Willem Frederik Druyvesteyn

Magnetoresistance in laminated NiFe films

A new way of detecting very small magnetic fields is presented, using the magnetoresistance effect of laminated permalloy. The magnetic properties of permalloy/molybdenum/permalloy sandwiches are investigated. It was found that for molybdenum layers above ca. 1000 A the effect of lamination decreases. Model calculations about the magnetic structures are presented. The calculated results agree with the experimental results.

Analysis of a method for measuring the magnetocrystalline anisotropy of bubble materials

A method of measuring the uniaxial anisotropy of bubble materials is analyzed. The method consists of observing the in‐plane field H∥* at which a stripe domain pattern disappears. Calculations, based on a model with uniaxial anisotropy, are presented which give a relation between H∥* and the uniaxial anisotropy field HK for different values of the characteristic magnetic length. It is shown that H∥* is always smaller than HK owing to the influence of the wall energy and the demagnetizing energy. The calculations are verified experimentally.

Magnetic behaviour of narrow track thin‐film heads

The influence of the trackwidth on the performance of thin film heads has been tested. Results of experiments on the wafer have indicated an increase in the head efficiency with decreasing trackwidth. This was underlined by measurements of the head fringe field and tape recording experiments. A model which takes the domain structure into account has been developed to interpret this behaviour.

Thickness and magnetization variation in magnetic bubble materials

Local variations in thickness or in magnetization of magnetic bubble films give rise to changes in the bubble radius and to translational forces. The translational forces are calculated for several cases of thickness and magnetization variations. Situations where the variations in thickness or magnetization extend over a small region (of the order of the bubble radius) are considered, as well as situations where these variations extend over a much larger region. The influence of magnetization variations on the bubble radius is more than a factor of 2 stronger than the influence of thickness

A special kind of magnetic domain: Hollow bubble with at its centre a bubble

Abstract Experiments and calculations are reported on a cylindrical magnetic domain structure consisting of a hollow bubble with a bubble at its centre.