Читать книгу Introduction to Nanoscience and Nanotechnology - Chris Binns - Страница 25

1 1 Magnetic moment or magnetic dipole moment, denoted by the symbol μ, summarizes the characteristics of a simple loop of current, producing a magnetic field, by the equation μ = IA, where I is the circulating current and A is the area enclosed by the loop. A simple loop such as this produces a dipolar magnetic field similar to that produced by a bar magnet with north and south poles.

2 2 Magnetostatic energy is the energy of a permanent magnet interacting with a static magnetic field.

3 3 A Bohr magneton (1μB) is the magnetic moment of a single free electron produced by its intrinsic angular momentum (spin).

4 4 The high magnetization was first observed in Fe67Co33 alloys, but the magnetically soft variant Fe50Co50 that is used commercially was patented in 1929 by G. W. Elmer.

5 5 Bacterium that infects the lungs of cystic fibrosis sufferers and causes inflammation and breathing problems.

6 6 You should find that your estimate is much larger than the critical size (~100 nm) for a single‐domain particle given in the text. The reason is that the exchange energy in a domain boundary can be reduced by a large factor by spreading it over a number of atomic layers. That is, instead of having an abrupt 180ª reversal of the magnetization across a single atomic plane, the magnetization rotates a fraction of 180° across each plane. This brings the critical size down to ~100 nm.