Magnetization and ac susceptibility

To date, bulk measurements like the magnetization and ac-susceptibility have mostly been performed in order to identify a second transition and a reentrant spin-glass (RSG) phase. This low-temperature transition at Tf manifests itself in a number of ways drop of the demagnetization-limited ac susceptibility (fig. 82)... 

To determine the magnetic anisotropy of the clusters we measured dc susceptibility x and ac susceptibility, with components x in phase, and x out-of-phase, as a function of temperature and frequency. (Torres et al., 2002). 

Fig. 2.29. Temperature dependence of the critical fields of -(ET)2l3 obtained from magnetization, specific heat, and ac-susceptibility data. The solid line is a fit to the ac-susceptibility data according to (2.17). The inset shows the temperature dependence of Bc2 obtained from magnetization data close to Tc in an enlarged...

A second transition was detected at 18.5-19 K by the measurement of the magnetization, the AC susceptibility, and the thermal expansion (Franse et al. 1983, Kamma et al. 1983). The transition coincides with the previously reported anomaly... 

An example of such a relaxation process is represented by the transfer of energy between the magnetic spin entity and the lattice vibrations (spin-lattice relaxation). The isothermal, adiabatic and AC susceptibilities are interrelated through (Fig. 2.3)... 

Figure 1.14 Structure of [ 0 3(011)2(0404)2].SHiO (a) and guest-dependent magnetic behaviour (b), showing the DC susceptibility %T product and AC susceptibility (inset) for the virgin hydrated, dehydrated, and rehydrated frameworks. Reprinted with permission from S.O.H. Gutschke, D.J. Price, A.K. Powell and P.T. Wood, Angew. Chem. Int. Ed., 38, 1088. Copyright (1999) Wiley-VCH Verlag GmbH c Co. KGaA.

Fig. 65. Noimalized and background-corrected temperature (left) and field-dependent (right) (1, i, 0) magnetic Bragg intensities (top) and ac susceptibilities (bottom) (Aeppli et al. 1989).

We focus our attention on two measurements, the magnetization under high applied field and the dc and ac susceptibility. 

FIGURE 116 Resistivity of CePtSi2 with a magnetic field up to 0.7 T under 1.7 GPa. Inset (A) Magnetic field dependence of at 1.7 and 1.8 GPa evaluated from resistivity and ac susceptibility, respectively. Inset (B) Temperature dependence of Xx for CePtSij under 1.8 GPa in various magnetic fields (Nakano et al., 2009a). 

Figure 12.29 (a) to (e) The pressure effect on heat capacity and ac susceptibility of the P-phase orystal of p-NPNN. (f) The pressure dependence of magnetic transition temperatures of ferromagnetic p-NPNN and antiferromagnetio TANOL and TVP... 

The low-temperature magnetic and superconducting behavior in the Gd jEr, Rh4B4 system was established by Wang et al. (1978) by means of four-probe electrical resistance and ac-susceptibility techniques see fig. 60. Samples were prepared by arc melting in a Zr-gettered Ar atmosphere and subsequently annealed... 

The structures and dynamic magnetic behaviours of 31-Dy4 and 31-Tb4 have been presented in Figure 3.22. Four lanthanide ions are aggregated in the grid-like metal core by a central p4-S and eight peripheral i2-S atoms from ethanethiol ligands [38]. The individual lanthanide centres occupy distorted six-coordinate [LnNS5] octahedral coordination environments. Ac susceptibilities measurements reveal pronounced temperature dependence with a series of maxima below 28 K, typical for SMM behaviour, in complex 31-Dy4. Furthermore, an... 

Table 10.2 Overview of energy barriers and pre-exponential factors derived from Arrhenius fits of the ac susceptibility data for single-molecule magnets 1-15. 

At high temperatures, a nanoparticle is in a superparamagnetic state with thermal equilibrium properties as described in the previous section. At low temperatures, the magnetic moment is blocked in one potential well with a small probability to overcome the energy barrier, while at intermediate temperatures, where the relaxation time of a spin is comparable to the observation time, dynamical properties can be observed, including magnetic relaxation and a frequency-dependent ac susceptibility. 

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