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

The magnetocrystalline anisotropy constants, K
1
, 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 K
1
is negative at -196°C and the magnitude is fairly large (e.g.
\approx10^{4}
erg/cm
³
) for most alloys examined. However, with increasing temperature, K
1
crosses zero and changes its sign from negative to positive. It should be noted that the temperature at which K
1
crosses zero,
T_{K_{1}}
=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),
T_{K_{1}}
=0 was found to be room temperature. No sign change of K
1
took place in the 7.4wt%Si, 4.1wt% Al, bal.Fe alloy.
T_{K_{1}}
=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 K
1
becomes zero are strongly temperature dependent. With increasing temperature, the composition-line of K
1
=0 shifts to Al rich and Si less concentration portion in the Fe-Si-Al ternary alloy system.