Effect of spin ordering on the magnetic contribution to the Kapitza conductance between two spin systems

Abstract

A theoretical discussion of the temperature and magnetic-field dependence of the contribution to the thermal boundary conductance (Kapitza conductance) from the interaction between liquid-${\mathrm{He}}^3$ nuclear spins and electron spins in a magnetic solid is presented for the case where $T$ lies below the ordering temperature $T_0$ of the solid. Our calculations apply to the temperature range $3\le T\le 100$ mK, where the ${\mathrm{He}}^3$ may be regarded as a normal Fermi fluid. We consider three cases: (i) a dilute alloy with magnetic impurities which experience random internal fields, (ii) an array of ferromagnetically aligned spins arranged on a crystal lattice, and (iii) a ferromagnetically aligned, but spatially disordered, array of spins. We also examine the presently available data on the magnetic contribution to $R_K$ in the light of the theoretical results.