TITLE:
Thermal Behavior and Magnetic Properties of Nd-Fe-B Based Exchange Spring Nanocomposites Nd4-xTbxFe83.5Co5Cu0.5Nb1B6 (x = 0, 0.2, 0.4, 0.6, 0.8 and 1) Melt-Spun Ribbons
AUTHORS:
Palash Chandra Karmaker, Mohammad Obaidur Rahman, Nguyen Huy Dan, Samia Islam Liba, Per Nordblad, Dilip Kumar Saha, Sheikh Manjura Hoque
KEYWORDS:
Coercivity, Maximum Energy Product, Remanent Ratio, Nanocomposite, Hard and Soft Phases
JOURNAL NAME:
Advances in Materials Physics and Chemistry,
Vol.7 No.6,
June
12,
2017
ABSTRACT: Co-rich
Nd-Fe-B nanocomposite ribbons with Tb substituted have been fabricated by
single roller melt spinning technique of Nd4-xTbxFe83.5Co5Cu0.5Nb1B6 (x = 0, 0.2, 0.4, 0.6, 0.8 and 1) alloys in an argon (Ar) atmosphere at a
circumferential speed of 40 m/s. According to the differential scanning
calorimeter (DSC) traces the nanocomposite samples have been annealed at
different temperatures like 675°C, 687°C, 700°C, 712°C and
725°C for 10 min. Crystallization behavior was studied by X-ray diffraction in
which it was found that the XRD patterns are characterized by broad diffused
pattern which demonstrate the amorphous state of materials. The ribbon samples
were also characterized by vibration sample magnetometer (VSM) and Mössbauer
spectroscopy at as-cast and annealed condition. Co-rich and Tb substitution has
significantly enhanced the value of coercivity (Hc) and maximum
energy product (BH)max. Highest value of Hc and (BH)max has been obtained as 2.36 kOe and 6.11 MGOe for the sample annealed at 700°C for 10
min with higher concentration of Tb. The M-H hysteresis loops show extremely
soft natures which do not possess any area. We have found reduced remanent
ratio (Mr/Ms) up to 0.49 at optimal annealing temperature
700°C. However, with the annealing of the samples in the above mentioned
temperature, evolution
of large coercivity was observed due to the formation of exchange couple hard
and soft nanocrystal composites. We have investigated the variation of Curie
temperature (Tc) with annealing temperature of the melt spun ribbon
samples. Mossbauer spectroscopy was carried out to study the hyperfine
parameters such as hyperfine field, hyperfine field distribution for full width
half maximum (FWHM) and isomer shift of Fe species of these two phases.