Spin Fluctuations In Systems Research Articles

Band magnetism due to f-electrons

Abstract Specific heat data illustrate several types of itinerant or band magnetism in actinide intermetallic compounds. The results show ferromagnetic spin fluctuations in U Al2 with Tsf = 25 K, itinerant-electron antiferromagnetism in NpSn3 with TN = 9.5 K,and itinerant-electron ferromagnetism in NpOs2 with Tc = 7.9 K. Specific heat studies of dilute U1-xTh xAl2 show the theoretically predicted modifications due to impurity scattering in a spin fluctuation system. For NpSn3 it is possible to show the b.c.s. nature of the transition due to the gap formation.

Magnetic resonance and related studies in cerium‐tin alloy

AbstractThe results of nuclear magnetic resonance (NMR) and magnetic susceptibility measurements in CeSn3 are presented together with other available data. The magnetic susceptibility of CeSn3 shows a broad maximum around 135 K and a rapid rise below 30 K. The 119Sn Knight shift in CeSn3 in the temperature region 1.2 t o 300 K is not proportional to the bulk susceptibility. The electrical resistivity of CeSn3 shows a T2 term at low temperatures as expected in localised spin fluctuation systems, and the coefficient of the electronic specific heat is also very large. These results suggest sizeable 4f occupation near the Fermi level in CeSn3.

Transport properties of local spin fluctuation systems

The dynamical susceptibility due to local spin fluctuations in transition metals has been calculated in RPA, employing a generalized Wolff model with different Coulomb interactions at host and impurity sites, modified hopping from or into the impurity sites, and including potential scattering. The electrical and thermal resistivities and the diffusion part of the thermopower have been calculated, assuming well-localized spin fluctuations. The results for resistivity and thermopower turn out to be surprisingly similar to those obtained for Kondo systems. In particular, a giant peak in the thermopower is found which is of the same magnitude and of similar shape in both systems. The deviations from the Wiedmann-Franz law are also strongly temperature dependent, with a maximum of about 16% near the spin fluctuation temperature.

Theory of neutron scattering on local spin fluctuation systems

The cross section for inelastic neutron scattering on local spin fluctuations in dilute alloys likeA1Mn is calculated in the framework of a semiphenomenological theory. It is found that resonance scattering of the conduction electrons strongly enhances the spin fluctuations near (and at) the impurity sites, leading to a peak in the equal-time spin correlation function, the width of which is determined by the spin fluctuation temperature.

Long-range correlations in local spin fluctuation systems

Long-range spin correlations similar to those predicted in Kondo systems are also found to exist in local spin fluctuation systems like Al Mn, but are negligibly small in systems like Pd Ni.