Touchdown sensor having a more stable crystal structure for use in hard disk drives
View Patent ↗A method and system for providing a touchdown sensor for use in disk drive is described. The touchdown sensor includes a seed layer, a sensor layer on the seed layer, and a capping layer. The sensor layer includes NiFe. In some embodiments, at least one of the seed layer and the capping layer promote stability and performance of the sensor layer.
1. A touchdown sensor comprising:
a seed layer consisting of Ta;
a sensor layer including Ni on the seed layer, the sensor layer being temperature sensitive and adjoining the seed layer, the sensor layer being configured to determine touchdown based on a change in a temperature of the sensor layer; and
a capping layer on the sensor layer, the capping layer adjoining the sensor layer, consisting of Ta;
wherein at least a portion of at least one of the seed layer and the capping layer is amorphous.
2. The touchdown sensor of claim 1 wherein at least one of the seed layer and the capping layer is a multilayer.
3. The touchdown sensor of claim 1 wherein the sensor layer is Ni 1-x Fe x , where x is at least 0.1 and not more than 0.9.
4. The touchdown sensor of claim 1 wherein x is at least 0.18 and not more than 0.2.
5. The touchdown sensor of claim 1 wherein at least one of the seed layer and the capping layer has a crystal structure including a characteristic grain size, a grain boundary and a crystal structure type that remain substantially unchanged up to at least two hundred degrees Celsius.
6. The touchdown sensor of claim 1 wherein at least one of the seed layer and the capping layer has a characteristic grain size of not more than ten nanometers.
7. The touchdown sensor of claim 1 wherein at least one of the seed layer and the capping layer has a thickness and a characteristic grain size of not more than ten nanometers, and wherein the characteristic grain size is not more than the thickness.
8. The touchdown sensor of claim 1 wherein at least one of the seed layer and the capping layer has a thickness of at least ten and not more than one hundred Angstroms.
9. The touchdown sensor of claim 1 wherein the at least one of the seed layer and the capping layer has a thickness of at least thirty and not more than forty Angstroms.
10. The touchdown sensor of claim 1 wherein at least one of the seed layer and the capping layer is an oxide barrier.
11. The touchdown sensor of claim 1 wherein the touchdown sensor consists of the seed layer, the sensor layer and the capping layer.
12. A touchdown sensor comprising:
a Ta seed layer having a thickness of not more than forty Angstroms;
a sensor layer on the seed layer, the sensor layer including Ni and Fe, the sensor layer including at least eighteen and not more than twenty atomic percent Fe, the sensor layer being temperature sensitive and adjoining the Ta seed layer, the sensor layer being configured to determine touchdown based on a change in a temperature of the sensor layer; and
a Ta capping layer on the sensor layer, the Ta capping layer being not more than forty Angstroms thick, the Ta capping layer adjoining the sensor layer, wherein at least one of the Ta seed layer and the Ta capping layer are amorphous.
13. The touchdown sensor of claim 12 wherein the touchdown sensor consists of the Ta seed layer, the sensor layer and the Ta capping layer.
14. A disk drive comprising:
a slider;
media;
a head residing on the slider and having an air-bearing surface (ABS), the head further including a touchdown sensor proximate to the ABS and residing on an amorphous insulating underlayer, the touchdown sensor including a seed layer consisting of Ta, a sensor layer including Ni on the seed layer, the sensor layer being temperature sensitive and adjoining the seed layer, the sensor layer being configured to determine touchdown based on a change in a temperature of the sensor layer, and a capping layer on the sensor layer, the capping layer adjoining the sensor layer and consisting of Ta;
wherein at least a portion of at least one of the seed layer and the capping layer is amorphous; and
touchdown sensor control circuitry coupled with the touchdown sensor, the touchdown sensor control circuitry for driving a current through the touchdown sensor and converting a signal from the touchdown sensor into an indication of whether touchdown has occurred.
15. The disk drive of claim 14 wherein at least one of the seed layer and the capping layer is a multilayer.
16. The disk drive of claim 14 wherein the sensor layer is Ni 1-x Fe x , where x is at least 0.18 and not more than 0.2.
17. The disk drive of claim 14 wherein at least one of the seed layer and the capping layer has a crystal structure stable up to at least two hundred degrees Celsius.
18. The disk drive of claim 14 wherein at least one of the seed layer and the capping layer has a thickness and a characteristic grain size that is not larger than the thickness.
19. The disk drive of claim 14 wherein at least one of the seed layer and the capping layer has a thickness of at least thirty and not more than forty Angstroms.