While PMs are in principle highly durable and fit for a circular economy, this is more complex in practice. PMs come in various types, some of the most powerful ones containing Rare Earth Elements (REE) which is the focus here. Common REE PMs include sintered Neodymium Iron Boron magnets (NdFeB) and Samarium Cobalt magnets (SaCo) of different sub-types.

To complicate things further, PMs come in numerous grades, reflecting their strength and heat resistance. Once the magnet alloy has been formed into a PM it often needs to be coated to protect it from corrosion. This is typically the case with NdFeB magnets, as they contain iron (Fe) which is highly corrodable. There are more than 20 types of PM coatings used for NdFeB magnets (see table).

PMs are also designed with different orientations of the magnetism, to fit the design of the motor or generator it is intended for. This adds another layer of diversity to the PM stock found in the economy.

The different PM characteristics affect the reusability and recyclability of the magnets. Hence, the key message is that to enable the reuse and/or recycling of PMs, downstream actors engaged in revalorization of used PMs need to have access to accurate information about what is contained in the magnets recovered from products, their characteristics and technical properties.