Insertion under read shield for improved read gap actuation in dynamic flying height
A read/write head is disclosed wherein a non-magnetic layer made of a metal is inserted in the read head on a side opposite to the S1 shield with respect to the sensor. The non-magnetic layer is preferably Cu and is recessed from the ABS to prevent corrosion. A preferred design has a 1 to 5 micron thick non-magnetic insertion layer that extends a distance of 3 to 100 microns along a plane that is perpendicular to the ABS. RG efficiency is enhanced significantly and RG gamma ratio is improved to 1.0 so that a smaller difference in RG, WG, and min-fly point can be achieved at touchdown detection and in normal read/write operations. These results lead to an optimal dynamic performance for a given spacing target and enhanced read gap protrusion at a given heater power. S1/S2A thickness can be independently optimized for magnetic performance consideration only.
1. A magnetic head comprised of a read head structure formed on a substrate and an overlying write head including a heating element formed on an opposite side of the read head structure with respect to the substrate, said read head structure comprises:
(a) an insulation layer having a top surface and formed on the substrate, and with a side adjoining an air bearing surface (ABS);
(b) a non-magnetic insertion layer formed in the insulation layer, said non-magnetic insertion layer is a metal or alloy and is recessed a certain distance from the ABS and has a top surface that is coplanar with the top surface of the insulation layer and contacts an overlying bottom (S1) shield, the non-magnetic insertion layer and other layers in the read head structure and write head expand toward a magnetic medium proximate to the ABS when heat is applied from the heating element wherein the ratio of write head expansion/read head expansion is controlled by a volume of the non-magnetic insertion layer; and
(c) the bottom (S1) shield formed on the non-magnetic insertion layer and on a portion of the insulation layer.
2. The magnetic head of claim 1 wherein said non-magnetic insertion layer has a thickness of about 1 to 5 microns and has a length of about 1 to 100 microns along an axis that is perpendicular to the ABS.
3. The magnetic head of claim 1 wherein the read head structure includes a sensor with a non-magnetic layer that is comprised of a metal in a GMR scheme, or an insulation layer that is alumina or MgO in a TMR design.
4. The magnetic head of claim 1 wherein non-magnetic insertion layer is comprised of Cu or a Cu alloy.
5. The magnetic head of claim 1 wherein said non-magnetic insertion layer is recessed a distance of about 0.3 to 10 microns from the ABS.
6. The magnetic head of claim 1 wherein the non-magnetic insertion layer has a coefficient of thermal expansion (CTE) which is greater than the CTE of alumina.
7. The magnetic head of claim 1 wherein the non-magnetic insertion layer has a thermal conductivity greater than that of alumina to serve as a heat sink.
8. The magnetic head of claim 1 wherein the read head structure is further comprised of a stack of layers in which a gap layer having a sensor element therein adjacent to the ABS, a first upper (S2A) shield, a second insulation layer, and a second upper (S2B) shield are sequentially formed on the S1 shield layer.
9. The magnetic head of claim 8 wherein the upper (S2B) shield also represents a flux return pole in the write head.