Magnetization studies of binary and ternary Co-rich phases of the Co–Si–B system

[Display omitted] ▶ Co 5Si 2B phase was found to be paramagnetic, while Fe 5SiB 2 and Mn 5SiB 2 are ferromagnetic. ▶ Ferromagnetic Co 2B phase showed magnetization curves evidence of the easy axis change at ∼ 70 K. ▶ The easy axis change in Co 2B does not happen exactly at 70 K, but depends on the applied field; DT grows with the applied field increasing. CoB, Co 2B, CoSi, Co 2Si and Co 5Si 2B phases can be formed during heat-treatment of amorphous Co–Si–B soft magnetic materials. Thus, it is important to determine their magnetic behavior as a function of applied field and temperature. In this study, polycrystalline single-phase samples of the above phases were produced via arc melting and heat-treatment under argon. The single-phase nature of the samples was confirmed via X-ray diffraction experiments. AC and DC magnetization measurements showed that Co 2Si and Co 5Si 2B phases are paramagnetic. Minor amounts of either Co 2Si or CoSi 2 in the CoSi-phase sample suggested a paramagnetic behavior of the CoSi-phase, however, it should be diamagnetic as shown in the literature. The diamagnetic behavior of the CoB phase was also confirmed. The paramagnetic behavior of Co 5Si 2B is for the first time reported. The magnetization results of the phase Co 2B have a ferromagnetic signature already verified on previous NMR studies. A detailed set of magnetization measurements of this phase showed a change of the easy magnetization axis starting at 70 K, with a temperature interval of about 13 K at a very small field of 1 mT. As the strength of the field is increased the temperature interval is enlarged. The strength of field at which the magnetization saturates increases almost linearly as the temperature is increased above 70 K. The room temperature total magnetostriction of the Co 2B phase was determined to be 8 ppm at a field of 1 T.