Permanent magnets are different than non-permanent magnets in that they do not lose their magnetism under “normal” circumstances. They will not lose their magnetism if dropped or exposed long-term to other magnets. However, they will lose some or all of their magnetism if exposed to temperatures above their operating range (see explanation of ratings and temperature ranges below).
Most people use the term “permanent magnet” and “neodymium magnet” interchangeably. While it is correct that all neodymium magnets are permanent magnets, not all permanent magnets are neodymium magnets. Neodymium magnets are but one type of permanent magnets. This article will concentrate on neodymium magnets, as they are the most common type of permanent magnet used for alternative energy generation.
Neodymium magnets were developed in the early 1980’s by General Motors and Sumitomo Special Metals to replace the samarium cobalt permanent magnets that were very expensive to produce. They are currently the strongest type of permanent magnets.
There are 6 grades of neodymium magnets. For complete information about neodymium magnets, refer to this helpful chart from K&J Magnets. Some helpful decoding information to know when reading the chart is also provided by K&J.