Several elements are attracted by magnets. These elements are called magnetic. Magnetic materials are magnetized and widely used for producing different types of permanent magnets. There are different categories of magnetic materials including magnetically soft or magnetically hard materials. Materials that are magnetically soft are easy to magnetize. However, the induced magnetism is temporary because the iron atoms are aligned in the same direction temporarily.
On the other hand, magnetically hard materials can be magnetized by using a strong external magnetic field. Materials that magnetically hard have an indefinite magnetization unless demagnetized. These materials are typically used for producing a wide range of permanent magnets composed of rare earth elements, cobalt, nickel, iron, boron, neodymium, and more. Permanent magnet atoms are not easy to align, thus, it is difficult to magnetize. However, if its atoms are aligned, they remain indefinitely.
5 Magnetic Material Classifications
Magnetic materials are classified through their magnetic behaviour. There are 5 different magnetic material classification depending on its bulk magnetic susceptibility. The materials will have different reaction when placed in a magnetic field due to its different atomic structure. Magnetic material’s magnetic behaviour can be determined its number of each atom’s electrons in its simplest form. Magnetic materials are classified as paramagnetic, diamagnetic, ferromagnetic, ferrimagnetism, and antiferromagnetism.
These materials have small magnetic field susceptibility. Therefore, they are attracted by the magnetic field slightly. Paramagnetic materials do not maintain their magnetic properties if the external magnetic field is removed. One Example of paramagnetic materials is tin magnesium, aluminum, and more. The positive but small relative permeability. They can only be magnetized if it is placed in an area with a very strong magnetic field. Its magnetization is very small due to its incomplete parallel dipole orientation.
This material will repel an externally applied magnetic field. Diamagnetic material’s magnetic domains are realigned. Thus, an opposing magnetic field is externally applied especially when influenced by a magnetic field. Several materials possess diamagnetic properties but the effect on the materials is unnoticed and weak. All the diamagnetic material atom electrons are paired. Thus, diamagnetic materials do not generate their own net magnetic field. Most periodic table elements have diamagnetic properties.
Ferromagnetic materials can generate their own net magnetic field due to their unpaired atom electrons. It’s albeit very weak due to the group or individual atoms being aligned randomly. Therefore, canceling each other. If a ferromagnetic material is applied with the external magnetic field, the external field is removed. Thus, it can maintain its magnetism referred to as remanence. Typical examples of ferromagnetic materials are cobalt, nickel, and iron. These magnetic materials have very high permeability.
Ferrimagnetism is a complex form of magnetic ordering that occurs as a crystal structure ionic compound results such as oxides. The magnetic system of ferrimagnetism consists of two magnetic sublattices. For ferrimagnets, the sublattice’s magnetic moments are not equal. Thus, resulting in a net magnetic moment. It shows all behavior of ferromagnetic materials including remanence, hysteresis, curie temperature, and spontaneous magnetization. The most popular ferrimagnetic material is magnetite.
The magnetic ordering that occurs when the net moment is zero and that sublattice magnetic moments are opposite and equal are called antiferromagnetism. The most widely known clue to antiferromagnetism is the Neel temperature. Hematite is a popular type of antiferromagnetism material. The corundum structure is where the hematite crystallizes in a hexagonal close pack framework with oxygen ions. Chromium is the only element in the periodic table that shows antiferromagnetism properties.
Core Materials
Magnetic materials that are to be used for a specific component will vary on the purpose or functionality. The magnetic materials that will be used as a core must possess a high relative permeability. It is important to remember that soft materials are widely used for applications such as transformers and inductors. On the other hand, hard materials are usually used for producing a wide range of permanent magnets.
Core Shapes
Core shapes can be employed depending on the choice of magnetic materials for the power electronic component designs. There are different magnetic shapes available for different applications such as the following:
- Pot
- E-core
- EC-core
- U-core
- Rings, and more
Lists of Different Magnetic Metals
The most ferromagnetic metal is iron. Iron is also the strongest type of ferromagnetic metal. There are several aspects that affect the iron’s magnetism. Aside from that, the different crystalline structures are factors that act in varying iron properties.
Nickel is also ferromagnetic metal with compounds found in the earth’s core. Nickel is considered part of Alnico magnets because of its magnetic properties. These materials are weaker compared to iron-based attractions but stronger than rare earth.
Cobalt is considered an essential ferromagnetic material. These materials have superior magnetic materials making them suitable for different applications. It can be used for manufacturing both hard and soft magnets. Soft magnets made from cobalt have advantages including high curie temperature and saturation. Magnets made from cobalt are widely used for sensors, actuators, motors, MRI machines, wind turbines, and more.
Steel materials also have ferromagnetic properties. It is also suitable for creating permanent magnets. ENC150 steel grade contains up to 99.26% iron. Thus, making it ferromagnetic materials.
It is a steel alloy that contains at least 10.5% chromium. The most common types of stainless steel are ferritic and austenitic. Ferritic stainless steel is a magnetic material because of its molecular structure and iron composition. On the other hand, austenitic stainless steel is not ferromagnetic metal. Stainless steel materials are magnetic, although some are not.
Rare earth metals that have superior ferromagnetic properties include neodymium, samarium, and gadolinium. These materials can produce magnets using a combination of cobalt, nickel, and iron. An example of the combination of materials is samarium-cobalt magnets that are used in electric motors and turbomachinery.
Magnetic Material Susceptible Value
Magnetic Raw Materials
All the types of magnets in the world are made from different materials varying in characteristics. This guide will provide more information about other raw materials for permanent magnet production.
Ferrite (FE)
Ferrite is used to describe pure iron materials. It also refers to the compound of iron oxide, barium, or strontium carbonate. Magnets made from ferrite materials are guaranteed to have low production costs. However, these magnets are weaker compared to rare earth magnets. These magnets are widely used for applications that do not require high magnetic performance.
Manufacturing
During the production of ferrite magnets, the finely powdered strontium carbonate and iron oxide are calcined to create a metallic oxide material. The fine powder is milled many times once cooled to achieve 2 microns of fine particles. Then, the powder is pressed and compacted in a die. After pressing, the packed particles are sintered before magnetizing.
Magnetic Properties
Ferrite magnets are weaker than rare earth magnets such as neodymium. However, these magnets are widely used in different commercial applications. These are also resistant to corrosion and demagnetization.
AlNiCo
It is an acronym for the primary elements that includes aluminum, nickel, and cobalt to produce AlNiCo magnets. These magnets are widely used for louspeakers, generators, motors, and more.
Manufacturing
AlNiCo magnets are manufactured using two different methods such as the following:
1.Casting
The material for magnet production is molten and poured into a specific mold. When it cools down, the shell of the mold are burned and disintegrated. The magnet cavities inside the mold are integrated with runners so the molten materials can reach to the cavity. All the casted magnets are removed from the molds and placed into magnetizers. After that, the produced magnets are cured in a tempering oven for stabilization. The last process for casting production method is inserting the magnet into solenoid or coil.
2.Sintering
Sintering process involves milling the materials to create a finely ground tiny particles. The magnetic materials that are finely ground are pressed in a die using a pressure. Thus, achieving the desired shape. After pressing, a furnace is used for sintering the material at hydrogen atmosphere. The last step in sintering process includes magnetizing the newly formed magnets inside a coil or solenoid.
Magnetic Properties
- Exceptional magnetic stability
- Less magnetic strength loss
- Highest maximum operating temperature
- Susceptible to demagnetisation
Neodymium (NdFeB)
Neodymium materials are part of a rare earth element. This material is a mixture of boron and iron as well as other traces of praseodymium and dysprosium. Thus, creating a ferromagnetic alloy that is widely known as Nd2Fe14b. This is considered as the strongest magnet. Neodymium magnets are widely used for industrial and commercial applications.
Manufacturing Methods
The mined rare elements are refined through different chemical processes. After refining, the neodymium material is combined with boron, iron, and other elements to create different magnet grade. These are heated until molten in a vacuum induction furnace. Then, the molten material is cooled down before milling. The next step is pressing the super-fine powder in a mold that is exposed to magnetic field.
Magnetic Properties
- Strongest magnets
- High power weight to volume ratio
- Low cost unit of strength
- Superior resistance to demagnetization
- Low maximum operating temperature
- Includes grades with special high operating temperature
Samarium Cobalt
Samarium cobalt is abbreviated as SmCo. This is a magnetic material that is also a part of rare earth elements. SmCo is an alloy of different elements including hard metal cobalt and samarium with traces of praseodymium, zirconium, hafnium, and more.
Manufacturing Methods
Typically, a SmCo magnet is produced using melting and reduction method. Then, these are bonded and sintered to form into a magnet. The most common method for SmCo production is sintering. In this method, the raw materials are heated in an induction furnace to melt. The molten materials are poured in a mold and then cooled down to create an ingot.
The ingots are jet milled to create micron-sized samarium cobalt particles. After that, the fine SmCo particles are pressed using die pressing or isostatic pressing. After pressing, the materials are sintered to make the powder into solid. After cooling down, the produced magnet is applied with magnetic field.
Magnetic Properties
- Available in two types of grades
- Possessed high magnetic strength
- Has excellent maximum energy product
- Maintains high performance in high temperature
- Resistant to corrosion without coating