Nanometer-thin L10-MnAl film with B2-CoAl underlayer for high-speed and high-density STT-MRAM: Structure and magnetic properties

The material development of magnetic tunnel junction with a perpendicular easy axis is in great demand to advance spin-transfer torque magnetoresistive random access memory (STT-MRAM) technologies. To realize high-speed and high-density STT-MRAM, a thin-film magnetic material with large perpendicular anisotropy and small spontaneous magnetization has great potential. Here, we develop a thin-film deposition technique for a-few-nanometer-thin L10-MnAl by sputtering and investigate its structure and magnetic properties. Utilization of the B2-CoAl buffer layer allows us to grow L10-MnAl with a large crystalline anisotropy of 8.5 × 105 J/m3, the small spontaneous magnetization of 0.62 T, and the tolerance for 400 °C annealing even at the MnAl thickness of 2 nm. We calculate the device properties based on the obtained material parameters and find that high retention properties, high-speed switching, and low write-error rate can be obtained at the single-digit-nm region, which are not readily achieved by conventional material systems. The results show the potential of L10-MnAl for high-density and high-speed STT-MRAM.