Magnetic device with improved antiferromagnetically coupling film
View Patent ↗The invention is a magnetic device, i.e., a magnetoresistive sensor or a magnetic tunnel junction device, that has a ferromagnetic structure of two ferromagnetic layers antiferromagnetically coupling together with an improved antiferromagnetically coupling (AFC) film. The AFC film is an alloy of Ru 100-x Fe x where x is between approximately 10 and 60 atomic percent. This AFC film increases the exchange coupling by up to a factor or two and has an hcp crystalline structure making it compatible with Co alloy ferromagnetic layers.
1. A magnetoresistive spin valve sensor comprising:
a substrate;
a fixed ferromagnetic layer formed on the substrate and having its magnetization direction pinned in the absence of an applied magnetic field;
a nonmagnetic metallic electrically conducting spacer layer in contact with the fixed ferromagnetic layer; and
a free ferromagnetic layer in contact with the spacer layer and having its magnetization direction free to rotate relative to the magnetization direction of the fixed ferromagnetic layer; and wherein at least one of the fixed and free ferromagnetic layers comprises first and second ferromagnetic films antiferromagnetically coupled to one another and an antiferromagnetically coupling film located between and in contact with the first and second ferromagnetic films and having a thickness sufficient to couple the first and second ferromagnetic films together with their magnetic moments oriented antiparallel to one another, the antiferromagnetically coupling film being formed of a material consisting essentially of Ru and Fe and having a composition Ru 100-x Fe x wherein x is between approximately 10 and approximately 60 atomic percent.
2. A magnetic tunnel junction device comprising:
a substrate;
a fixed ferromagnetic layer having its magnetization direction fixed in the absence of an applied magnetic field;
an insulating tunnel barrier layer in contact with the fixed ferromagnetic layer; and
a sensing ferromagnetic layer having its magnetization direction free to rotate relative to the magnetization direction of the fixed ferromagnetic layer and in contact with the insulating tunnel barrier layer; and wherein at least one of the fixed and sensing ferromagnetic layers comprises first and second ferromagnetic films antiferromagnetically coupled to one another and an antiferromagnetically coupling film located between and in contact with the first and second ferromagnetic films and having a thickness sufficient to couple the first and second ferromagnetic films together with their magnetic moments oriented antiparallel to one another, the antiferromagnetically coupling film being formed of a material consisting essentially of Ru and Fe and having a composition Ru 100-x Fe x wherein x is between approximately 10 and approximately 60 atomic percent.