Structural and magnetic properties of Co2FeAl1−xSix

This work reports about the structural and magnetic properties of the quaternary Heusler alloy Co2FeAl1−xSix with varying Si concentration. The structure of the Co2FeAl1−xSix solid solution was investigated by means of x-ray diffraction and differential scanning calorimetry. It is found that the alloys exhibit the L21 structure for x⩾0.4. Depending on the Si concentration x, a structural phase transition is found at temperatures between 1000 and 1200K. The transition temperature decreases with increasing Si content x. The magnetic properties were studied using low temperature magnetometry. For x⩾0.4, the magnetization of the compounds is in agreement with a Slater-Pauling-like behavior and with the values obtained from ab initio calculations. For x⩽0.4, enlarged magnetic moments are found due to disorder. The enlarged values are explained by an increase of the Co spin moments and enhanced orbital moments.