As early as 2,500 years ago, ancient civilizations discovered the earliest magnets. Magnetic compasses were widely used in navigation in Europe and China in the 12th and 13th centuries AD. Magnets play an important role in modern technology. The market for magnet products continues to grow with growing demand for magnetic circuit components that are widely used in industrial, automotive, scientific and everyday household appliances.
What is magnetism?
Magnetism can be described as a force that attracts and repels magnetic objects. This force is mediated by magnetic fields that penetrate different media. Some materials are inherently magnetic, which is a default property. However, some materials can be magnetized or demagnetized as required.
What substances in metals produce magnetism?
Magnetism is created by the movement of electric charges. It is similar to electric current. When charges spin, they create a small dipole.
If the spins are balanced, the resultant force of these spins is negligible. On the other hand, if there are many unpaired electrons, the magnetic moment becomes very large. This process creates a magnetic field around the metal. Electric currents can also generate magnetic fields. When a current passes through the wire, a circular magnetic field is generated around it. The magnetic field produced by an electric current in the vicinity of a conductor can also be used to generate an electric current. Based on this principle, many innovative devices and applications utilizing magnetism and electricity have been invented. Electromagnetic theory largely explains the progress of modern technology.
Which magnets can be used?
There are many types of magnets. Magnetic metals can be distinguished by how long their properties remain active. Therefore, magnets can be divided into the following categories: permanent magnets, temporary magnets, and electromagnets.
Permanent magnet
When it comes to magnets, the first thing that comes to mind is permanent magnets. Magnetizing these objects creates a magnetic field. Fridge magnets are a good example, and are often attached to refrigerator doors to hang notes. Most permanent magnets contain iron, nickel or cobalt. Permanent magnets are made of two types: "hard" magnets and "soft" magnets. "Hard" magnetic metals tend to remain magnetic for a long time.
Here are some common examples:
AlNiCo magnets are an alloy composed of aluminum, nickel and cobalt. Alnico alloys can be used to make permanent strong magnets. It is widely used in consumer electronics and industry. For example, the material is used in large electric motors, microphones, speakers, electric guitar pickups and microwave ovens. Ferrites are ceramic compounds composed of iron oxide and other elements (strontium or barium). Applications of ferrites include refrigerator magnets and small electric motors.
Neodymium iron boron magnet (NdFeB) is a rare earth magnet composed of an alloy of neodymium, iron and boron. It was invented by General Motors and Sumitomo Special Metals in 1982. The most powerful permanent magnets currently available are neodymium magnets. Applications include cordless tools, hard drives, and magnetic fasteners.
Samarium-cobalt alloys are also rare-earth magnets, often used in specialized applications such as aerospace.
"Soft" magnetic metals can also be magnetized, but quickly lose their magnetism.
Typical examples include iron-silicon alloys and nickel-iron alloys. Materials such as these are commonly used in electronics such as transformers and magnetic shields. The internal structure of a permanent magnet generates a magnetic field. They are generally not easily demagnetized. Ferromagnetic metals can be made into permanent magnets that cannot be lost by external influences. They withstand demagnetizing forces and are therefore relatively stable. The internal structure of magnet materials is key to understanding permanent magnets. A material appears magnetic to the outside world when its magnetic domains are aligned in the same direction. Magnetic domains are tiny sources of magnetism within the structure of a material. The magnetic domains of ferromagnetic materials are aligned in a strong magnet. Similar conditions exist in the interior of the Earth's core, so it acts like a permanent magnet. Note, however, that Earth's geographic north pole is actually its magnetic south pole.
Temporary magnet
A temporary magnet is a magnet that has the same effect as a permanent magnet in a magnetic field, but its magnetism disappears when it leaves the magnetic field. Under certain conditions, temporary magnets can retain their magnetic properties. If these conditions no longer exist, the magnetic field disappears. Examples of temporary magnets include soft materials with low magnetic properties such as annealed iron and steel. They become magnetic when placed in a strong magnetic field. Its force is low. Have you ever seen a paper clip near a permanent magnet? They are held together by permanent magnets, which is how they work. The magnetic field makes the paper clip a temporary magnet that attracts other paper clips. Once the permanent magnet is removed, the paper clip loses its magnetism.
Electromagnet
An electromagnet generates a magnetic field when an electric current passes through it. Their applications are diverse. For example, electromagnets are used in motors, generators, relays, earphones, etc. An electromagnet consists of an iron core surrounded by a coil. By connecting the wires to a power source, a strong magnetic field is created. With ferromagnetic materials, the strength of the magnetic field is further amplified. Depending on the current flow, electromagnets can be extremely strong. The magnetic force can also be turned on and off with the push of a button. Magnetism has many special properties that allow it to be used in a variety of applications.
What are magnets made of?
Magnets are made of a group of metals known as ferromagnetic metals. For example, nickel and iron. What is unique about this class of metals is their ability to magnetize uniformly. By asking how a magnet works, we are referring to how the magnetic field of a magnet acts on an object. The process of finding the answer is quite interesting. Every material contains several small magnetic fields called domains. More commonly, these domains are independent of each other and face different directions. However, when a strong magnetic field is applied, the magnetic domains of all ferromagnetic metals can align, resulting in a stronger magnetic field. Most magnets are made this way.
Which magnets are the strongest?
Rare earth magnets are the strongest magnets ever discovered. Among rare earth magnets, neodymium magnets are the most powerful. As long as the magnetic circuit is in good condition, samarium cobalt magnets can outperform new magnets at high temperatures (around 150°C or above).
What are the factors that affect the strength of a magnet?
Magnet strength is affected by a number of factors including: temperature, radiation, external magnetic fields such as high currents, magnets close to another magnet (repulsion) corrosion - some magnets require a protective coating to prevent them from corroding under high, humidity (For example: NdFeB magnets).
In modern magnet materials, shock and vibration have no effect unless the shock or vibration is strong enough to damage the magnet.
Can a magnet retain its strength permanently?
As long as the magnet is kept away from things that negatively affect its magnetism (such as power cords, other magnets, high temperatures, etc.), it will theoretically retain its magnetism permanently.
Which metals are magnetic?
Magnetic fields can interact with metals in a number of ways. It all depends on the internal structure of the material. There are three main types of metals that interact with magnetic fields: ferromagnetic, paramagnetic, and diamagnetic. Magnets are strongly attracted to ferromagnetic metals, while the rest are not. Paramagnetic metals can also attract magnets, but their attraction is very weak. On the other hand, diamagnetic materials show weak repulsion when brought close to a magnet. Only ferromagnetic metals are considered to be truly magnetic.
List of Magnetic Metals
Some of the most famous magnetic metals are listed below. Some of these materials are always magnetic. However, certain materials, such as stainless steel, do not exhibit magnetism unless they contain a specific chemical composition.
Iron
Ferromagnetic metals, such as iron, are well known. In fact, it is the strongest ferromagnetic metal. It is they that give Earth its magnetism and form an important part of the core. So, the Earth itself acts as a permanent magnet.
There are many factors that affect ferromagnetism. In addition to the electron spin at the atomic level, its crystal structure also plays an important role. If it loses its crystalline structure, iron becomes a non-magnetic metal. Iron has different properties depending on its crystal structure. The α-FE structure of iron's body-centered cubic (bcc) structure makes it ferromagnetic. At the same time, it does not show magnetism in the face-centered cubic (fcc) γ-Fe structure. For example, the β-Fe structure exhibits paramagnetism.
Nickel
Nickel is also a common magnetic metal with ferromagnetic properties. Its compounds are also found in the Earth's core. Nickel has historically been used to make coins. Today, nickel is widely used in batteries, paint, kitchen equipment, telephones, construction, transportation and jewelry. Nickel-iron is a key component of stainless steel and is made of nickel. Nickel is also an integral part of Alnico magnets (made of aluminum, nickel and cobalt).
Cobalt
Cobalt is a ferromagnetic metal. Over the past 100 years, cobalt has been widely used for its excellent magnetic properties. Cobalt can be used to make soft and hard magnets. Cobalt-based magnets have many advantages over other soft magnets. In particular, they have a high saturation point, with a Curie temperature of 950-990°C. Therefore, they can be used under high temperature conditions (up to 500°C). Cobalt alloys are widely used in hard drives, wind turbines, MRI machines, electric motors, actuators and sensors.
Steel
Due to the iron content, steel also exhibits ferromagnetism. Steel is attracted to magnets in most cases. It is therefore also possible to use steel for the production of permanent magnets. For example, EN C15D steel has an iron content between 98.81 and 99.26%. This steel has a high iron content. Thus, the ferromagnetic properties of iron are transferred to steel.
Stainless steel
Some stainless steels are magnetic and some are not. Alloy steels become stainless steels by adding chromium to the alloy. The composition and molecular structure of ferritic and martensitic stainless steels make them magnetic. On the other hand, austenitic steels do not exhibit ferromagnetism due to their molecular structure. Therefore, it can be used in MRI machines. The different nickel content is the main reason for the magnetic variation. Strengthening of the oxide layer improves corrosion protection but also changes the structure of the stainless steel.
Rare earth metal
In addition to the metals mentioned above, some compounds of rare earth elements are also ferromagnetic. Gadolinium, samarium, and neodymium are all magnetic rare earth metals. Combining the above metals with iron, nickel and cobalt creates magnets with different properties. Magnets such as these have specific properties required for certain applications. For example, samarium cobalt magnets are used in turbomachinery and high-performance electric motors.
Which metals are not magnetic?
Only a few metals in the periodic table are magnetic. Other common metals are non-magnetic. Below are a few examples.
Aluminum
Aluminum has the same crystal structure as lithium and magnesium, making it nonmagnetic. All three materials are paramagnetic metals. Although aluminum corrosion can occur in a number of ways, it is inherently resistant to environmental corrosion. Combined with its light weight, this makes it a useful metal in many industries.
Gold
Gold, like most metals, is a diamagnetic metal. All diamagnetic metals, including gold, have a weak magnetic attraction to pure magnets.
Silver
Silver is another non-magnetic metal. Silver's diamagnetism makes it non-magnetic. Metals such as silver are known to have the strongest electrical, thermal and reflective properties. When heated, it becomes very soft and malleable. In addition, it has high corrosion resistance. Today, it is widely used in the manufacture of jewelry and currency. It is also used to make solar panels and water filters.
Copper
Copper itself is not magnetic, but it interacts with magnets in some way (eg: eddy currents). Power plants take advantage of this property of copper to generate electricity. Using this principle, metal detectors can also detect non-magnetic metals such as gold and silver. However, such interactions are clearly insufficient for most practical purposes and limit the number of potential applications.