High-Performance Shape-Anisotropy Magnetic Tunnel Junctions down to 2.3 nm

We show scalability down to 2.3 nm and high performance at single-digit nanometers of shape-anisotropy magnetic tunnel junctions (MTJs) employing a multilayered ferromagnetic structure. We reveal that a free layer with two ferromagnets separated by a MgO layer behaves as a single magnet at small device dimensions owing to magnetostatic coupling in addition to exchange coupling. This nature, in turn, leads to a notable performance increase of the MTJs in the single-digit-nm regime: thermal stability factor Δ of higher than 100 at room temperature; stable switching at temperatures of 150°C or higher; and spin-transfer torque (STT) switching with a dc voltage (intrinsic critical current I _C0 of 8.5 μA) and with a 10-ns pulse below 1.0 V. Also, we find that switching efficiency (Δ/I _C0 ) increases by a factor of three or more as the size decreases. The results show that the shape-anisotropy MTJ provides a route to high-density and high-performance STT-MRAMs in the era of the ultimate scaling.