HEAT-CAPACITY OF SOLID-SOLUTIONS OF HE-3 IN HE-4

The authors have theoretically calculated the excess low temperature h eat capacity of solid solutions of helium isotopes with concentrations of a few per cents He-3 In He-4. It Is assumed that the impurity cont ribution to thermodynamics of the solution is due to phase stratificat ion of the solid solution and formation of quasi-one-dimensional struc tures of He-3 atoms during their deposition on lines of lattice disloc ations or construction of fractal structures. Excess heat capacity rep resents a peak in the temperature range 50-200 mK whose position at th e temperature axis depends practically only on the potential well dept h epsilon(0) similar or equal to -1 K which is due to a dislocation Fo r an impurity atom, the height depending primarily on the magnitude xi similar or equal to 10(-6)-10(-3), i.e. the fraction of the lattice p oints that can be occupied by the one-dimensional phase. The effect of the energy of interaction of impurities in the bulk crystal, V simila r or equal to 0.1 K, on the shape and position of the impurity heat ca pacity has been found insignificant. The theoretical result of the aut hors are in good agreement with experimental data for the solution wit h x(3) - 0.9% with single-valued choice of the adjustable parameters x i = 0.0058, V = = 0.3 K and epsilon(0) = -0.92 K.