誘導スピンフロップモードを用いたtoggle MRAM の書き込み磁場の低減及び書き込みマージンの増大

抄録

Free layer structures, where two soft magnetic layers were ferromagnetically coupled with a synthetic antiferromagnet (SAF) through non-magnetic layers, were demonstrated to freely control the spin-flop field ( H_flop) and the saturation field ( H_s) of 0.32-μm-wide magnetic tunnel junctions in toggle magnetoresistive random access memories (MRAMs). In the free layer, by reducing the coupling strength through the non-magnetic layers, the magnetization reversal of each soft magnetic layer induced a spin flop of the SAF at a lower field (called the “induced spin-flop mode” ), resulting in an H_flop reduction. The H_swas significantly increased while maintaining a low H_flop by replacing the bilayer SAF with a multilayer SAF. The free layers using the induced spin-flop mode are expected to reduce the write field of toggle MRAMs with densities greater than 4 Mb to less than 50 Oe.