[01] Palash Chandra Karmaker, Department of Physics, Jahangirnagar University, Savar, Dhaka, Bangladesh; Materials Science Division, Atomic Energy Center, Dhaka, Bangladesh; Department of Electrical and Electronic Engineering, University of Information Technology & Sciences, Dhaka, Bangladesh. [02] Mohammad Obaidur Rahman, Department of Physics, Jahangirnagar University, Savar, Dhaka, Bangladesh. [03] Nguyen Huy Dan, Institute of Materials Science, Vietnam Academy of Science and Technology, Hanoi, Vietnam. [04] Samia Islam Liba, Materials Science Division, Atomic Energy Center, Dhaka, Bangladesh. [05] Per Nordblad, Solid State Physics, Department of Engineering Science, Uppsala University, Uppsala, Sweden. [06] Sheikh Manjura Hoque, Materials Science Division, Atomic Energy Center, Dhaka, Bangladesh.

Tb substituted amorphous ribbons of composition Nd_4-xTb_xFe_71+yCo₅Cu_0.5Nb₁B_18.5-y (x=0.4; y=12.5 and 0) prepared by a melt spinning technique in an Ar atmosphere has been studied to observe the exchange coupled soft and hard magnetic phases in the nanocrystalline state. For thermal analysis of the ribbon samples differential scanning calorimeter (DSC) was used in order to determine the crystallization temperatures. Significant changes in the crystallization temperatures are observed in the DSC traces due to the difference in B (Boron) content of two batches of composition. The samples were characterized by X-ray diffractometer (XRD) with CuK _α radiation and vibrating sample magnetometer (VSM) of as-quenched and annealed condition during 10 minutes. Structure and magnetic properties of the ribbons clearly depend on their composition. Glass forming ability (GFA) of the alloys is decreased with decreasing B-concentration. Coercivity (H _c) and maximum energy product (BH) _max of the alloys is significantly enhanced by increasing B-concentration. The optimal annealing conditions for the best hard magnetic performance of the ribbons were obtained. The composition dependence of the structure and magnetic properties of the alloys was discussed.

Exchange-Spring Magnets, Soft and Hard Phase, Coercivity, Maximum Energy Product, Crystallization Temperature

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