1996 Volume 37 Issue 4 Pages 559-563
A ferromagnetic decagonal phase with high coercive forces exceeding 80 kA/m (1 kOe) was found to form in rapidly solidified Mn45−xAl25Ge15B15Fex (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 (Br), 114 kA/m for intrinsic coercive force (iHc), 1.4 kJ/m3 for maximum energy product (BH)max and 620 K for Curie temperature (Tc). 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.
