Magnetic noise studies in advanced metal particle tapes

Abstract

The aim of this research was to achieve two objectives: assembly of magnetisation profiles and noise studies on flexible media. Magnetic profiles of the media were established using anhysteretic techniques derived from Alternating Current (AC) bias analogue recording. The intention of this investigation was to establish processes that could be used to generate non-uniform magnetisation states in tapes, which could be used for spatial analysis of noise sources. In practice, as the project progressed, a rapid decrease in magnetic coating thickness of tapes without a similar reduction in write head gap length prevented this approach and modelling studies were substituted as an alternative.
The second and principal objective of this research was the investigation of remanent magnetic noise as a function of Direct Current Demagnetisation (DCD) and Isothermal Remanent Magnetisation (IRM) processes. These measurements were
based around a reel to reel tester and a Linear Tape-Open (LTO) drive provided by Hewlett-Packard and were made in the range appropriate to data densities and data rates of the LTO generation one system. Data was recorded by capturing the time series using a digital storage scope, and FYI' analysis of the time series was used to obtain the noise power spectra. Noise data was analysed and, in particular, the iniestigation addressed the structure of noise sources in terms of their spatial
distribution in the tape. The majority of the experimental studies were made in terms of noise related to uniform rernanent states of the tapes as these were considered to be related more directly to the media noise without complications of signal
dependent features generated by sharp transitions in magnetic state. However, for completeness and also to start to relate findings to practical applications, some tone noise studies were made towards the end of the study along with dc remanent studies of states generated with a standard write head rather than a magnetiser.