Low-temperature magnetic behavior

The 72 ground state of [Fe(CN)g] is split by spin-orbit coupling into an E" ground state and an U excited state at (3/2)g. g-tensor value expressions show significant orbital contribution to the low-temperature magnetic behavior (Table 2). Similarly, the Ti ground state of [M(CN)6] (M = Mn Cr ) splits into an Ai... 

Referring to the short Ru-Ru distance, Gibb et al. considered the problem of the electronic structure from a molecular orbital viewpoint [58]. Such a treatment is a poor approximation in this case since it cannot explain the low temperature magnetic behavior, which mainly results from spin-orbit coupling effects. These ones prevail here as seen in other ruthenium(IV) compounds [57]. 

The most spectacular example of such a directed chemical approach toward quantum magnetism is Cu2Te205Br2, a system with weakly connected Cu2+ tetrahedra, as sketched in Fig. 2a) [39], The magnetic susceptibility data given in Fig. 2b) show a broad maximum at Tmax=30 K and a decrease at low temperatures, a behavior that is consistent with weakly coupled tetrahedra of AF coupled spins. A fit to this temperature dependence gives a typical energy scale for the intra-tetrahedra coupling of J=40 K for this compound. A kink at Tc=14.4 K in the susceptibility marks a transition [32],... 

In conclusion, field dependent single-crystal magnetization, specific-heat and neutron diffraction results are presented. They are compared with theoretical calculations based on the use of symmetry analysis and a phenomenological thermodynamic potential. For the description of the incommensurate magnetic structure of copper metaborate we introduced the modified Lifshits invariant for the case of two two-component order parameters. This invariant is the antisymmetric product of the different order parameters and their spatial derivatives. Our theory describes satisfactorily the main features of the behavior of the copper metaborate spin system under applied external magnetic field for the temperature range 2+20 K. The definition of the nature of the low-temperature magnetic state anomalies observed at temperatures near 1.8 K and 1 K requires further consideration. 

Fig. 12. Temperature dependence of the inverse magnetic susceptibility of YbPtSn. The right-hand inset shows the low-temperature magnetic susceptibility, while the magnetization behavior is presented in the upper inset. From Kaczorowski et al. (1999).

Within the fee RSe series TmSe exhibits quite unique properties, since it shows intermediate-valence behavior (Bucher et al. 1975, Campagna et al. 1974, Launois et al. 1980) in combination with low-temperature magnetic order... 

In the event that the amount of hybridization is too strong for the exchange hamiltonian to be an adequate starting point for a theoretical description of the Kondo-like anomalies in the physical properties, the characteristic temperature is often identified with a spin fluctuation temperature T,f which has the obvious definition Tsf = h/keTsf. In this view, Tjt, rather than Tk, is a boundary which separates high temperature (compared to Tsf) magnetic behavior from low temperature nonmagnetic behavior. 

Hysteresis is an extremely important phenomenon, closely connected with oscillatory behavior, as we shall see in Chapter 4. Hysteresis is familiar to physicists from the study of low-temperature magnetic phenomena, but is less commonly encountered in chemistry. It occurs in cooperative reactions like certain types of adsorption, where occupancy of one site makes a neighboring site easier to occupy. Cooperativity may be viewed as a form of autocatalysis in that the more occupied sites we have, the faster the remaining sites become occupied. 

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... 

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