Ferromagnetic decagonal Mn-Al-Ge-B-Fe quasicrystals with high coercive force

A ferromagnetic decagonal phase with high coercive forces exceeding 80kA/m (1 kOe) was found to form in rapidly solidified Mn_45-x,Al₂₅Ge₁₅B₁₅Fe_x (x=10 and 15 at%) alloys. The decagonal alloy containing 15 at%Fe consists of fine grains with sizes of 5 to 20 nm and has the periodic lattice spacing of 1.2 nm along the c-axis direction. Furthermore, the decagonal phase contains a high density of internal defects and the electron diffraction patterns consist of reflection spots with significant streaks along the < 100000) direction in the quasilattice a-b plane. The decagonal Mn₃₀Al₂₅Ge₁₅B₁₅Fe₁₅ alloy exhibits ferromagnetic properties of 2.89 × 10^-5 Wb m/kg for magnetization under a field of 1432 kA/m (J₁₄₃₂), 1.38 × 10^-5 Wb m/kg for remanence (B_r), 114 kA/m for intrinsic coercive force (₁H_c), 1.4kJ/m³ for maximum energy product (B//)mas and 620 K for Curie temperature (7;). The high coercive force is presumably due to the formation of the nanoscale ferromagnetic decagonal grains containing a high density of phason defects. The first success of synthesizing the ferromagnetic decagonal alloy with the hard magnetic characteristics is encouraging for future progress of quasicrystalline alloys as a new type of engineering material.