School of Physics Lecture Demonstration Manual

Eh-4 Magnetic Domains

Published: Tuesday 14 March 2006 - Updated: Tuesday 29 March 2011

Aim

To demonstrate the growth of ferromagnetic domains under the influence of a magnetic field.

Apparatus

Diagrams

Click on pictures to enlarge.

Magnetic Domains Pic

Description

The magnetic domains apparatus consists of a thin (8 microns) transparent crystal of Ferrimagnetic garnet. The material is anisotropic and the Faraday effect (the rotation of the plane of polarisation) is used to make the domain structure visible.When viewed through crossed polaroids the patterns of the domains become visible as adjacent areas of light and dark. The domain apparatus is placed on the microscope object stage and viewed via X100 magnification. A coil of 300 turns comes included with the apparatus and is used to apply a magnetising field. The appearance of the domains under increasing field strength is indicated below. It is also possible to produce magnetic bubbles i.e. very small isolated cylindrical domains. These have been investigated recently for use as memory storage devices due to their stability, yet being able to be formed, moved and destroyed at very high rates. The apparatus is also suitable for the display of these magnetic bubbles.

Safety notes

Electrical safety 

Maintenance 

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