Coherence magnetic

Here the generic term Hartmann-Hahn experiment is used for polarization- or coherence-transfer experiments that are based on the Hartmann-Hahn principle (see Section II), that is, on matched effective fields that are created by a rf irradiation scheme. These experiments may be classified according to the following practical and theoretical aspects (see Fig. 6) that are related to properties of samples, spin systems, coherent magnetization transfer, effective Hamiltonians, multiple-pulse sequences, and incoherent magnetization transfer ... 

A serious problem, however, for both paramagnetic and coherent magnetic scattering measurments, at least until higher reflectivity polarizers are available or alternative techniques of polarization analysis are developed, is the low intensity obtained after reflection from the sample as well as from two polarizing crystals. Even for location of apparatus at a high flux reactor, with current techniques the measurement of covalent spin reductions in powder samples can be made as efficiently by profile analysis of a conventional powder diffraction pattern as by polarization analysis. Polarized beam methods including polarization analysis will however, be essential for the determination of form factors. 

Scheinfein MR, Schmidt KE, Heim KR, Hembree GG (1996) Magnetic order in two-dimensional arrays of nanometer-sized snperpaiamagnets. Phys Rev Lett 76 1541-1544 Schmidt H, Ram RJ (2001) Coherent magnetization reversal of nanoparticles with crystal and shape anisotropy. J Appl Phys 89 507-513... 

Since many experimental studies of 7-Fe were performed for 7-Fe particles in a Cu matrix (or Cu alloy, including Cu-Al) [113], [114], it is important to probe the electronic structure of the particle-matrix systems. Embedded-cluster methods are ideally taylored to treat small particles of a metal in a host matrix, a system that would require a very large supercell in band-structure calculations. DV calculations were performed for the 14-atom Fe particle in copper shown in Fig. 21 [118]. Spin-density contour maps were obtained to assess the polarization of the Cu matrix by the coherent magnetic 7-Fe particle. Examples are given in Figs. 22 and 23 for a Fe particle in Cu and 7-Fe in Cu with two substitutional Al. If the matrix is a Cu-Al alloy, this element is known to penetrate the Fe particle [114]. 

Fig. 7.2.31 Filters for homonuclear coherent magnetization transfer. All filters start from and end with longitudinal magnetization, (a) Selective excitation and reconversion of coherences with a nonselective mixing period, (b) Realization of a nonselective mixing period in a z filter via longitudinal magnetization, (c) Nonselective excitation and reconversion of coherences with a selective mixing period, (d) Realization of a selective mixing period by a multi-quantum filter, (e) Selective exchange of transverse magnetization within the multiplets of coupled homonuclear spin pairs by a homonuclear version of the INEPT method.

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