Determination of Transition Jitter Noise by Time Domain Analysis

Transition jitter noise can be caused by a variety of factors such as contributions by the medium, head, and drive electronics. In this work, transition jitter noise in magnetic recording is measured based on the time domain analysis. An example of transition jitter noise in perpendicular media is investigated using captured noisy replay signals compare with a reconstructed ideal signal. It is found that transition noise increased with increasing linear density and dropped sharply after the maximum point.

The Influences of Ru Seed Layer Microstructure on Structural Properties of CoCrPt-SiO2 Perpendicular Media

CoCrPt-SiO2granular film is well known as a perpendicular magnetic recording (PMR) media. To control the segregated structure of the recording layer, the role of the Ru underlayer is important. CoCrPt-SiO2perpendicular recording films were prepared by magnetron sputtering, with a series of Ru films as seed layer. The microstructure of Ru seed layers and their influences on the grain size, roughness and surface morphology of CoCrPt-SiO2granular films were investigated. It was found that the microstructure of seed layer obviously effected the structure and grain isolation of recording layers. The grain size and roughness of CoCrPt-SiO2recording layer were both increased with increasing the thickness of Ru seed layer. It is concluded that the thin and rough Ru seed layer is suitable for high-density magnetic recording media, and Ru seed layer with suitable thickness is very helpful for the achievement of perfect isolation and excellent magnetic properties. The result revealed that it was relatively easy for the CoCrPt grains to get perfect isolation with Ru thickness of 70 nm.

L10-CoPt Bit Patterned Media with Tilted Easy Axis for Ultrahigh Areal Density over 2.5 Tb/in2

Ultrahigh areal density is the key target of hard disk drive technology. Hence, writing field strength from head and switching field, Hsw, of media should be improved. In this work, we propose the one of alternative method to increase data density and reduce Hsw of the media by using tilted easy axis technology for bit patterned media (BPM) at areal density beyond 2.5 Tb/in2. Moreover, transition noise and superparamagnetic limit have been eliminated owing to characteristics of BPM. The effect of exchange coupled between adjacent bits, Adot, of tilted easy axis of BPM is analyzed by micromagnetic simulation software - the object oriented micromagnetic framework based on Landau-Lifshitz-Gilbert equation. The BPM with tilted easy axis perform clearly the reduction of Hsw below perpendicular media and available writing head field. The Adot of BPM has no effect on decreasing Hsw. Anisotropy and Zeeman energy density of BPM with tilted easy axis are higher and lower than perpendicular BPM, respectively. Thereby, BPM with tilted easy axis have high potentiality to improve Hsw of media at ultrahigh data density.