Crystallization, morphology and magnetic properties of melt-spun (Nd,Pr,Dy)/sub 2/(Fe,Co,Mo)/sub 14/B//spl alpha/-Fe nanocomposites
Crystallization, phase evolution, nanostructure, exchange coupling, and hard magnetic properties of melt-spun Nd/sub 2.4/Pr/sub 5.6/Dy/sub 1/Fe/sub 85/B/sub 6/ and Nd/sub 2.4/Pr/sub 5.6/Dy/sub 1/Fe/sub 78/Co/sub 6/Mo/sub 1/B/sub 6/ nanocomposites have been studied. All the Nd/sub 2.4/Pr/sub 5.6/Dy/sub 1/Fe/sub 85/B/sub 6/ alloys annealed for 30 s at 565/spl deg/C or above contain nanostructured /spl alpha/-Fe and Nd/sub 2/Fe/sub 14/B-type (2:14:1) phases, whereas Nd/sub 2.4/Pr/sub 5.6/Dy/sub 1/Fe/sub 78/Co/sub 6/Mo/sub 1/B/sub 6/ alloys annealed at 600/spl deg/C or below are mainly composed of /spl alpha/-Fe and a metastable 1:7 phase. A small amount of 2:14:1 phase forms after annealing at 600/spl deg/C. When annealed at 640/spl deg/C or above, the hard phase in Nd/sub 2.4/Pr/sub 5.6/Dy/sub 1/Fe/sub 78/Co/sub 6/Mo/sub 1/B/sub 6/ alloys is the 2:14:1 phase rather than the 1:7 phase. The differences in magnetic properties of the Nd/sub 2.4/Pr/sub 5.6/Dy/sub 1/Fe/sub 85/B/sub 6/ and Nd/sub 2.4/Pr/sub 5.6/Dy/sub 1/Fe/sub 78/Co/sub 6/Mo/sub 1/B/sub 6/ nanocomposites at different anneal temperatures result from the different nanostructures, exchange coupling and phase components present in the alloys, in particular from the different amount of the 1:7 phase.
Effect of a high magnetic field on hard magnetic multilayered Fe-Pt alloys
Abstract Fe-50 vol%Pt multilayers that were prepared by accumulative roll-bonding were annealed in vacuum for 2 h at various temperatures between 723 K and 823 K. Some samples were annealed without any high magnetic field (HMF). Others were subjected HMF up to 31.2 T, applied in either in-plane or out-of-plane directions. The annealing partially transformed the original multilayered structure into a polycrystalline hard-magnetic FePt magnetic phase with ordered L10 structure. Textured FePt/Fe nanocomposite foils were formed under HMF. Magnetic anisotropic behavior was observed in the annealed FePt/Fe composite because of the textured nanostructure. HMF annealing decreased grain size and increased the (0 0 1) texture along the HMF direction. In the sample annealed with out-of-plane HMF, both coercivity and maximum energy product were enhanced because of higher (0 0 1) out-of-plane texture and finer nanoscaled grain sizes compared to other samples. An in-plane HMF appeared to strongly inhibit phase transformation. This inhibition likely resulted from a change in Gibbs free energy and the diffusion inhibition caused by HMF.
High‐energy product ThMn12 Sm‐Fe‐T and Sm‐Fe permanent magnets synthesized as oriented sputtered films
Binary SmFe12 and Sm(Fe,T)12 films, where T =Ti and V, crystallized into the ThMn12‐type structure, have been synthesized as sputtered films such that the c axes of the crystallites are oriented perpendicular to the film plane. It has been possible to synthesize Sm(Fe,T)12 films which exhibit a very dominant (002) texture with intrinsic coercivities of 5 or more kOe. Such films exhibit flux densities 4πMs of more than 10 kG perpendicular to the film plane. No discernible columnar structure is exhibited so that the static energy product measured perpendicular to the film plane is nearly 21 MGOe.