The role of nonmagnetic phases in improving the magnetic properties of devitrified Pr2Fe14B-based nanocomposites

The structure–property relationship of devitrified Pr9Fe81.5Ti2.5B7 (low-B) and Pr9Fe73.5Ti2.5B15 (high-B) nanocomposite ribbons with high coercivity has been investigated. The introduction of excessive B leads to an obvious increase of the amount of TiB2 nonmagnetic phases. TEM observation shows that TiB2 is mainly distributed in the Pr2Fe14B hard magnetic phase, which strongly hinders the domain wall movement and keeps a strong intergrain exchange coupling action among the magnetic phases. Thus, the coercivity is significantly increased by 111% from 4.6 kOe for low-B ribbons to 9.7 kOe for high-B ribbons due to increased B addition. The squareness of the demagnetization curves is also improved, simultaneously and the remanence remains almost constant. Hence, an evidently increased energy product is attained for the devitrified high-B ribbons. The distribution of nonmagnetic phases plays a key role in the improvement of the hard magnetic properties.