Magnetic Relaxation Phenomena

Giitiich et al., Mossbauer Spectroscopy and Transition Metal Chemistry, 

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The magnetic relaxation phenomena can be considered in certain classes magnetic relaxation has been discovered in ferromagnets, spin glass, superparamagnetic particles including SMM... 

Shangda Jiang was born in 1984, received his B.Sc. degree in chemistry at Beijing Normal University in 2006, and he is now a Ph.D. student at Peking University, with Professor Song Gao as his supervisor. His research is focused on the magnetic relaxation phenomena based on lanthanide ions. 

Spinu L, Stancu A (1998) Modelling magnetic relaxation phenomena in fine particles systems with a Preisach-Neel model. J Magnet Magnetic Mater 189 106-114 Srivastava KKP, Jones DH (1988) Toward a microscope description of superparamagnetism. Hyperfine Interactions 42 1047-1050... 

The diffusion coefficient can also be determined from measurements of other phenomena that are controlled by the activated motion of atoms. These indirect methods include internal friction measurements, nuclear magnetic resonance spectra, and some magnetic relaxation phenomena (in ferromagnetic substances). These techniques are advantageous in allowing the measurement of D at lower temperatures than are practicable by the conventional methods. 

As mentioned above, the relaxation phenomena of macromolecules seldom follow the single correlation time theory dictated by eqn (36). In such cases, a wide distribution is usually introduced in the correlation time. However, as discussed elsewhere, the distribution of correlation time not only fails to explain the temperature dependencies of Ti, T2 and the NOE of the non-crystalline components observed by scalar decoupled NMR on linear polyesters and polyethylene, but also overlooks the intrinsic motion of long-chain molecules. On the contrary, the 3r theory dictated by eqn (41) was found to be very effective to describe such temperature dependencies of the relaxation parameters. Irrespectively of whether the motional mode assumed in the 3t model for the C-H vector is really true, the concept that the C-H vector in macromolecules involves plural independent diffusional motions with discretely different correlation times is very useful to explain the magnetic relaxation phenomena of macromolecules, as will be shown later. 

In this section, our recent investigation of LPE by solid-state NMR has been briefly reviewed. Through these studies solid-state NMR has been found to be very useful to studying the crystalline structure of polymers. Although we have been concerned only with LPE of very simple chemical structure, by use of different magnetic relaxation phenomena the developed spectroscopic technique will be applicable to other polymers of complex chemical structure. 

The magnetic relaxation phenomena in lanthanide-containing complexes cover a wide range of magnetic materials, among which the SMMs and single-chain magnets (SCMs) are the two most important families of molecular materials. 

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