THE CONCEPT OF A SINGLE-DOMAIN PARTICLE

All estimations of the 'single-domain' particle size are based on certain approximations which apply to a continuous material, but break down in the limit of discrete atoms. It is shown that when these approximations are eliminated, a very small magnetic particle can never be completely saturated, even though such a state can be a very good approximation to the physical reality. The provious micromagnetic calculations are only approximately valid, which resolves the Brown paradox.