In conventional MRAMs, two ferromagnetic plates, each of which maintains a magnetic field, are separated by a thin insulating layer. Using magnetic fields to change the state of one plate so that it either matches the other plate or has an opposite orientation, bits can be stored. The new approach developed at Tohoku University (Sendai, Japan) instead uses spin currents to switch memory states, allowing perpendicular magnetic domains that are much smaller than conventional MRAMs.
New York University professor Andrew Kent, an expert in mesoscopic magnetic systems, said it was significant that the Japanese researchers used conventional ferromagnetic material.
By crafting magnetic tunnel junctions for perpendicular recording, the researchers group used interfacial anisotropy between the ferromagnetic plates and the tunnel barrier. Using a material with a CoFeB-to-MgO interface allowed the researchers to produce a giant tunnel magnetoresistance ratio that can switch bits on and off with currents as small as 49 microamps.