The doping effect of Al_2O_3 on the high-frequency electrical and magnetic properties of CoFeB soft magnetic thin films deposited on Si substrates using RF magnetron sputtering technique

摘要

Soft magnetic thin films have drawn tremendous interests in high-frequency spintronics applications. Here we demonstrate the doping effect of Al_2O_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_2O_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_2O_3, indicating the suppression of eddy current loss in high-frequency application. Moreover, we found that the product of M_s and a which determines the critical switching current density of CoFeB thin films first increases and then decreases with the increasing doping concentration of Al_2O_3. The presented results demonstrated that high doping concentration of Al_2O_3 in CoFeB thin films is beneficial for the high-frequency spintronics applications.