Low-field magnet

Finally a big advantage of US-based methods is their cheapness when compared to NMR, as well as an easier handling. US probes are usually light and portable, two qualities not shared by the MRI systems, particularly those equipped with cylindrical magnets where the region of interest in often hardly accessible. To partly compensate this, cheaper open C-shaped low-field magnets might be considered since they allow accessibility to external equipments. 

Fig. 2. Temperature dependence of (a) the lattice constants of a La7/8Sri/8Mn03 single crystal (figure taken from Ref. [10]), (b) the resistivity, and (c) the low-field magnetic moment. The cooperative JT transition at Tjt = 269 K results in a doubling of the resistivity and a sharp drop of the magnetic moment (see inset in (c)). Below the temperature TCo = 147 K the crystal goes into a charge-ordered state and the CJT effect vanishes.

Fig. 7. Temperature dependence of the spin-moment 7 around the CJT transition, as derived from the fits of the magnetic moment data with equation (1). The magnetic moment measurements crossing the CJT phase boundary give two corresponding data points, indicated by the solid symbols. The solid line is calculated on the basis of the low-field magnetic moment according to equation (2).

As an alternative method for the determination of the cluster size, we analyzed the low-field magnetic moment data from Fig. 2(c) by means of the modified susceptibility formula [24], derived from equation (1) in the low-field limit g B kB(T — Tc) ... 

FIGURE 35 The low field magnetization curve of GdBigSis with the field applied in-plane at 1.8 K. The dotted lines are guides to the eye (Mori, 2005a). 

Figure 2. Temperatures of martensitic (Tm) and ferromagnetic (Tc) phase transitions determined from DSC and low-field magnetization measurements, as a function of Ni excess x in the studied Nig+zMni-zGa alloys.

Initial (low field) magnetic susceptibility (x) A measure of how easily a material can be magnetized, i.e., reflecting how much iron-bearing minerals there is in a sample. 

Figure 4c reports the 200MHz H- NMR spectrum of fraction 34. It can be seen that the signal-to-noise ratio is acceptable and this demonstrates that offline SEC-NMR can be performed using medium-low field magnets (200MHz), a very attractive feature indeed ... 

Fig. 2.42 The temperature dependence of low-field magnetization B = mT) for double-layer structures EuS(201 ML) - PbS(152 ML) on KCl(lOO) substrate open squares) and LuS(203 ML) -PbS(161 ML) on BaF2(lll) substrate (full circles) [70]...

Fig. 2.43 The temperature dependence of low-field magnetization (B = mT) for three multilayer structures LuS-PbS on Bap2 substrate. Circles correspond to LuS(3 ML) - PbS(50 ML), triangles to LuS(4 ML) - PbS(51 ML) and squares to LuS(16 ML) - PbS(51 ML). The arrows point on the ferromagnetic phase transition temperature Tc determined as inflection point of M T) curve [70]...

These results are in very good agreement with the low-field magnetization curves (Fig. 1) and denote that pentanol-based samples are practically free of agglomerates [8, 15, 19], even at high volumic concentration of magnetic nanoparticles (hydrodynamic volume fraction approximately 0.6), while the less concentrated water-based samples have an important fraction of preformed and field-induced agglomerates. 

Fig. 82. Low-field magnetic structures of PiGa at 1.8 K note the successive spin-flip and spin-slip behaviours...

Fig. 31. Low-field magnetization vs temperature for (Lao.45Ndo.55)o.7Cao.3Mn03 with t > tc after [114a]...

Magnetization curves for nearly stoichiometric TmSe at 1.4 K as a function of field strength and applied pressures are shown in Fig. 180a to c, p. 354. The extrapolated value where the step disappears is about 20 kbar for all three orientations and it was concluded that transitions III and IV disappear. The temperature of the maximum in the low field magnetization at - 3 K (boundary I) increases with increasing pressures (—0.1 K/kbar) and the maximum flattens for the [111] direction and fields up to 7.3 kbar, Missell etal. [4, pp. 280/1]. For the pressure dependence of a at fields along [100] and 1.4 K, also see Guertin et al. [3]. 

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