The role of nonmagnetic phases in improving the magnetic properties of devitrified Pr_2Fe_(14)B-based nanocomposites

摘要

The structure-property relationship of devitrified Pr_9Fe_(8.15)Ti_(2.5)B_7 (low-B) and Pr_9Fe_(73.5)Ti_(2.5)B_(15) (high-B) nanocomposite ribbons with high coercivity has been investigated. The introduction of excessive B leads to an obvious increase of the amount of TiB_2 nonmagnetic phases. TEM observation shows that TiB_2 is mainly distributed in the Pr_2Fe_(14) 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.