Magnetic/Magnetostrictive Properties Together with Resistivity and Corrosion Behaviors of CoFe2 and Its Composite with CoFe2N

The CoFe2 alloy (CF) was prepared by reducing CoFe2O4 in the H2 ambient. Subsequently the CF sample was nitrided in the NH3 atmosphere to produce the composite of CoFe2N and CoFe2. The magnetostriction, thermal expansion, resistivity and corrosion resistance of CF sample and the nitrided sample (CFN) at 1000 °C were investigated. The saturation magnetostriction coefficiency λs and thermal expansion coefficient α at 300 K for the nitrided CFN were 50 ppm and 10 ppm/K, respectively, approximately equal to those for the CF sample. However, compared with CF, CFN presents a decrease in temperature coefficient Rλ (300 K) of magnetostriction by ~11%. The smaller resistivity and improved corrosion resistance in the H2SO4 solution may expand the applications of the CoFe2 in the fields needing lower resistivity or in the acidic environment.