Fracture toughness of commercial magnets

Nd₂Fe₁₄B is currently the best (highest energy product) hard magnet available. Like most permanent magnetic materials, it is rather brittle. The fracture toughness of specimens of commercially available hard magnets were measured using a chevron notch, three-point bend test. Values for Nd₂Fe₁₄B magnets ranged from 2.5 to 5.5 MPa√m. In comparison, SmCo₅ was measured to have a fracture toughness of 1.9 MPa√m. It appears that this testing technique will allow differences in fracture toughness to be measured between alloys with different compositions and fabricated by different production methods and should be able to track the fracture toughness as improvements are made to a particular alloy