Patent ID: 7309617

Claim:
A method for fabricating a reference layer for MRAM memory cells, comprising: providing a layer system for the reference layer, the layer system exclusively consisting of: a first layer of a material having a first Curie temperature, wherein the first layer has a saturation field strength and can be permanently magnetized by an external magnetic field; a second magnetic layer of a material having a second Curie temperature which is significantly lower than the first Curie temperature, wherein the second layer can be magnetized by antiferromagnetic coupling with only the first layer; and a very thin intermediate coupling layer between the first and second layers; forming an artificial antiferromagnet exlusively from the first layer, the second layer and the intermediate coupling layer by the steps of: generating an external magnetic field having a field strength; cooling the layer system from a temperature above the first Curie temperature to below the first Curie temperature by action of the external magnetic field, the field strength of the external magnetic field being greater than the saturation field strength of the first layer, so that magnetization of the first layer is oriented by a second-order phase transition along the field direction of the external magnetic field; and subsequently cooling the layer system below the second Curie temperature, magnetization of the second layer being oriented antiparallel with respect to the magnetization of the first layer on account of antiferromagnetic coupling between the first and second layers, said antiferromagnetic coupling being imparted by the intermediate coupling layer.