Effects of magnetic layer thickness on noise in advanced double-layer metal particle tape

Abstract

A series of advanced metal particle tapes with identical particles but different magnetic coating thicknesses from 300 to 150 nm have been taken through a dc-demagnetization remanent process from positive to negative saturation. Magnetization was achieved with an electromagnetic device, which produced uniform magnetization in the longitudinal direction of the tape. Spectral noise power maps have been generated for the tapes following these demagnetization processes. The thickest tape showed characteristics similar to those of conventional thick tapes, such as video, with demagnetized noise lower than the saturation noise, whereas the thinnest was characteristic of a thin film with demagnetized noise greater than that at saturation. A representation of the experimental measurement process, based on a Landau–Lifshitz–Gilbert model of the medium and a simulation of the “reading” process, generated many of the experimental features. The changes in the noise maps with magnetic coating thickness were attributed to the increased contributions from the free surfaces of the tape as the magnetic coating thickness was reduced.