Magnetic metals have a variety of purposes but some applications need materials that are non-magnetic. So which is which? Let's find out!
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Let’s take a look at some of the most well known magnetic metals. Some of them are magnetic at all times. Other, like stainless steel, have magnetic properties only with a certain chemical composition.
Iron
Iron is an extremely well-known ferromagnetic metal. It is, in fact, the strongest ferromagnetic metal. It forms an integral part of the earth’s core and imparts its magnetic properties to our planet. That is why the Earth acts as a permanent magnet on its own.
There are many aspects that contribute to iron’s magnetism. In addition to its net electron spin at the atomic level, its crystalline structure also plays an important role. Without it, iron would not be a magnetic metal.
Different crystalline structures result in different iron properties.
Iron is ferromagnetic in its
body-centred cubic (bcc) alpha-FE structure. At the same time, it does not show magnetism in
face-centred cubic (fcc) gamma-Fe structure. Beta-Fe structure, for example, displays paramagnetic tendencies.
Nickel
Nickel is another popular magnetic metal with ferromagnetic properties. Like iron, its compounds are present in the earth’s core. Historically, nickel has been used to make coins.
Today, nickel finds use in batteries, coatings, kitchen tools, phones, buildings, transport and jewellery. A large portion of nickel is used to manufacture ferronickel for stainless steel.
Because of its magnetic properties, nickel is also part of
Alnico magnets (made of aluminium, nickel, and cobalt). These magnets are stronger than rare-earth metal magnets but weaker than iron-based magnets.
Cobalt
Cobalt is an important ferromagnetic metal. For over 100 years, cobalt’s excellent magnetic properties have helped develop a variety of applications.
Cobalt can be used to produce soft as well as hard magnets. Soft magnets that use cobalt have advantages over other soft magnets. Namely, they have a high saturation point, Curie temperatures in the range of 950…990° Celsius. Thus, they can be used for high-temperature applications (up to under 500° Celsius).
Cobalt with its alloys is used in hard disks, wind turbines, MRI machines, motors, actuators, and sensors.
Steel
Steel also displays ferromagnetic properties as it is derived from iron. Most steels will be attracted to a magnet. If needed, steel can also be used to make permanent magnets.
Let’s take the example of steel EN C15D. This grade of steel contains 98.81 to 99.26% iron. Thus, a very high percentage of this steel grade is iron. Hence, the ferromagnetic properties of iron transfer to steel.
Stainless Steel
Some stainless steels are magnetic and some are not. An alloy steel becomes a stainless steel if it has at least 10.5% of chromium in it. Due to the varying chemical compositions,
there are different types of stainless steel.
Ferritic stainless steels
Ferritic and
martensitic stainless steels are magnetic due to their iron composition and molecular structure.
Austenitic steels, on the other hand,
do not display ferromagnetic properties because of a different molecular structure. This makes the suitable for use in MRI machinery.
The structural difference derives from the amount of nickel. It strengthens the oxide layer for better protection against corrosion but also changes the structure of stainless steel.
Rare Earth Metals
Along with the above-mentioned metals, compounds of some rare earth elements also have excellent ferromagnetic properties. Gadolinium, samarium, neodymium are all examples of magnetic rare earth metals.
Various magnets with different properties can be manufactured using the above metals in combination with iron, nickel and cobalt. These magnets come with specific properties necessary for certain applications.
For example, samarium-cobalt magnets are present in turbomachinery, high-end electric motors, etc.
Which Metals Are Not Magnetic?
Only a few metals in the periodic table are magnetic. Most other common metals are non-magnetic metals. Let’s take a look at some of them.
List of Non-Magnetic Metals
Aluminium
Aluminium’s crystal structure, similarly to lithium and magnesium, makes it non-magnetic. All three materials are popular examples of paramagnetic metals.
Although
several types of aluminium corrosion can happen, it is known for its resistance to corrosive environments. This, along with its light weight, makes it a useful metal in many industries.
Gold
Gold is a diamagnetic metal like most other metals. In its pure form, gold is non-magnetic and shows only a weak repulsion towards magnets like all diamagnetic metals.
Silver
Silver is another non-magnetic metal. This property makes identifying fake silver possible. If the “silver” coins or jewellery attracts to magnets, it is something else.
Copper
Is Copper Magnetic?
Copper itself is not magnetic but interacts with magnets to some extent. This property helps generate electricity in power plants.
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