Magnetic anisotropy - How much is enough for a permanent magnet?

Material choices for permanent magnets are analyzed in terms of energy product, anisotropy and hardness parameter. Energy product is the main consideration for permanent magnets, because the purpose of a magnet is to store magnetostatic energy and create as much flux as possible in the surrounding space. Magnet processing is easiest if the hardness parameter is significantly greater than one. The anisotropy requirement becomes increasingly stringent for large M-s and K-1 values of Ito 2 MJ/m(3) may be insufficient. Some potential new magnets and alternative strategies to develop magnetic hardness are discussed. (C) 2015 Elsevier Ltd. All rights reserved.