Advances in materials science seem never ending. There are various factors to be considered when choosing a permanent magnet material for your applications. Factors such as operating temperature, demagnetising effects, energy requirements, cost limitations, environmental characteristics and available space all need to be taken into account; and to the magnetics novice, the decisions can seem overwhelming. One important consideration is that while material is key, the utilization of an optimised design is of primary importance. There are 4 major families of permanent magnetic materials commercially available. They range from hard ferrite (ceramic), which is cheap and low energy, alnico, samarium-cobalt (SmCo), to neodymium-iron-boron (NdFeB), which is expensive and high energy. Each family of materials has several grades with a range of magnetic properties. Today, application fields of these permanent magnets are extended to new industrial fields, such as electronic clocks, speakers, relays, motors, printers, communications equipment, MRI, MagLev trains, etc.

FERRITE magnets, sometimes referred to as ceramic magnets because of their product process, are the least expensive class of permanent magnetic materials. It became commercially available in the mid 1950s, and has since found its way into countless applications including are shaped magnets for motors, magnetic chucks, and magnetic tools. The raw material, iron oxide, for these magnets is mixed with either strontium or barium and milled with a ceramic binder and magnets are produced through a compression or extrusion moulding technique that is followed by a sintering process. The nature of the manufacturing process results in a product that frequently contains imperfections such as cracks, porosity, chips, etc. Fortunately, these imperfections rarely interfere with magnet performance. To enhance a ceramic magnet's performance, the ferrite compound may be biased by a magnetic field using the pressing process. This biasing induces a preferred direction of magnetization within the magnet, significantly reducing its performance in any other orientation. Consequently, ceramic magnets are available in both orientated (anisotropic) and non-orientated (isotropic) grades. Ceramic magnets are inherently brittle, and it is highly recommended that they not be utilized as structural elements in any application. The dimensional repeatability of as pressed components is difficult to control, consequently, components requiring tight tolerances necessitate secondary grinding operations to assure conformity.

ALNICO was developed in the early 1930s. During World War II it was used in military electronic applications. After the war it quickly spread into civilian versions of these applications and replaced magnet steel in many applications. High induction levels, with good resistance to demagnetisation and stability due to its low temperature coefficient, at a reasonable cost made Alnico the material of choice. A high working temperature limit (550 degrees Celsius) makes Alnico especially well suited for sensitive automotive and aircraft sensor applications. Other popular Alnico applications include: instruments, security sensors, magnetos, electronic distributors, separators, electron tubes, travelling wave tubes, radar, holding magnets, coin acceptors, generators and motors, clutches and brakes, relays, controls, receivers, telephones, microphones, bell ringers, guitar pickups, loudspeakers, security systems, and cow magnets. Alnico is made by alloying aluminium, nickel and cobalt with iron. Some grades also contain copper and/or titanium. The alloying process is casting or sintering. These constituents, the process and the heat treatment needed to optimise magnetic properties produce hard and brittle parts that are best shaped or finished by abrasive grinding. Case parts are generally under 70 pounds and may be used as is, but polar surfaces are usually ground flat and parallel. Sintering is confined to high volume parts in sizes under one cubic inch and an effective press length to diameter ratio under four.

Samarium Cobalt (Sm-Co) is the first commercially viable rare earth permanent and is considered to still be the premium material for many high performance applications. Formulated in the 1960s, it came as a revolutionary product, initially tripling the general product of other materials available at the time. Sm-Co materials come in energy products from 16 MGOe up to 33 MGOe. Their high resistance to demagnetising influences and excellent thermal stability has ensured Sm-Co as the premium choice for the most demanding motor applications. In addition, the corrosion resistance is significantly higher than, for example, NdFeB. Its corrosion resistance has also offered a high degree of comfort to those looking to use magnets in medical applications. On a "per pound" basis, Sm-Co is the most expensive permanent magnetic material. However, because of its high energy product, it has achieved considerable commercial success by decreasing the required volume of magnet material to fulfil a certain task. Sm-Co can typically be used up to 300 degrees Celsius, though, of course, its actual performance at that temperature is governed strongly by the design of the magnetic circuit. The approximately linear demagnetisation curve of Sm-CO materials allows repeatable performance over a wide range of operating conditions. As with all permanent magnets, extreme caution must be exercised when handling magnetized samples. Sm-Co can be prone to chipping and should not be used as structural components in an assembly.

Sintered NEODYMIUM-IRON-BORON (NdFeB) magnets are the most powerful commercialised permanent magnets available today, with maximum energy product ranging from 26 MGOe to 52 MGOe. NdFeB is the third generation of permanent magnet developed in the 1980s. It has a combination of very high remanence and coercivity, and comes with a wide range of grades, sizes and shapes. With its excellent magnetic characteristics, abundant raw material and relatively low prices, NdFeB offers more flexibility in designing of new applications or replacing the traditional magnetic materials to achieve high efficiency, low cost and more compact devices. A powder metallurgy process is used in producing sintered NdFeB magnets. Although sintered NdFeB is mechanically stronger than Sm-Co magnets and less brittle than other magnets, it should not be used as structural components. Selection of NdFeB is limited by temperature due to its irreversible loss and moderately high reversible temperature coefficient. The maximum application temperature is 200 degrees Celsius for high coercivity grades. NdFeB magnets are more prone to oxidation than any other magnet alloys. If NdFeB magnet is to be exposed to humidity, chemically aggressive media such as acids, alkaline solutions, salts and harmful gases, coating is recommended. It is not recommended in a hydrogen atmosphere.