FINE METALLIC PARTICLES FOR MAGNETIC DOMAIN OBSERVATIONS

Fine domain structures of a ferromagnetic specimen can be visualized b y deposition of ultrafine ferromagnetic particles onto its surface. We have applied various ferromagnetic particles, such as Co, Fe, Co-Fe a lloy and Permalloy, to observation of high-density recording states of thin-film recording media. These studies have revealed that single-do main particles mainly contribute to the domain pattern contrast, while very small superparamagnetic particles are so insensitive to the leak age field from the recording media that they deteriorate the image qua lity of the domain patterns, Therefore, suppressing the formation of t he superparamagnetic particles is effective in improving the resolutio n and the image quality of the observed domain patterns. In order to s uppress the formation of superparamagnetic particles, we have attempte d to synthesize hcp-Co particles with large uniaxial anisotropy by all oying Co with some elements which increase the fcc double left right a rrow hcp transformation temperature, but all the Co and Co-alloy parti cles exhibit a pure high-temperature fcc phase.