China Neodymium And Ferrite Magnets Manufacturer & Supplier 
Ring permanent magnets are widely used in motors, sensors, speakers, etc. Some users have asked the question which type of ring magnet has the strongest magnetic strength, the following will be introduced from the material, the design of the inner hole.
First of all, from the magnetic material, that must be neodymium-iron-boron material, is currently the strongest commercial permanent magnet material, so neodymium ring magnets have a strong pulling force and suction.
Ring magnets with nickel plated surface
In addition to the material, the design of the hole will also have an effect on the magnetic properties. When a ring magnet has a small bore, its magnetic strength will be greater because a smaller bore means that there is more magnetic material remaining, the overall magnetic flux is higher and the surface magnetic data is higher.
A ring magnet with a larger inner diameter is less magnetic because more space is taken up by the “hollow” part, reducing the amount of magnetic material available. For the same material and form factor, an increase in inner diameter results in a decrease in magnetic induction.
NdFeB ring magnets have the strongest magnetic properties, but they need to be selected in combination with the bore design, temperature, cost and other factors. If you only pursue magnetic field strength, give priority to high grade NdFeB (N52/N54) and reduce the bore diameter; if you need high temperature resistance or low cost, adjust the material program, such as samarium cobalt or other.
Practical application examples;
Motor/Generator: NdFeB ring magnets (high magnetic energy product to improve efficiency).
High temperature sensors: SmCo ring magnets (high temperature resistant and stable).
Note: When ring magnets are used in motors, the bore needs to match the rotating shaft; Small holes may be required in magnetic sensors to concentrate the magnetic field.
Past Ring Magnet Related Articles;
Advantages and Disadvantages of Ring Integral Magnets
Do radiating magnetic rings have to be wound? Why?