Magnetoresistive sensor with nitrogenated hard bias layer for improved coercivity
View Patent ↗A magnetoresistive sensor having a hard bias structure that provides improved bias field robustness. The sensor includes a nitrogenated hard bias layer and a seed layer that include a nitrogenated NiTa layer and a layer of Ru. The seed layer can also include a layer of CrMn disposed between the layer of NiTa and the layer of Ru. The novel seed structure allows a nitrogenated hard bias layer to be used, while maintaining a high magnetic coercivity of the hard bias layer.
1. A magnetoresistive sensor, comprising:
a sensor stack having a free layer, a pinned layer structure and a non-magnetic layer sandwiched between the free layer and pinned layer structure, the sensor stack having first and second laterally opposed sides;
first and second hard bias structures formed at each side of the sensor stack, each hard bias structure further comprising:
a first seed layer having trace amounts of nitrogen;
a second seed layer comprising Ru formed over the first seed layer; and
a hard magnetic layer formed over the first and second seed layers, the hard magnetic layer including trace amounts of nitrogen.
2. A magnetoresistive sensor as in claim 1 wherein the hard magnetic layer comprises CoPt with trace amounts of nitrogen.
3. A magnetoresistive sensor as in claim 1 wherein the first seed layer has a thickness of 10-30 Angstroms.
4. A magnetoresistive sensor as in claim 1 wherein the second seed layer has a thickness of 3-8 Angstroms.
5. A magnetoresistive sensor as in claim 1 wherein the first seed layer has a thickness of 10-30 Angstroms and the second seed layer has a thickness of 3-8 Angstroms.
6. A magnetoresistive sensor as in claim 1 wherein the first seed layer has been nitrogenated by depositing it in an atmosphere that includes nitrogen, resulting in the first seed layer having a crystal structure with improved in plane orientation.
7. A magnetoresistive sensor as in claim 1 wherein the hard magnetic layer comprises CoPt, and wherein the first seed layer and the hard magnetic layer have been nitrogenated by depositing them in an atmosphere that includes nitrogen, resulting in the first seed layer and the hard magnetic layer each having a crystal structure with improved in plane orientation and improved grain size.
8. A magnetoresistive sensor as in claim 1 further comprising a third seed layer comprising CrMn sandwiched between the first seed layer and the second seed layer.
9. A magnetoresistive sensor as in claim 8 wherein the first seed layer has a thickness of 10-30 Angstroms.
10. A magnetoresistive sensor as in claim 8 wherein the third seed layer has a thickness of 5-20 Angstroms.
11. A magnetoresistive sensor as in claim 8 wherein the second seed layer has a thickness of 3-8 Angstroms.
12. A magnetoresistive sensor as in claim 8 wherein the first seed layer has a thickness of 10-30 Angstroms, third seed layer has a thickness of 5-20 Angstroms and the second seed layer has a thickness of 3-8 Angstroms.
13. A magnetoresistive sensor as in claim 8 wherein the hard magnetic layer comprises CoPt having trace amounts of nitrogen.
14. A magnetoresistive sensor as in claim 8 wherein the hard magnetic layer comprises CoPt having trace amounts of nitrogen, and wherein the first seed layer and the hard magnetic layer are nitrogenated by depositing them in an atmosphere that includes nitrogen, resulting in the first seed layer and the hard magnetic layer each having a crystal structure with improved in plane orientation and improved grain size.
15. A magnetoresistive sensor as in claim 1 further comprising an electrically insulating layer formed between the sensor stack and each of the hard bias structures.
16. A sensor as in claim 1 wherein the first seed layer comprises NiTa.