Paper detail

Structural and magnetic properties of Cr-diluted CoFeB

The crystallization process and the magnetization of Cr diluted CoFeB was investigated in both ribbon samples and thin film samples with Cr content up to 30 at. %. A primary crystallization of bcc phase from an amorphous precursor in ribbon samples was observed when the annealing temperature rose to between 421 oC and 456 oC, followed by boron segregation at temperatures between 518 oC and 573 oC. The two onset crystallization temperatures showed strong dependences on both Cr and B concentrations. The impact of Cr concentration on the magnetic properties including a reduced saturation magnetization and an enhanced coercive field was also observed. The magnetizations of both ribbon samples and thin film samples were well fitted using the generalized Slater-Pauling curve with modified moments for B (-0.94 μB) and Cr (-3.6 μB). Possible origins of the enhanced coercive field were also discussed. We also achieved a damping parameter in CoFeCrB thin films at the same level as Co40Fe40B20, much lower than the value reported for CoFeCrB films previously. The results suggest a possible advantage of CoFeCrB in reducing the critical switching current density in Spin Transfer Torque Random Access Memory (STT-RAM).