Abstract
The magnetocrystalline anisotropy constants, K1, of the Sendust alloys (7∼11 wt% Si, 4∼7 wt% 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 K1 is negative at −196°C and the magnitude is fairly large (e.g., −3 × 104 erg/cm3) for the most alloys examined. However, with increasing temperature, K1 crosses zero and changes its sign from negative to positive. It should be noted here that the temperature at which K1 crosses zero, TK1=0, differs distinguishably and ranges from −140°C to 200°C for each alloy composition. For the central composition of the Sendust alloy (9.6 wt% Si, 5.7 wt% Al, bal Fe), TK1=0 was found to be room temperature. No sign change of K1 took place in the case of the 7.4 wt% Si, 4.1 wt% Al, bal Fe alloy. The compositions at which K1 becomes zero are strongly temperature dependent. With increasing temperature, the compositional line of K1=0 moves to the area with rich A1 and less Si concentration in the Fe-Si-Al ternary alloy system. Temperature dependence of K1 for these alloys were discussed in connection with the two components of K1 consist of long range and short range order term in D03 phase.
