INTERFACE FORMATION AND A STRUCTURAL PHASE-TRANSITION FOR THE SPHERICAL MODEL OF FERROMAGNETISM

A detailed analysis is reported examining the local magnetic susceptibility chi(r), in relation to the correlation function GIR) and correlation length xi, of a spherical model ferromagnet confined to geometry Omega = L(d-d') x infinity(d') (d' less than or equal to 2, d > 2) under a continuous set of twisted boundary conditions. The ''twist'' parameter ($) under bar tau in this problem may be interpreted as a measure of the geometry-dependent doping level of interfacial impurities (or antiferromagnetic seams) in the extended system at various temperatures. For tau(j) --> 0, For All j is an element of d-d', no seams are present except at infinity, whereas if tau(j) = 1/2, impurity saturation occurs. For 0 < tau(j) < 1/2 the physical domain Omega(phys) = D-d-d' x infinity(d') (D > L), defining the region between seams containing the origin, depends on temperature above a certain threshold (T > T-0). Below that temperature (T < T-0), seams are frozen at the same position (D approximate to L/2 tau, d-d' = 1), revealing a smoothly varying large-scale structural phase transition.