Effects of induced anisotropy on the bit stability and switching field in magnetic random access memory

One of the features of the new spin-flop switching method with its wide writing window is to use a trilayer synthetic antiferromagnet (SyAF) with circular geometry as the free layer structure. For circular cells with zero in-plane shape anisotropy, the bi-stability of bits is achieved through the formation of induced anisotropy. Both the bi-stability and spin alignment become poor at a small induced anisotropy. On the other hand, a large induced anisotropy has an adverse effect of increasing the switching field. The switching field increase is more pronounced at higher antiferromagnetic exchange coupling of the trilayer SyAF. Our systematic investigations show that the suitable magnitude of induced anisotropy field is in the range 15-20 Oe.