Frequency dependent magnetic susceptibility

Information about the magnetic behaviour of heavy-fermion systems is contained in the wavenumber- and frequency-dependent magnetic susceptibility x q, v). In less strongly correlated metals, x is usually expressed via Stoner s formula [for critical reviews on itinerant magnetism and Stoner theory see, e.g., Moriya (1979), Gautier (1982), Stamp (1985)],... 

Figure G.7. (a) Magnetic noise spectrum of a 1000 1 diluted solution of magnetic protein (horse-spleen ferritin particles) (b) frequency-dependent magnetic susceptibility of the same sample after cycling the temperature at T = 4 K. (Reproduced with permission from Ref. 363.)...

Finally, we note that when band-structure (and wave function) calculations will be available for polymers in the presence of stationary and nonstationary magnetic fields, it will be possible to compute both the current induced by the magnetic field and the static and frequency-dependent magnetic susceptibilities. Since, however, no such calculations for polymers (even in a very approximate form) are available in the... 

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. 

Fannin C. Paul. Wideband measurement and analysis techniques for the determination of the frequency-dependent, complex susceptibility of magnetic fluids. Adv. Chem. Phys. 104 (1998) 181-292. 

Six [Ln(Pc)2] complexes with heavy lanthanide ions (Ln = Tb, Dy, Ho, Er, Tm or Yb) were investigated by the measurements of alternating current (AC) magnetic susceptibility [18]. Out of the six compounds, [TbPc2] and [DyPc2] were found to show temperature and frequency dependence on AC magnetic susceptibility similar to that observed for the transition-metal SMMs, while the rest did not. Their SMM behaviour have been observed either in bulk, in dilute solid solutions... 

FIGURE 3.11 Schematic frequency-dependence diagram of out-of-phase (y") AC susceptibilities measured for the single-molecule magnet Fe8 for a range of frequencies, indicating the slowing down of spin relaxation at low temperatures. 

Because the dielectric properties of each material are different functions of frequency, the A s also depend on frequency. (There will be similar differences-over-sums for magnetic susceptibilities, p,A, /xm, and /xB these are usually small and are neglected in this introductory discussion.)... 

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