Ti-Doped Nanocomposite Pr₂Fe₁₄B/-Fe Ribbons with High Coercivity

Nanocomposite Pr9.5Fe84-xB6.5Tix(x = 1, 2, 3, 4) permanent magnetic alloys are prepared by the melt-spinning technique with wheel speed ranging from 21 to 33 ms(-1). X-ray diffraction results show that the as-spun ribbon is rich of soft alpha-Fe, hard Pr2Fe14B magnetic phases, and no other metastable phases are found in our alloy ribbon. Initial magnetization curves reveal that the coercivity mechanism of the ribbons vary with the content of Ti. For x = 2, coercivity is mainly determined by pure pinning; while for x = 1, 3, and 4, it is mainly controlled by the mixture of nucleation of domain and localized pinning at grain boundaries. The coercivity value of 1026 kA m(-1), the highest value reported so far, is mainly generated from a pure pinning mechanism in the ribbon with x = 2. The recoil permeability shows a minimum value range from 2.508 x 10(-4) to 1.123 x 10(-4) T/kAm(-1) for x = 2 alloy, suggesting strong exchange coupling between the magnetic grains and then leading to the concurrent reversal of soft and hard phase grains during the demagnetization process. The Henkel plots demonstrate only exchange interaction for x = 1 and exchange interaction with slightly magnetostatic interaction for x = 2, 3, and 4. The exchange interaction exhibits maximum strength for x = 2, which is the reason for high coercivity.