Rheomagnetic Measurement of Magnetic Recording Particle Concentration And Particle Shape
Original Publication Date: 1986-Jan-01
Included in the Prior Art Database: 2005-Mar-08
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.