Magnetocrystalline anisotropy for Fe-Al-Si (Sendust) single crystals with DO3ordered structure

The magnetocrystalline anisotropy constants, K1, of the Sendust alloys (7∼11wt%Si, 4∼7wt%Al, bal.Fe) were determined as a function of the temperature between -196°C and 600°C by means of a torque magnetometer. The sign of K1is negative at -196°C and the magnitude is fairly large (e.g. erg/cm³) for most alloys examined. However, with increasing temperature, K1crosses zero and changes its sign from negative to positive. It should be noted that the temperature at which K1crosses zero, =0, differs remarkably and ranges from -140°C to 200°C for each alloy composition. For the central composition of the Sendust alloy (9.6wt%Si, 5.7 wt%Al, bal.Fe), =0 was found to be room temperature. No sign change of K1took place in the 7.4wt%Si, 4.1wt% Al, bal.Fe alloy. =0 for the alloys quenched from 1200°C is found to different from that of the alloys annealed at 1200°C. The compositions at which K1becomes zero are strongly temperature dependent. With increasing temperature, the composition-line of K1=0 shifts to Al rich and Si less concentration portion in the Fe-Si-Al ternary alloy system.