Demonstration of spin transfer torque (STT) magnetic recording

In the magnetic hard disk drive industry, a continuous increase in the recording density requires higher anisotropy media in order to maintain thermal stability. However, further advances by scaling have run into a stumbling block due to limitations on the required magnetic fields, particularly for writing, which is currently being addressed by alternative approaches such as heat-assisted magnetic recording and microwave-assisted magnetic recording technologies. In this work, we investigate and demonstrate another alternative approach which is based on the effect of the spin transfer torque (STT). The approach uses tunneling spin-polarized currents, instead of magnetic fields, between a nanoscale magnetic probe and a magnetic recording media, both with a perpendicular anisotropy. Writing is performed by spin polarized electrons injected from the probe into the media, due to the STT effect. Reading is produced by the tunneling magnetoresistance (TMR) effect between the two magnetic layers, in the probe writer and the media substrate, respectively. The energy-efficient switching, with an energy of 3.1 MA/cm2, is confirmed through the TMR and the magneto-optical Kerr effect. The demonstrated STT-based magnetic recording overcomes the magnetic field limitations to both writing and reading and thus paves the way for the next-generation energy-efficient and extremely high-density recording.