Michael Allen Seigler

Heat-Assisted Magnetic Recording

Due to the limits of conventional perpendicular magnetic recording, it appears that alternative technologies are needed at areal densities >500 Gb/in2. Heat-assisted magnetic recording (HAMR) is a promising approach to extend areal densities to 1 Tb/in2 and beyond. All of the unique components necessary for a working HAMR system have been demonstrated. Although HAMR permits writing on high Hc media with lower magnetic fields and can produce higher write gradients than conventional magnetic recording, head/media spacing and the development of high Hc media with small grains remains challenging

Integrated Heat Assisted Magnetic Recording Head: Design and Recording Demonstration

Scaling the areal density, while maintaining a proper balance between media signal-to-noise ratio, thermal stability, and writability, will soon require an alternative recording technology. Heat assisted magnetic recording (HAMR) can achieve this balance by allowing high anisotropy media to be written by heating the media during the writing process (e.g., by laser light) to temporarily lower the anisotropy. Three major challenges of designing a HAMR head that tightly focuses light and collocates it with the magnetic field are discussed: 1) magnetic field delivery; 2) optical delivery; and 3) magnetic and optical field delivery integration. Thousands of these HAMR heads were built into sliders and head-gimbal assemblies, and optical and scanning electron micrograph images are shown. Scanning near-field optical microscopy (SNOM) characterization of the HAMR head shows that the predicted ~ lambda/4 full-width half-maximum (FWHM) spot size can be achieved using 488 nm light (124 nm was achieved). SNOM images also show that wafer level fabricated apertures were able to effectively eliminate sidelobes from the focused spot intensity profile. A magnetic force microscopy image of HAMR media shows that non-HAMR (laser power off) was not able to write transitions in the HAMR specific media even at very high write currents, but transitions could be written using HAMR (laser power on), even at lower write currents. A cross-track profile is shown for a fully integrated HAMR head where the magnetic pole physical width is ~350 nm, but the written track is ~200 nm, which demonstrates HAMR. A HAMR optimization contour shows that there is an optimum write current and laser power and that simply going to the highest write current and laser power does not lead to the best recording. Lastly, some prospects for advancing HAMR are given and a few key problems to be solved are mentioned.

Current-in-Plane GMR Trilayer Head Design for Hard-Disk Drives: Characterization and Extendibility

The current-in-plane giant magnetoresistive (GMR) trilayer readback sensor (CIP-3L), where only one permanent magnet at the back edge of the GMR stack is used to stabilize and bias a dual free layer system, is reviewed. Micromagnetic modeling is employed to show that the design has improved efficiency over abutted junction (ABJ) tunneling magnetoresistive (TMR) head designs. An experimental evaluation of how permanent magnet thickness (PM Th), interlayer exchange coupling (J), and stripe height impact the signal-to-noise ratio, symmetry, and stability of prototype CIP-3L heads is conducted. The study indicates that PM Th >400 nm, J<-0.8 erg/cm2, and a read width to SH aspect ratio of 1:1 to 0.75:1, gives optimal transfer curve performance. A head gimbal assembly spinstand comparison on perpendicular recording media with best-in-class TMR readers shows that although the amplitude of the CIP-3L heads is lower (believed to be process related), the symmetry, stability, and most important, bit-error rate normalized to electrical write width and read width, are comparable. In addition, the CIP-3L design shows better linearity and low-frequency noise performance than TMR heads. The areal density performance of the best CIP-3L heads shows 195 Gb/in2 recording capability and linear densities of 1100 kbpi

Exchange tab stabilized readback transducers for areal densities exceeding 20 Gb/in/sup 2/

We present results from a high-density giant magnetoresistive magnetic recording reader using exchange bias stabilization. This novel reader design approach reduces the amount of parasitic resistance, as the sense current is not delivered through high resistivity permanent magnets. Heads were demonstrated to deliver areal densities in excess of 24 Gb/inch/sup 2/. The electrical performance of these heads, in particular, amplitude sensitivity, microtrack profiles and areal density capability are presented. Reader film properties and manufacturability of this approach are discussed in detail.

Current-perpendicular-to-plane multilayer sensors for magnetic recording

We investigated current-perpendicular-to-plane giant magnetoresistance multilayer (CPP-ML) sensors with an active region of (1.0-nm CoFe/1.8-nm Cu) /spl times/ 15 nm. These sensors would allow a shield-to-shield spacing of less than 50 nm. Square CPP-ML devices ranging in size from 120 to 365 nm on a side have been fabricated and tested. In this paper, we focus on the magnetotransport properties of the 140 nm devices, which were measured at room temperature. The average device characteristics were found to be R/sub max/=1.0 /spl Omega/, R/sub min/=0.81 /spl Omega/, DR=191.1 /spl Omega/, and DR/R/sub min/=23.7. These values were measured by using a four-point probe geometry; the data were not corrected for lead or contact resistance and no current crowding was observed. After correction for buffer and seed layer resistances, the magnetoresistance had an intrinsic DR/R/sub min/ value of 55.6%. Our measured results are in good agreement with values obtained with a simple two-current series resistance model. We demonstrate that our CPP-ML structures are viable candidates to replace current-in-plane spin valves as the next generation magnetic recording readback sensor.

Current-in-Plane Giant Magnetoresistance Sensor Using a Thin Cu Spacer and Dual Nano-Oxide Layers With a

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/Rmin.~20% and DRsheet~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/cm2 to -0.4 erg/cm2 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

{\rm DR}

A spinvalve using a permanent magnet as the pinned layer in a synthetic antiferromagnet of a spinvalve is described here. Permanent magnet materials can have the following advantages over antiferromagnetic materials: superior corrosion resistance, a large switching field even at relatively high temperatures, and not needing a high temperature anneal to set its magnetic orientation. The giant magnetoresistance, high field switching, and switching at high temperatures was investigated for various spinvalves using the following film stacks as the pinned layer: CoCrPt (CCP); CCP\CoFe, CCP\Ru\CoFe; and CCP\CoFe\Ru\CoFe. It was found that a thin CoFe layer between the CCP and Cu and between the CCP and Ru enhances giant magnetoresistance and antiferromagnetic coupling, respectively. When the CCP is used in a synthetic antiferromagnet, the CCP coercivity increases compared to a single layer of CCP. The switching field of CCP at 425 °C is >1000 Oe, at the same temperature the switching field for an antiferromagne...

Greater Than

Heat-assisted magnetic recording (HAMR), also known as hybrid recording, is one of the technologies proposed for extending hard disk drive areal densities beyond a Tb/in2. Due to their planar nature and compatibility with existing hard disk drive head fabrication techniques, dielectric optical waveguides have been suggested as a means for delivering light directly to the recording medium or near field optical transducer. In this paper we present spin stand experimental results from a dielectric optical slab waveguide fabricated on an AlTiC slider.

20

Scaling the areal density, while maintaining a proper balance between media signal-to-noise, thermal stability and writability will soon require an alternative recording technology. Heat Assisted Magnetic Recording (HAMR) can achieve this balance by allowing high anisotropy media to be written by heating the media during the writing process (e.g. by laser light) to temporarily lower the anisotropy. Three major challenges of designing a HAMR head that tightly focuses light and collocates it with the magnetic field are discussed: 1) Magnetic Field Delivery, 2)Optical Delivery, and 3) Integration of Magnetic & Optical Field Delivery Components. Thousands of these HAMR heads were built into sliders and HGAs, and optical and scanning electron micrograph images are shown. Scanning near-field optical microscopy (SNOM) characterization of the HAMR head shows that the predicted ~λ/4 full-width half-maximum (FWHM) spot size can be achieved using 488 nm light (124 nm was achieved). SNOM images also show that wafer level fabricated apertures were able to effectively eliminate sidelobes from the focused spot intensity profile. An MFM image of HAMR media shows that Non-HAMR (laser power off) was not able to write transitions in the HAMR specific media even at very high write currents, but transitions could be written using HAMR (laser power on), even at lower write currents. A cross-track profile is shown for a fully integrated HAMR head where the magnetic pole physical width is ~350 nm, but the written track is ~200nm, which demonstrates HAMR. A HAMR optimization contour shows that there is an optimum write current and laser power and that simply going to the highest write current and laser power does not lead to the best recording. Lastly, some prospects for advancing HAMR are given and a few key problems to be solved are mentioned.

Ohms/sq.

In this paper we show the feasibility to integrate waveguide optics into magnetic recording sliders using current recording head manufacturing techniques. Thin film planar waveguides were deposited on ceramic substrates and structured to yield rectangular waveguides positioned on the front face of recording sliders that fly at 20 nm spacing over a glass disk. The thin film waveguide is equipped with a diffraction grating that allows light to be coupled into the waveguide and directed towards the air bearing surface. Optical properties of selected waveguide stacks are presented together with photographs of etched waveguide structures on AlTiC sliders.