Abstract:
Summation formulas are derived for quasi-Taylor series that arise in the diagram
technique for spin operators and correspond to $m$-point correlations of the spins.
In the approximation of self-consistent pair correlations, we obtain an equation of
state of an Ising ferromagnet $(d=3)$ valid in a wide range of temperatures and
magnetic fields except for a narrow neighborhood of the critical point. In the same
approximation, we calculate the shape of the magnetic resonance line of the Ising
ferromagnet; it is Gaussian. In the limit $T\to\infty$, complete summation of the quasi-
Taylor series yields an exact expression for the line shape.
Fulltext:
PDF file (977 kB)
