PURPOSE: To demonstrate the magnetic domains inside a ferromagnetic material.
DESCRIPTION: This device uses a commercial magnetic domain demonstrator, viewing it with a TV camera. The device uses polarized light to view the magnetization of domains in a ferromagnetic garnet, which has the property of rotating the plane of polarization of the light by an angle dependent on its magnetization. Magnetic domain structure in the garnet is viewed as shown in the photograph. If the magnetic field in which the sample is positioned is increased the domain alignment becomes more complete, and the lines vanish, sometimes leaving a "magnetic bubble," a single small group of domains aligned opposite the surrounding area. Viewing is accommodated using a microscope objective lens on the end of a long tube attached to the TV camera, so that the image is created on the videcon of the camera. The analyzing polaroid, also contained in the tube, is rotated to the correct orientation for optimal viewing.
EQUIPMENT: Mounted magnetic domain demonstrator, TV microscope gizmo, lamp with lens, power supply with polarity switch.
SETUP TIME: 20 min. Note that there is a front side to the magnetic domains apparatus. The front side must be facing the camera otherwise the image of the domains is not clearly visible. See below.
Updated by Jun Qi in 3/13/2000