Steven Granz

Granular L10 FePt-B and FePt-B-Ag (001) thin films for heat assisted magnetic recording

A comparison was made of FePt-B and FePt-B-Ag thin films having different volume contents of boron, which were RF sputtered with in-situ heating at 425–575 °C onto Si substrates with 20 nm thick (002) MgO. By introducing boron into FePt and varying the sputtering conditions, films with grain sizes ranging from 2.5 to 10 nm were produced. The boron promoted columnar growth, but made ordering more difficult. However, by adding Ag into FePt-B, ordering improved while coercivity increased from 7 to 11 kOe with no significant impact on the microstructure. We obtained films with grain sizes down to 2.5 nm with center-to-center spacing of 3.1 nm. The reduced grain size, columnar microstructure and increase in ordering and coercivity by adding Ag into the FePt-B thin films are favorable for application in heat assisted magnetic recording.

Using Ensemble Waveform Analysis to Compare Heat Assisted Magnetic Recording Characteristics of Modeled and Measured Signals

Ensemble waveform analysis is used to calculate signal to noise ratio (SNR) and other recording characteristics from micromagnetically modeled heat assisted magnetic recording waveforms and waveforms measured at both drive and spin-stand level. Using windowing functions provides the breakdown between transition and remanence SNRs. In addition, channel bit density (CBD) can be extracted from the ensemble waveforms using the di-bit extraction method. Trends in both transition SNR, remanence SNR, and CBD as a function of ambient temperature at constant track width showed good agreement between model and measurement. Both model and drive-level measurement show degradation in SNR at higher ambient temperatures, which may be due to changes in the down-track profile at the track edges compared with track center. CBD as a function of cross-track position is also calculated for both modeling and spin-stand measurements. The CBD widening at high cross-track offset, which is observed at both measurement and model, was directly related to the radius of curvature of the written transitions observed in the model and the thermal profiles used.

Intergranular Exchange Coupling in FePt:X:FePt (

In this study we quantitatively determined the exchange coupling across B, C, SiO_x, Cr and TaO_x segregants by measuring the exchange coupling between two FePt layers separated by segregant layers of varying thickness. Our study indicates that the segregant that provides the best exchange break is TaO_x; whereas, C is the worst and SiO_x, Cr and B are in between. Our data indicates that a segregant intergranular region thicker than 0.8 nm should decouple FePt grains if B, TaO_x, SiO_x, or Cr are used, but with C, a thickness greater than 1 nm is required.

{\rm X}={\rm B}

The areal density capability (ADC) of a magnetic recording disk drive is highly dependent on the application or market segment. In this paper, we define a new areal density metric, which represents what areal density is possible under ideal recording conditions. This proposed areal density metric enables the industry to standardize and compare the ADC of magnetic recording disk drives across various recording technologies independent of market segment. We demonstrate the performance of experimental 2-D magnetic recording and heat assisted magnetic recording technology components measured using the proposed areal density metric.