Magnetization reversal

Cobalt—chromium films (20 at. % Cr) exhibiting strong perpendicular anisotropy, ie, hexagonal i -axis normal to the substrate surface, have been studied (53). Fifty nanometer films are composed of columnar crystaUites and the domain size was found to be a few stmctural columns in diameter. Magnetization reversal was shown to occur by domain rotation in thick films. Thinner (ca 10-nm thick) films do not show the columnar crystaUite... 

Not all the molecular symmetries are equally suited for favouring a SIM behaviour. Cubic Oh symmetry, for example, in the case of 8-coordinate complexes, does not have second-order uniaxial anisotropy, E, and this geometry does not favour a large energy barrier for magnetization reversal. 

Figure 8.18 TbPc2-based molecular spin-tronic devices, (a) Graphene nanotransistor with sensitivity at the single-molecule level [39, 256], (b) Scheme of the supramolecular spin valve architecture [217]. (c) Scheme of the carbon nanotube NEMS. The magnetization reversal of a TbPc 2 SIMM from a spin state Jz = +6 to Jz = -6 results in a rotation...

Figure 8.20 TbPc 2 SIM and NEMS based resonator [258]. (a) The magnetization reversal of the Tb3+ ion induced by sweeping the magnetic field parallel to the easy axis of the SMM, resulted in an abrupt increase in the differential conductance through the SW-CNT of NEMS. The switching field depends on the nuclear spin state occupied before magnetization reversal, (b) Elistogram of...

A popular method used to date rocks is the potassium-argon method. Potassium is abundant in rocks such as feldspars, hornblendes, and micas. The K-Ar method has been used to date the Earth and its geologic formations. It has also been applied to determine magnetic reversals that have taken place throughout the Earth s history. Another method used in geologic dating is the rubidium-strontium, Rb-Sr, method. Some of the oldest rocks on Earth have been dated with this method, providing evidence that the Earth is approximately 5 billion years old. The method has also been used to date moon rocks and meteorites. 

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