Current-in-Plane Giant Magnetoresistance Sensor Using a Thin Cu Spacer and Dual Nano-Oxide Layers With a ${\rm DR}$ Greater Than $20$ Ohms/sq.

Michael A Seigler

doi:10.1109/tmag.2006.888217

Abstract

The magnetoresistance (MR) of the current-in-plane spin-valve, which is currently utilized as the readback sensor in the majority of hard disk drives, has reached a maximum MR of DR/R min. ~20% and DR sheet ~4 Omega/sq. A new sensor film stack will be introduced here that utilizes a trilayer (CoFe\Cu\CoFe) where the Cu interlayer is very thin (~10 Aring) to enhance the MR and where the Cu thickness is chosen such that the ferromagnetic Neel coupling and the antiferromagnetic Ruderman-Kittel-Kasuya-Yosida (RKKY) coupling between the CoFe layers partially cancel one another, to maximize the sensitivity. By changing the Cu interlayer thickness, the overall interlayer coupling was adjusted from about -0.05 erg/cm 2 to -0.4 erg/cm 2 while keeping the MR large. Nano-oxide layers (NOLs) are also incorporated below and above the trilayer sensor to enhance the MR. An example of this sensor is NiFeCr 20 Aring/CoFeO 10 Aring/CoFe 15 Aring/Cu 10.5 Aring/CoFe 15 Aring/AlO 30 Aring and will be referred to as CIP-3L. With the combination of the thin Cu spacer, the NOLs and minimal additional layers to shunt the current around the trilayer sensor (no antiferromagnetic material and no pinned layers), as deposited sheet films with an MR of DR/R >25% and DR/sq. >20 Omega/sq. were achieved. This paper shows the optimization of the sensor stack, such as film thicknesses, NOL material, and oxidation process, the adjustability of the interlayer exchange coupling between the CoFe layers and also shows the repeatability of the sensor deposition

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