Quantum tunneling, magnetization

While this generally has only small effects on the static magnetic properties, it may play a relevant role in providing a quantitative agreement with experimental resonance data, and in explaining quantum tunnelling relaxation of the magnetization at low temperature [51]. 

Gatteschi, D. and Sessoli, R. (2003) Quantum tunneling of magnetization and related phenomena in molecular materials. Angew. Chem. Int. Ed., 42,... 

The quantum of magnetic flux is only 2.07 x 10-15 Wb, which is approximately equal to the amount of the earth s magnetic field enclosed by a ring of 10p,m in diameter. The Josephson effect is observed when two superconductors are separated by a very thin insulating layer (about 20 nm). Single electrons and Cooper pairs can tunnel through such a layer. The characteristics of the Josephson junction are now used to define the volt and have enabled the uncertainty in the maintained standard to be reduced to 0.1 p,V. 

Quantum Tunneling between Paramagnetic and Superconducting States of a Nanometer-Scale Superconducting Grain Placed in a Magnetic Field... 

FIGURE 3.12 Magnetization hysteresis of Mni2 at 2.1 K. Note the characteristic steps that are caused by quantum tunneling processes. Redrawn from Ref. 30a. 

Figure 1. Size scale going from macroscopic down to nanoscopic sizes. The unit of this scale is the number of magnetic moments in a magnetic system, roughly corresponding to the number of atoms. The hysteresis loops are typical examples of magnetization reversal via nucieation, propagation, and annihilation of domain walls (left) v a uniform rotation (middle), and via quantum tunneling (right).

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