First-order magnetization processes

Asti G. (1990) First-order magnetic processes, Handbook of Ferromagnetic materials, vol. 5, ed. K.FLJ. Buschow and E.P. Wohlfart, (Amsterdam North-Holland) p. 379. 

FOMP first-order magnetization process field approximation)... 

Just as the NMR signal decays exponentially in the transverse plane, the magnetization also relaxes back to its equilibrium state in an exponential fashion during the time t following the rf pulse. For the longitudinal component (M, ), this occurs as a first-order rate process ... 

In 1996 Stack and co-workers reported an unusual 3 1 (copper 02 stoichiometry) reaction between a mononuclear copper(I) complex of a A-permethylated (lR,2R)-cyclohexanediamine ligand with dioxygen. The end product of this reaction, stable at only low temperatures (X-ray structure at —40 °C) is a discrete, mixed-valence trinuclear copper cluster (1), with two Cu11 and a Cu111 center (Cu-Cu 2.641 and 2.704 A).27 Its spectroscopic and magnetic behavior were also investigated in detail. The relevance of this synthetic complex to the reduction of 02 at the trinuclear active sites of multicopper oxidases4-8 was discussed. Once formed, it exhibits moderate thermal stability, decomposed by a non-first-order process in about 3h at —10 °C. In the presence of trace water, the major isolated product was the bis(/i-hydroxo)dicopper(II) dimer (2). 

Lorentzian line shapes are expected in magnetic resonance spectra whenever the Bloch phenomenological model is applicable, i.e., when the loss of magnetization phase coherence in the xy-plane is a first-order process. As we have seen, a chemical reaction meets this criterion, but so do several other line broadening mechanisms such as averaging of the g- and hyperfine matrix anisotropies through molecular tumbling (rotational diffusion) in solution. 

The domain structure, which appears in MnF2 at the spin-flop transition illustrates a general thermodynamic law of intermediate state formation in the process of first-order phase transitions, induced by a magnetic field, and under the condition that the surface energy of the interface boundary (a > 0) is positive. 

---