The doping effect of Al 2 O 3 on the high-frequency electrical and magnetic properties of CoFeB soft magnetic thin films deposited on Si substrates using RF magnetron sputtering technique

Soft magnetic thin films have drawn tremendous interests in high-frequency spintronics applications. Here we demonstrate the doping effect of Al 2 O 3 on the high-frequency electrical and magnetic properties of CoFeB soft magnetic thin films by systematically investigating the dependences of exchange constant A , saturation magnetization M s and damping constant α on the Al 2 O 3 doping concentration. In contrast to the decreased exchange constant due to the non-magnetic doping, the electrical resistivity of CoFeB thin films is found to be increased by the doping of Al 2 O 3 , indicating the suppression of eddy current loss in high-frequency application. Moreover, we found that the product of M s and α which determines the critical switching current density of CoFeB thin films first increases and then decreases with the increasing doping concentration of Al 2 O 3 . The presented results demonstrated that high doping concentration of Al 2 O 3 in CoFeB thin films is beneficial for the high-frequency spintronics applications.