Magnetoresistive tunnelling junction memory with reference layer sandwiched between two antiferromagnetically coupled ferromagnetic free layers

摘要

Magnetoresistive tunnelling junction memory element consists of a first magnetic system R sandwiched between a ferromagnetic tunnelling junction free layer FL1 and at least one other ferromagnetic free layer FL2. The two or more ferromagnetic free layers are antiferromagnetically coupled. The first magnetic system R consists of a ferromagnetic tunnelling junction reference layer having a fixed magnetic moment and is separated from the ferromagnetic tunnelling junction free layer by a tunnelling barrier B1. The tunnelling barrier B1, the tunnelling junction free layer FL1 and the tunnelling junction reference layer form a magnetoresistive tunnelling junction. The first magnetic system R may be formed from a first pinned layer (Ra, fig 3B) antiferromagnetically coupled to a second pinned layer (Rb, fig 3B). Underlayers UL1 and UL2 may be provided to act as diffusion barriers and seed layers for the stack growth. A cap layer CL1 may also be provided. The large distance r between the ferromagnetic free layers FL1 and FL2 means that a conventional spacer layer is rendered superfluous and the memory element can be scaled down without adverse effects on dipole coupling of the free layers.