All magnets have a specific energy density that can be measured, and not surprisingly, some of these magnets have a greater strength than others. Take your everyday fridge magnet. These magnets can easily hold up small notes or postcards, but it would be impossible for them to hold a full newspaper or cardboard box. A magnet with a stronger magnetic strength would be needed for heavier objects.
It is the same idea when purchasing magnets for specific jobs. If you wish to have the magnet strong enough to stand up to a larger load, you will need a stronger magnet.
Magnets are made from various materials with the most common ones being Ferrite (Ceramic), Alnico, Samarium Cobalt, and Neodymium Iron Boron, also known as NIB.
Why is Energy Density Important?
Knowing the energy density of a specific magnet type allows engineers as well as your everyday hobbyist or school science departments to know which type of magnet is necessary for the job/project they wish to embark on. Although one of these magnets are called "strong" magnets, this in no way means that other magnets are weak. All magnets have a certain amount of strength depending on their energy density but there is only one truly "strong" magnet and this one is the Neodymium Iron Boron or NIB magnet. The actual term "strong" magnet refers to this rare earth magnet known as NIB magnets which are the actual strongest magnets on earth.
These NIB magnets are called "rare earth magnets" because they are made up of rare earth element alloys of neodymium, iron and boron.
The Energy Density of Specific Magnets
If we look at the energy density of the magnets on the market today, we will see a substantial difference from a strong magnet such as Ferrite to the "Strong" magnet of Neodymium Iron and Boron. BHmax is the term used to describe the overall strength of the magnets. The BHmax for each magnet type is listed below.
- Ceramic or Ferrite: BHmax is 3.5
- Alnico: BHmax is 5.5
- Samarium Cobalt: BHmax is 26
- Neodymium Iron Boron: BHmax is 40
We can clearly see from the list above that although a Ceramic magnet is strong, compared to the Neodymium Iron Boron magnet there is a significant difference in BHmax, or energy density. This is why the NIB is known as the "strong" magnet. Whenever you hear someone use the term "Strong" magnet, you will now know that they are most probably referring to the rare earth magnet known as the NIB magnet.
Is There a Reason People Don't Use The NIB Magnet For Everything?
These "strong" magnets are extremely powerful. When you use them, care must be taken at all times. Their intense energy density is not necessary for many situations. Often, Ceramic or Anilco magnets would be a much better alternative.
As you can see from the information given above, there are a variety of magnets on the market. These come in various sizes and different grades, but there is only one magnet that is known as a "strong" magnet. Now you know what exactly a "strong" magnet is.