US 2009/0268353 A1 · CURRENT-PERPENDICULAR-TO-THE-PLANE (CPP) MAGNETORESISTIVE SENSOR WITH ANTIPARALLEL-FREE LAYER STRUCTURE AND LOW CURRENT-INDUCED NOISE

Abstract

A current-perpendicular-to-the-plane (CPP) magnetoresistive sensor has an antiparallel free (APF) structure as the free layer and a specific direction for the applied bias or sense current. The (APF) structure has a first free ferromagnetic (FL1), a second free ferromagnetic layer (FL2), and an antiparallel (AP) coupling (APC) layer that couples FL1 and FL2 together antiferromagnetically with the result that FL1 and FL2 have substantially antiparallel magnetization directions and rotate together in the presence of a magnetic field. The thickness of FL1 is preferably greater than the spin-diffusion length of the electrons in the FL1 material. The minimum thickness for FL2 is a thickness resulting in a FL2 magnetic moment equivalent to at least 10 Å Ni80Fe20 and preferably to at least 15 Å Ni80Fe20. The CPP sensor operates specifically with the conventional sense current (opposite the electron current) directed from the pinned ferromagnetic layer to the APF structure, which results in suppression of current-induced noise.

Claims27

Dependent claims

A magnetoresistive sensor having electrical leads for connection to a source of sense current and comprising:

one and only one pinned ferromagnetic layer having an in-plane magnetization direction;
an antiparallel free (APF) structure comprising a first free ferromagnetic layer (FL1) having an in-plane magnetization, a second free ferromagnetic layer (FL2) having an in-plane magnetization substantially antiparallel to the magnetization of FL1 and a magnetic moment less than that of FL1, and an AP coupling (APC) layer between and in contact with FL1 and FL2 and consisting essentially of a material selected from the group consisting of Ru, Ir, Rh and alloys thereof, wherein FL2 has a thickness equal to or greater than a thickness that results in a FL2 magnetic moment equivalent to 10 Å Ni80Fe20;
and
an electrically conductive spacer layer between the pinned ferromagnetic layer and FL1 and consisting essentially of an element selected from the group consisting of Cu, Ag and Au;
and wherein the sensor is capable of sensing external magnetic fields when a sense current is applied perpendicular to the planes of the layers in the sensor in a direction from the pinned ferromagnetic layer to the APF structure.

2 more elements

A current-perpendicular-to-the-plane magnetoresistive read head for reading magnetically recorded data from tracks on a magnetic recording medium when a sense current is applied to the head in a direction from a first electrical lead to a second electrical lead, the head comprising:

a substrate;
a first electrical lead layer on the substrate;
one and only one pinned ferromagnetic layer, said one and only one pinned ferromagnetic layer being located on the first electrical lead layer and having an in-plane magnetization direction;
an electrically conductive spacer layer on the pinned ferromagnetic layer and consisting essentially of an element selected from the group consisting of Cu, Ag and Au;
an antiparallel free (APF) structure comprising (a) a first free ferromagnetic layer (FL1) on the spacer layer and having an in-plane magnetization direction, (b) a second free ferromagnetic layer (FL2) having an in-plane magnetization direction substantially antiparallel to the magnetization direction of FL1 and a magnetic moment less than that of FL1, wherein each of FL1 and FL2 is formed of an alloy comprising Fe and one or both of Ni and Co and FL2 has a thickness equal to or greater than a thickness that results in a FL2 magnetic moment equivalent to 10 Å Ni80Fe20, and (c) an AP coupling (APC) layer between and in contact with FL1 and FL2 and consisting essentially of a material selected from the group consisting of Ru, Ir, Rh and alloys thereof;
a second electrical lead layer on FL2;
a ferromagnetic biasing layer for biasing the magnetization of the APF structure, the biasing layer having a magnetization direction substantially antiparallel to the magnetization direction of FL2 in the absence of an external magnetic field;
and
a source of sense current connected to the first and second electrical lead layers and supplying current to the sensor in a direction from the first electrical lead layer through said one and only one pinned ferromagnetic layer, spacer layer, and APF structure to the second electrical lead layer.

6 more elements

Dependencies are inferred from the claim text.

Current-perpendicular-to-the-plane (cpp) magnetoresistive sensor with antiparallel-free layer structure and low current-induced noise

Life of this patent

Current-perpendicular-to-the-plane (cpp) magnetoresistive sensor with antiparallel-free layer structure and low current-induced noise

Life of this patent

Abstract

Claims27