Structural and magnetic properties of Co2FeAl1-xSix.

This work reports about the structural and magnetic properties of the quaternary Heusler alloy Co₂FeAl_1-xSi_x with varying Si concentration. The structure of the Co₂FeAl_1-xSi_x 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 1200 K. 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 [ABSTRACT FROM AUTHOR]