Keywords:negative spin polarization, STO, GMR
Microwave-assisted magnetic recording (MAMR) is projected to help us overcome the areal density limit of the current perpendicular magnetic recording technology. It relies on the energy assist from ac magnetic field generated from a spin torque oscillator (STO). For the spin injection layer (SIL) of the STO, it has been shown that a negatively spin-polarized material such as Fe1-xCrx can reduce the threshold current needed for the operation of the STO because a large spin-transfer torque (STT) can be achieved close to the parallel state of the two ferromagnetic layers in the STO. However, yet-to-be-answered questions include the role of interfacial spin polarization as opposed to bulk spin polarization and the phase stability of FeCr under annealing process. The choice of buffer material is expected to influence the growth of FeCr film, thus the spin polarization of the FeCr film. In this study, we analyze the effect of the buffer layer, annealing, and FeCr composition on the inverse nature of the magneto-resistance (MR) ratio.