Browse Prior Art Database

Rheomagnetic Measurement of Magnetic Recording Particle Concentration And Particle Shape

IP.com Disclosure Number: IPCOM000059849D
Original Publication Date: 1986-Jan-01
Included in the Prior Art Database: 2005-Mar-08
Document File: 1 page(s) / 9K

Publishing Venue

IBM

Related People

Karis, TE: AUTHOR

Abstract

Flow of magnetic recording ink through an orifice orients acicular magnetic particles parallel to the flow field just downst from the constriction, much as logs on the river floating into a narrows all begin to point downstream. The net orientation of the particles depends on their size, shape, and the flow rate for a given fluid viscosity and flow geometry. For ferromagnetic particles with shape anisotropy, the initial susceptibility, hence the magnetic moment, decreases with increasing alignment of the particles parallel to the magnetic field of a coil wound around the tube downstream from the constriction. Consequently, the measured small-signal rf inductance of the coil reflects both the concentration and bulk alignment of the particles in the coil.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 69% of the total text.

Page 1 of 1

Rheomagnetic Measurement of Magnetic Recording Particle Concentration And Particle Shape

Flow of magnetic recording ink through an orifice orients acicular magnetic particles parallel to the flow field just downst from the constriction, much as logs on the river floating into a narrows all begin to point downstream. The net orientation of the particles depends on their size, shape, and the flow rate for a given fluid viscosity and flow geometry. For ferromagnetic particles with shape anisotropy, the initial susceptibility, hence the magnetic moment, decreases with increasing alignment of the particles parallel to the magnetic field of a coil wound around the tube downstream from the constriction. Consequently, the measured small-signal rf inductance of the coil reflects both the concentration and bulk alignment of the particles in the coil. Since the degree of alignment at a given set of conditions decreases with decreasing acicularity, the inductance at a given flow rate increases with decreasing particle aspect ratio.

Extensive testing done with a typical magnetic recording ink produced the following results. A quantity referred to as the reduced inductance L* = L' - L was defined, with L' being the inductance at zero flow rate, and L the inductance of flow rate Q. The reduced inductance was adequately fit by an empirical relation L* = A + B log(Q), where A and B are positive coefficients obtained from a least squares regression. Parameter A was demonstrated to...