Spin fluctuations and properties of the thermoelectric power of nearly ferromagnetic iron monosilicide

A fluctuation mechanism of electron transitions in magnetic semiconductors

“…and summing up the diagram series in the approximation of uniform local fields [3], we get, by analogy with [2,4], that…”

“…The quantities associated with electron scattering by the random ξ -and η -fields can be found using the relations similar to those derived in [2,4], and we have ( )…”

A possible spin-fluctuation mechanism in the emergence of superconductivity in a region of magnetic instability, using the example of PuCoGa5

“…tion temperatures of the SF amplitude ( ) for each subsystem. At , longitudinal SFs disappear [7,8], while the spin rigidity coefficient is always positive.…”

“…Short wavelength fluctuations of exchange fields (when the radius of spin correlations is smaller than the sizes of Cooper pairs) are necessary for the emergence of instability relative to singlet pairs due to the paramagnon mechanism. Our analysis of the renormalization of the electron spectrum, which leads to superconductivity, was based on the use of interpo lation fluctuation theory [8], which describes both large scale and short wavelength spin fluctuations (SFs). Under these conditions, we derive an equation associated with the superconductivity temperature from (3):…”

“…Let us calculate statistical sum Z = Sp(s(β)) by the saddle point method over variables ( = for ) (see [8]). In this pro cedure, we determine the most probable configuration of stochastic fields, which is characterized by the aver age value of the square of the exchange field at the site while the squares of the transverse and longitudinal components of the stochastic field are proportional (in the paramagnetic case) to the amplitudes of fluctuations of the corresponding com ponents of spin density and are determined from sad dle point conditions [8].…”