What Is a Cobalt Magnet?
Cobalt Magnets are magnets that contain cobalt.
Most often, it refers to Samarium Cobalt Magnets. When the ferromagnetic Cobalt and the rare earth Samarium are alloyed in a composition of 1:5 or 2:17, they have the properties of a powerful magnet. Next to neodymium magnets, cobalt magnets have the strongest magnetic force and have excellent temperature characteristics, making them important magnets in industry.
Uses of Cobalt Magnets
Cobalt Magnets are superior to Neodymium Magnets in terms of temperature characteristics. Since its magnetic force does not decrease even at high temperatures, it is suitable for applications requiring temperature stability. On the other hand, they are fragile and easily broken, so care must be taken when using them in applications where strength is required.
The following are examples of applications of Cobalt Magnets:
- Electrical motors for office automation equipment.
- Industrial motors such as those used to drive electric vehicles.
- Rotary sensors.
- Medical precision parts.
- Acoustic equipment and generators.
Principle of Cobalt Magnet
Cobalt Magnet is a generic term for magnets with cobalt as the main component. It is created by alloying cobalt with other metallic elements.
Cobalt is a transition metal element with atomic number 27 and element symbol Co, and is ferromagnetic. It belongs to group 9 on the periodic table, the same group as iron, and has silvery-white color and iron-like properties. However, it is also hard and resistant to oxidation.
Types of Cobalt Magnets
Cobalt magnets are classified into two types: Alnico magnets and Samarium Cobalt magnets.
1. Samarium Cobalt Magnet
Samarium is a rare earth element with atomic number 62 and element symbol Sm. It has a grayish-white color and soft properties. Samarium itself is not ferromagnetic. When combined with cobalt to form SmCo5 (1-5 series) or Sm2CO17 (2-17 series) alloys, it becomes highly magnetic.
Because they are more thermally stable and corrosion resistant than neodymium magnets, they are used in automotive products such as magnetic sensors, actuators for smartphone cameras, and medical devices. On the other hand, its weak mechanical strength limits where it can be used.
When first developed, these magnets had a composition ratio of samarium 1 to cobalt 5. However, Dr. Yoshio Tawara, a Japanese physicist, developed a Cobalt Magnet with several transition metal elements such as iron, copper, and zirconium added in addition to samarium and cobalt. Research results have shown that this magnet has very high performance among Cobalt magnets.
An example of the composition of a samarium-cobalt magnet currently on the market is one that contains 51 wt% cobalt, 26 wt% samarium, 17 wt% iron, and 6 wt% copper. Although these magnets are superior to other magnets in terms of heat resistance, they tend to be more expensive because they contain more cobalt.
2. Alnico Magnet
Magnets made of an alloy containing aluminum, nickel, cobalt, iron, and titanium. The name comes from the initial letters of aluminum, nickel and cobalt.
It is characterized by its high magnetic susceptibility and heat resistance. It is generally used in industrial equipment such as audio equipment, motors, and generators. It is often used in high-temperature environments because its magnetic properties change with temperature.
There are several types of Alnico magnets, including Alnico 2, Alnico 5, and Alnico 8.
Alnico 2 has the strongest magnetic force of all alnico magnets and is used in pickups for audio equipment. Alnico 5 has stable magnetic force at high temperatures and is used in industrial equipment such as motors and generators. Alnico 8 has a stronger magnetic force than Alnico 5 and generates higher magnetic energy and is used in motors and generators for higher performance.
Other Information on Cobalt Magnets
Ignition of Cobalt Magnets
Cobalt Magnets can ignite under certain conditions and must be handled with care. In particular, they are easily ignited when the magnet surface is dry or cleanly polished and may burn at low temperatures.
In addition, Cobalt Magnets are easily chipped by impact, which may result in a fine powder of Cobalt alloy. Because of the risk of spontaneous combustion, this metallic powder is designated as a Class II flammable solid under the Fire Service Act. Cobalt Magnets should be used safely and avoid any usage that may cause the Cobalt Magnet to wear out and produce alloy powder.