to sustainability?

Efforts are underway to develop new magnetic materials that improve sustainability and maintain performance in industrial applications.

There are three primary magnet types — temporary, permanent, and electromagnets — each with multiple subcategories. Subcategories for permanent magnets and electromagnets include materials and designs optimized for specific characteristics and improving sustainability.

Temporary magnets

Temporary magnets are magnetic only in the presence of an external magnetic field. Materials like iron, nickel, cobalt, and many types of steel can act as temporary magnets. The field strength of temporary magnets is related to the material being used and the external magnetic field’s strength, proximity, and other characteristics. As soon as the external field is removed, temporary magnets stop being magnetic.

Characteristics of temporary magnets include:

• Easily magnetized by an external magnetic field

• Simple structures

• Low cost

• Can be used to set metals and nonmetals

Most nonmetal magnetic materials are temperature sensitive, and the strength of their magnetic field decreases at elevated temperatures. In addition, many of these materials have low corrosion resistance.

While temporary magnets are often associated with ferrous materials, paramagnetic and superparamagnetic materials can also be used for temporary magnets. Paramagnetic materials, such as alkali metals, some transition metals, aluminum, tin, and oxygen, have a weaker field strength than ferrous materials.

Superparamagnetism is paramagnetism at a very strong level, and superparamagnetic temporary magnets can be very strong, but there’s a catch. Superparamagnetism is highly size-dependent and only exists in nanocrystals. It’s a form of magnetism that appears in small ferromagnetic or ferrimagnetic nanoparticles. Like the case of a paramagnetic material, an external magnetic field can magnetize the nanoparticles in a superparamagnetic material. Still, the magnetic susceptibility — the degree of magnetization in an external magnetic field — is much larger than that of regular paramagnets.

Permanent magnets

Unlike temporary magnets that need the application of an external field to become magnetized, permanent magnetics generate their own field. Permanent magnets can retain their magnetic properties for extended periods, even multiple years, and provide the magnetic field to use temporary magnetic materials.

Permanent magnets are often divided into two groups: (1) metal alloy magnets, such as aluminum nickel cobalt and samarium cobalt magnets, and (2) neodymium iron boron and ferrite or ceramic magnets.

Ceramic or ferrite magnetic materials can be soft (easily magnetized and demagnetized) or hard (difficult to magnetize and demagnetize). Ceramic or ferrite permanent magnets are made with hard magnetic materials like barium hexaferrite (BaFe12O19) and strontium hexaferrite (SrFe12O19). Both materials are hard and brittle and represent the largest permanent magnets used today. They generate moderate remanence induction but have performance advantages in terms of resistance to demagnetization and corrosion and the absence of eddy current losses. They have good availability and are low cost. If the performance of these materials could be increased even modestly, they could take away market share from higher-performing metal alloy magnets.

Permanent magnets made with aluminum, nickel, and cobalt are called alnico magnets. They have good temperature performance but are relatively easy to demagnetize. Their overall performance and cost place them between ceramic or ferrite magnets and rare earth magnets. Alnico magnets can be fabricated using sintering or casting processes. Sintering results in mechanically more robust magnets, while casting produces higher magnetic energy levels and can support the production of magnets with more complex shapes.

Samarium cobalt (SmCo) magnets are rare earth magnets and can be made with Sm1Co5 and Sm2Co17, referred to as 1:5 and 2:17,

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