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The image on the left is changing domain patterns of silicon steel according to successively changing magnetic field of +2.4, 0 and -2.4 kA/m.
It is dark-field microscopic image of Colloid A-07-dropped specimen. Changes of triangular shapes and sizes of domains are clearly seen.
Colloids for Domain Observation are stable suspensions of colloidal magnetite particles. They are basically the same thing with magnetic fluids, or ferrofluids. Generally, magnetic fluids are designed to be so stable that even under a strong magnetic field no separation between solid and liquid will occur, however the Colloids for domain observation are designed to have moderate stability.

Our Colloids consist of very fine magnetite, approx. 10 nm, and water or oil. They have outstanding features at the same time, that is, high sensitivity and high stability, or no sedimentation and long life.

Water-based A-05D is used by applying a very small amount (e.g. with Q-tip) on a specimen, letting it dry. Then clear patterns of domain can be observed. The image on the right above is electrolytically polished silicon steel surface A-05D is applied. Water-based A-07 is used by dropping a droplet on a specimen and covering with a cover glass making sure it will not dry. Oil-based L-09 is used the same way as A-07. As it dries about 130 times slower than water, it suits for long-time or high-temperature observation. With A-07 and L-09, microscopic observation of domain wall movement is possible. The image on the right bottom is dark-field microscopic image of soft-magnetic thin film A-07 is dropped and covered by a glass. For all observations, specimens need to be polished to mirror surface.

Colloids for Magnetic Domain Observation

ItemBaseContentsAttaching solvent
A-05DWater50 mlNone
A-07Water50 mlNone
L-09Iso-paraffin oil25 ml50ml

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