18 research outputs found
SOFT MAGNETIC Fe-BASED METALLIC GLASSES PREPARED BY FLUXING AND WATER-QUENCHING
Abstract. [(Fe 0.5 Co 0.5 ) 0.75 B 0.20 Si 0.05 ] 96 Nb 4 soft magnetic bulk metallic glasses were prepared by fluxing and water-quenching in a silica tube. Dimension of the bulk metallic glass specimens was up to 7.7 mm in diameter, which is about 1.5 times larger than those prepared by Cu mold-casting. The critical cooling rate of [(Fe 0.5 Co 0.5 ) 0.75 B 0.20 Si 0.05 ] 96 Nb 4 alloys with fluxing for forming a metallic glass phase was 150 -170 K/s, which was considerably smaller than that without fluxing. Saturation magnetization was 1.13 T, and coercivity was lower than 20 A/m. Fluxing suppresses heterogeneous nucleation by isolating the nucleation sites from the molten alloys and improves their glass-forming ability
Probing a ferromagnetic critical regime using nonlinear susceptibility
The second order para-ferromagnetic phase transition in a series of amorphous
alloys (Fe{_5}Co{_{50}}Ni{_{17-x}}Cr{_x}B{_{16}}Si{_{12}}) is investigated
using nonlinear susceptibility. A simple molecular field treatment for the
critical region shows that the third order suceptibility (chi{_3}) diverges on
both sides of the transition temperature, and changes sign at T{_C}. This
critical behaviour is observed experimentally in this series of amorphous
ferromagnets, and the related assymptotic critical exponents are calculated. It
is shown that using the proper scaling equations, all the exponents necessary
for a complete characterization of the phase transition can be determined using
linear and nonlinear susceptiblity measurements alone. Using meticulous
nonlinear susceptibility measurements, it is shown that at times chi{_3} can be
more sensitive than the linear susceptibility (chi{_1}) in unravelling the
magnetism of ferromagnetic spin systems. A new technique for accurately
determining T{_C} is discussed, which makes use of the functional form of
chi{_3} in the critical region.Comment: 11 Figures, Submitted to Physical Review
Effect of Yttrium Addition on Glass-Forming Ability and Magnetic Properties of Fe–Co–B–Si–Nb Bulk Metallic Glass
The glass-forming ability (GFA) and the magnetic properties of the [(Fe0.5Co0.5)0.75B0.20Si0.05]96Nb4−xYx bulk metallic glasses (BMGs) have been studied. The partial replacement of Nb by Y improves the thermal stability of the glass against crystallization. The saturation mass magnetization (σs) exhibits a maximum around 2 at. % Y, and the value of σs of the alloy with 2 at. % Y is 6.5% larger than that of the Y-free alloy. The coercivity shows a tendency to decrease with increasing Y content. These results indicate that the partial replacement of Nb by Y in the Fe–Co–B–Si–Nb BMGs is useful to simultaneous achievement of high GFA, high σs, and good soft magnetic properties