of cylindrical magnets. Alnico magnets can operate at very high temperatures, up to around 525°C (977°F). They actually have a positive temperature coefficient of remanence, which means their magnetic strength increases slightly with temperature up to a certain point. This makes them ideal for high - temperature applications such as in some types of motors and generators.

Samarium - cobalt magnets can also handle high temperatures, with an operating temperature range of up to about 350°C (662°F). Although their maximum operating temperature is lower than that of alnico magnets, they maintain their magnetic properties much better within their operating range. They have a negative temperature coefficient of remanence, but it's relatively small, so their magnetic strength doesn't drop off too significantly as the temperature increases.

Cost and Availability

Cost is always a consideration in any purchasing decision. Alnico magnets are generally less expensive than samarium - cobalt magnets. This is because the raw materials used in alnico magnets, such as aluminum, nickel, and iron, are more abundant and less costly compared to the rare - earth elements used in samarium - cobalt magnets, like samarium.

In terms of availability, alnico magnets are more readily available in the market. They have been around for a long time and are produced by many manufacturers. Samarium - cobalt magnets, while still widely available, may have more limited supply due to the scarcity of samarium and the more complex manufacturing process.

Applications

The differences in their properties lead to different applications for alnico and samarium - cobalt cylindrical magnets.

Alnico magnets are commonly used in applications where high - temperature stability and a relatively strong magnetic field are needed. For example, they are used in guitar pickups to produce a warm and rich sound. They are also used in some types of meters, sensors, and relays. You can find more information about cylindrical magnets suitable for these applications on our Cylindrical Permanent Magnet page.

Samarium - cobalt magnets are often used in high - performance applications where resistance to demagnetization is critical. They are widely used in aerospace and military applications, such as in guidance systems and aircraft engines. They are also used in high - end motors, generators, and magnetic couplings. If you're interested in the specific Cylinder Shape Magnet options for these applications, feel free to check out our page.

Another interesting application for cylindrical magnets is in the form of Hollow Cylinder Magnets. These can be used in a variety of ways, such as in magnetic bearings and some types of sensors.

Machinability

Machinability is another aspect to consider. Alnico magnets are relatively easy to machine. They can be drilled, cut, and ground using standard machining techniques. This makes it easier to customize them for specific applications. However, care must be taken during machining to avoid chipping or cracking, especially with cast alnico magnets.

Samarium - cobalt magnets are much harder and more brittle, which makes them more difficult to machine. Specialized machining techniques and tools are required, and the process is often more time - consuming and expensive.

Corrosion Resistance

Corrosion resistance is important, especially for magnets used in harsh environments. Alnico magnets have decent corrosion resistance, but they can still rust over time if not properly coated. A protective coating such as nickel - copper - nickel can be applied to improve their corrosion resistance.

Samarium - cobalt magnets have good corrosion resistance on their own. However, in extremely corrosive environments, a coating may still be recommended to further enhance their durability.

In conclusion, the choice between alnico and samarium - cobalt cylindrical magnets depends on your specific application requirements. If you need a magnet that can handle high temperatures and is relatively easy to machine, alnico might be the way to go. But if you need a magnet with high resistance to demagnetization and can tolerate a higher cost and more difficult machining, samarium - cobalt is a better option.

If you're interested in purchasing cylindrical magnets for your project, whether it's alnico or samarium - cobalt, don't hesitate to reach out. We can provide you with high - quality products and expert advice to ensure you get the right magnets for your needs.

References

• "Magnetics Handbook", Second Edition, Edited by John D. Adam
• "Permanent Magnet Materials and Their Applications" by E. C. Stoner and H. P. Wolfarth