Magnetic dynamic susceptibility of magnetic dipole glasses

The dissipative part of the linear magnetic dynamic susceptibility of a system of impurity magnetic dipoles in a crystal, which interact between themselves (predominantly by means of magnetic dipole-dipole interaction) and with lattice vibrations has been calculated. It is shown that the linear response of this system consists of resonance and relaxation parts. The anomalous temperature dependence of the dissipative part of the magnetic susceptibility caused by the transition of the system with sufficiently high concentrations of magnetic dipoles from the paramagnetic phase into a magnetic-dipole-glass phase has been determined.     

Geometry and nature of the interfacial layer in polyimide coatings

A new approach to the quantitative evaluation of the thickness h_i and the volume fraction V_i of the interfacial layer in polyimide coatings has been developed using the model of a one-sided polymer coating as a three-phase system (a substrate, an interfacial layer and a polymer matrix) and the method of differential scanning calorimetry. The new approach is characterized by the fact that a “pure” polymer matrix is modeled with the help of free films obtained on mercury. The formulas for the calculation of the thickness and volume fraction of the interfacial layer have been proposed. The value h_i has been determined in polymer coatings of different thicknesses on aluminium foil. This parameter has been shown to be independent of the film thickness if the latter is not larger than the length of the interfacial layer. An assumption has been made about the “mechanical” origin of thick (> 1–5 μm) interfacial layers, and their relaxation character has been revealed.