Magnetic sensor having a free layer containing a single magnetic domain
View Patent ↗A magnetic sensor includes a spacer having at least a nonmagnetic metal layer inserted between the upper shield layer and the longitudinal bias layers or between the upper shield layer and the longitudinal bias layers plus the magnetoresistive film, the shortest distance between the longitudinal bias layers and the free layer of the magnetoresistive film is set smaller than the shortest distance between the longitudinal bias layers and the upper shield layer, and this arrangement ensures that the amount of magnetic flux entering the magnetoresistive film from the longitudinal bias layers is larger than that absorbed by the upper shield layer, thus realizing a magnetic sensor whose Barkhausen noise is suppressed.
1. A magnetic sensor comprising:
a pair of lower and upper shield layers, which also act as a pair of electrodes;
a magnetoresistive film disposed between the pair of shield layers which is including a free layer, an intermediate layer and a pinned layer;
a pair of longitudinal bias layers disposed at both ends of the magnetoresistive film in a track width direction;
a pair of insulation layers disposed between the pair of longitudinal bias layers and the both ends of the magnetoresistive film in a track width direction; and
a spacer including at least a nonmagnetic metal layer is disposed between the upper shield layer and the pair of longitudinal bias layers, and between the upper shield layer and the magnetoresistive film,
wherein a shortest distance between the longitudinal bias layers and the free layer of the magnetoresistive film is smaller than a shortest distance between the longitudinal bias layers and the upper shield layer.
2. A magnetic sensor according to claim 1 , wherein if a distance between the upper shield layer and the lower shield layer, between which the magnetoresistive film is sandwiched, is taken as a shield-to-shield distance, in a region covering the shield-to-shield distances added to the magnetoresistive film on each side thereof in the track width direction the shortest distance between the longitudinal bias layers and the free layer of the magnetoresistive film is smaller than the shortest distance between the longitudinal bias layers and the upper shield layer.
3. A magnetic sensor according to claim 1 , wherein if a distance between the upper shield layer and the lower shield layer, between which the magnetoresistive film is sandwiched, is taken as a shield-to-shield distance, in a region covering the shield-to-shield distances added to the magnetoresistive film on each side thereof in the track width direction a thickness of the spacer is larger than that of a thinnest portion of the pair of insulating layers disposed between the longitudinal bias layers and the free layer of the magnetoresistive film.
4. A magnetic sensor according to claim 1 , wherein the shortest distance in the track width direction between the longitudinal bias layers and the free layer of the magnetoresistive film is smaller than the shortest distance between the longitudinal bias layers and the upper shield layer in a direction perpendicular to the track width direction.
5. A magnetic sensor according to claim 1 , wherein the shortest distance between the longitudinal bias layers and the upper shield layer is 1.5 or more times the shortest distance in the track width direction between the longitudinal bias layers and the free layer of the magnetoresistive film.
6. A magnetic sensor according to claim 1 , wherein the shortest distance between the longitudinal bias layers and the upper shield layer is 1.8 or more times the shortest distance in the track width direction between the longitudinal bias layers and the free layer of the magnetoresistive film.
7. A magnetic sensor comprising:
a pair of lower and upper shield layers;
a magnetoresistive film disposed between the pair of shield layers and having a laminated structure made up of a free layer, an intermediate layer and a pinned layer; and
a pair of longitudinal bias layers disposed at both ends of the magnetoresistive film in a track width direction;
wherein a sensing current is made to flow in a direction of thickness of the magnetoresistive film, a spacer including at least a nonmagnetic metal layer is disposed between the upper shield layer and the longitudinal bias layers, and a shortest distance between the longitudinal bias layers and the free layer of the magnetoresistive film is smaller than a shortest distance between the longitudinal bias layers and the upper shield layer;
wherein the intermediate layer of the magnetoresistive film is a tunneling barrier layer and a resistivity of the nonmagnetic metal layer forming the spacer is 200 μΩ·cm or less.
8. A magnetic sensor according to claim 1 , wherein the nonmagnetic metal layer is formed of a metal of at least one element selected from a group of Cr, Mo, Ta, Ti, Ni, Nb and W.
9. A magnetic sensor comprising:
a pair of lower and upper shield layers;
a magnetoresistive film disposed between the pair of shield layers and having a laminated structure made up of a free layer, an intermediate layer and a pinned layer; and
a pair of longitudinal bias layers disposed at both ends of the magnetoresistive film in a track width direction;
wherein a sensing current is made to flow in a direction of thickness of the magnetoresistive film, a spacer including at least a nonmagnetic metal layer is disposed between the upper shield layer and the longitudinal bias layers, and a shortest distance between the longitudinal bias layers and the free layer of the magnetoresistive film is smaller than a shortest distance between the longitudinal bias layers and the upper shield layer;
wherein the intermediate layer of the magnetoresistive film is a conductive layer and a resistivity of the nonmagnetic metal layer forming the spacer is 100 μΩ·cm or less.
10. A magnetic sensor according to claim 9 , wherein the nonmagnetic metal layer is formed of a metal of at least one element selected from a group of Cr, Mo, Ta, Ti, Ni, Nb, Au, Cu, Ag, Al, Rh and W.