Thin-film magnetic device with strong spin polarization perpendicular to the plane of the layers, magnetic tunnel junction and spin valve using such a device

A thin-film magnetic device comprising a substrate, a composite assembly deposited by cathode sputtering comprising:

• a first magnetic layer made of a material with a positive effective anisotropy, the magnetization of which is oriented perpendicular to the plane of said layer and the positive effective anisotropy per unit of surface area k2 including bulk and interfacial contributions is [(kv2−2πM22)e2+ks2] where:
• kv is a volume anisotropy of the first magnetic layer;
• M is the magnetization of the first magnetic layer;
• e2 is the thickness of the first magnetic layer;
• and
• ks2 is the interfacial anisotropy of the first magnetic layer;
• a second magnetic layer made of a material with a negative effective anisotropy, the negative effective k3 anisotropy per unit of surface area k3 including bulk density and interfacial contributions is [(kv3−2πM23)e3+ks3] where:
• kv3 is a volume anisotropy of the second magnetic layer;
• M is the magnetization of the second magnetic layer;
• e3 is the thickness of the second magnetic layer;
• and
• ks3 is the interfacial anisotropy of the second magnetic layer;
• said second magnetic layer having a spin polarization of at least 50%, wherein the second magnetic layer spin polarizes electrons traversing through the second magnetic layer when an electrical current flows perpendicular to the plane of the second magnetic layer;
• and
• a third non-magnetic layer, in direct contact with the second magnetic layer on its interface opposite to the interface with the first magnetic layer and made of a material that is not depolarizing for electrons passing through the third non-magnetic layer,
• wherein a coupling energy per unit of surface area between the first magnetic layer and the second magnetic layer is at least twice the absolute value of the effective negative anisotropy per unit of surface area of the second magnetic layer, and the sum of the effective magnetic anisotropy values k2+k3 is positive, and
• wherein the first magnetic layer is anchored and said device comprises means of causing an electric current to flow through its layers in a direction substantially perpendicular to the plane of said layers.