Soft magnetic properties of Fe based amorphous thick sheets with large glass forming ability

The thermal stability of the supercooled liquid, glass forming ability (GFA) and magnetic properties were examined for amorphous Fe_72-x,Al₅Ga₂P₁₁C₆B ₄Si_x, Fe₇₂Al₅Ga₂P_11-x,C₆B ₄Si_x, and Fe₇₂Al₅Ga₂P₁₁C_6-xB ₄Si_x alloys. The increases in the thermal stability and GFA and the improvement of the soft magnetic properties were recognized in the replacements of P by 1 to 2 at. % Si and of C by 1 at. % Si. The supercooled liquid region ΔT_x defined by the difference between T_x and T_g increases from 53 K for Fe₇₂Al₅Ga₂P₁₁C₆B ₄ to 58 K for Fe₇₂Al₅Ga₂P₁₁C₅B ₄Si₁. The maximum thickness for glass formation (t_max) by copper mold casting also increases from 1 mm for the Fe-Al-Ga-P-C-B alloy to 3 mm for the Fe₇₂Al₅Ga₂P₁₀C₆B ₄Si₁ alloy. The increases in ΔT_x and t_max are presumably because of the increase in the degree of the satisfaction of the three empirical rules for glass formation. The soft magnetic properties are also improved by the replacement of 1% Si through the increase in the squareness ratio of B-H loop (B_t/B_s) and the decrease in coercive force (H_c). The best soft magnetic properties for the bulk amorphous alloys are 1.14 T for Bs, 1.5 A/m for H_c, 0.45 for B_t/B_s and 594 K for T_c for the Fe₇₂Al₅Ga₂P₁₀C₆B ₄Si₁ alloy. The success of forming the Fe based ferromagnetic bulk amorphous alloys of 3 mm in thickness is promising for future development as a new type of magnetic material.