Magnetic sensor having a Ru/Si based seedlayer providing improved free layer biasing
View Patent ↗A magnetoresistive sensor having a novel seed layer that allows a bias layer formed there over to have exceptional hard magnetic properties when deposited over a crystalline structure such as an AFM layer in a partial mill sensor design. The seed layer structure includes alternating layers of Ru and Si and a layer of CrMo formed thereover. The seed layer interrupts the epitaxial growth of an underlying crystalline structure, allowing a hard magnetic material formed over the seed layer to have a desired grain structure that is different from that of the underlying crystalline layer. The seed layer is also resistant to corrosion, providing improved sense current conduction to the sensor.
1. A magnetoresistive sensor, comprising:
a sensor stack having first and second laterally opposed sides defining an active area, and having first and second laterally extending portions that extend beyond the active area of the sensor, the laterally extending portions each having a crystalline structure and having a surface;
a seed layer formed over the surface of each laterally extending portion, the seed layer comprising:
a plurality of layers comprising Ru;
a plurality of layers comprising Si, the layers comprising Ru and Si being arranged in an alternating fashion with respect to one another; and
a layer of CrMo disposed over the alternating layers comprising Ru and Si; and
first and second hard magnetic layers formed on the seed layer over each of the first and second laterally extending portions;
wherein the layer comprising CrMo has a thickness of 40 to 60 Angstroms.
2. A magnetoresistive sensor, comprising:
a sensor stack having first and second laterally opposed sides defining an active area, and having first and second laterally extending portions that extend beyond the active area of the sensor, the laterally extending portions each having a crystalline structure and having a surface;
a seed layer formed over the surface of each laterally extending portion, the seed layer comprising:
a plurality of layers comprising Ru;
a plurality of layers comprising Si, the layers comprising Ru and Si being arranged in an alternating fashion with respect to one another; and
a layer of CrMo disposed over the alternating layers comprising Ru and Si; and
first and second hard magnetic layers formed on the seed layer over each of the first and second laterally extending portions;
wherein the layer comprising CrMo has a thickness of about 50 Angstroms.
3. A magnetoresistive sensor, comprising:
a sensor stack having first and second laterally opposed sides defining an active area, and having first and second laterally extending portions that extend beyond the active area of the sensor, the laterally extending portions each having a crystalline structure and having a surface;
a seed layer formed over the surface of each laterally extending portion, the seed layer comprising:
a plurality of layers comprising Ru;
a plurality of layers comprising Si, the layers comprising Ru and Si being arranged in an alternating fashion with respect to one another; and
a layer of CrMo disposed over the alternating layers comprising Ru and Si; and
first and second hard magnetic layers formed on the seed layer over each of the first and second laterally extending portions;
wherein the layer comprising CrMo has 10 to 30 atomic percent Mo.
4. A magnctorcsistivc sensor, comprising:
a sensor stack having first and second laterally opposed sides defining an active area, and having first and second laterally extending portions that extend beyond the active area of the sensor, the laterally extending portions each having a crystalline structure and having a surface;
a seed layer formed over the surface of each laterally extending portion, the seed layer comprising:
a plurality of layers comprising Ru;
a plurality of layers comprising Si, the layers comprising Ru and Si being arranged in an alternating fashion with respect to one another; and
a layer of CrMo disposed over the alternating layers comprising Ru and Si; and
first and second hard magnetic layers formed on the seed layer over each of the first and second laterally extending portions;
wherein the layer comprising CrMo has about 20 atomic percent Mo.