Magnetic vs Non-Magnetic Metals
Magnetic materials are attracted to a magnet and may even become magnetized. Nearly all magnetic materials are metals. Familiar examples of magnetic metals include iron, nickel, cobalt, and steel. But, magnetism is a complex phenomenon. Not all iron or steel is magnetic. There are even some nonmetals that display magnetism! Here is a review of the types of magnetism, a list of magnetic materials, and a look at metals that aren’t magnetic.
Types of Magnetism
In order to understand which metals are magnetic, it’s helpful to review the five types of magnetism:
Diamagnetism: All matter is diamagnetic, which means it is weakly repelled by a magnetic field. In a magnetic material, the attraction to a magnet exceeds repulsion from diamagnetism.
Paramagnetism: A paramagnetic material is weakly attracted to a magnetic field. Aluminum, oxygen, iron oxide (FeO), and titanium are paramagnetic.
Ferromagnetism: Ferromagnetic materials are strongly attracted to magnets and can become magnetized. Above a temperature called the Curie point, ferromagnetic materials lose their magnetism. Iron, cobalt, nickel, most of their alloys, and some rare earth metal compounds are ferromagnetic.
Ferrimagnetism: Ferrimagnetic materials are attracted to magnets and themselves act as permanent magnets. Above the Curie point, ferrimagnetic materials lose their external magnetism. Lodestones (the mineral magnetite, Fe3O4) are ferrimagnetic.
Antiferromagnetism: In antiferromagnetism, alignment of adjacent ions at low temperatures makes the material insensitive to a magnetic field. However, above a temperature called the Néel temperature, some atoms break free of the alignment and the material becomes weakly magnetic. Manganese oxide (MnO) and pure neodymium are examples of an antiferromagnetic materials.
Usually, when people talk about “magnetic metals,” they’re talking about ferromagnetic and ferrimagnetic metals. But, if you include the conditional and weaker types of magnetism, many more metals (and some nonmetals) are magnetic.
What Metals Are Magnetic?
Magnetic metals include some pure metallic elements and their alloys. Here is a list of some of the most magnetic metals:
Some types of steel (e.g., ferritic stainless steel)
Neodymium, iron, boron alloy (Nd magnet)
Even though both iron and nickel are magnetic, not all steel is magnetic. The crystal structure of an alloy determines its magnetism, so elements that are magnetic on their own don’t necessarily form magnetic alloys.
Iron is considered magnetic, but its behavior depends on crystal structure and temperature. It’s the α form that’s ferromagnetic, and only below its Curie point of 770 °C. γ-iron is antiferromagnetic.
Ruthenium and the actinides (e.g., plutonium, neptunium) are ferromagnetic under certain conditions.
What Metal Is the Strongest Magnet?
The strongest permanent magnetic metal you can buy is a neodymium (Nd) magnet. Neodymium magnets are not pure neodymium. The pure element is paramagnetic at room temperature and antiferromagnetic at very cold temperatures (20 K or −253.2 °C). Neodymium magnets are a neodymium alloy (Nd2Fe14B).
Neodymium alloy magnets lose their magnetism at lower temperatures. Under these conditions, samarium-cobalt (SmCo) magnets are the strongest magnetic metals.
What Metals Are Not Magnetic?
The vast majority of metals are considered “not magnetic.” More accurately, most of these metals are paramagnetic.:
Some types of steel (e.g., austenitic stainless steel, 304 stainless steel)
Platinum (although some of its alloys are magnetic)
All alkali metals (e.g., sodium, lithium)
Manganese (exceptions: weakly magnetic in compounds with Mn2+ cation, ore jacobsite [FeMn),O] is strongly magnetic)
Magnetic behavior depends on conditions. For example, copper metal and salts containing the Cu+ ion are diamagnetic, but copper atoms and salt containing copper ions (Cu2+) are paramagnetic. 304 stainless steel isn’t normally magnetic, but it becomes partially ferromagnetic if it’s bent at room temperature.
Are Any Nonmetals Magnetic?
Nonmetals are generally considered to be non-magnetic. Some types of graphite (an allotrope of carbon) are so diamagnetic they can repel a strong magnet so that it appear to levitate. However, liquid oxygen and boron fullerenes (B80) are paramagnetic. Recently, scientists have developed organic magnets made of fluorographene with hydroxyl groups. These organic magnets are antiferromagnetic at room temperature. Magnetic vs Non-Magnetic Metals