Spin-phonon interaction in the compressible Ising magnet. III

摘要: For pt. II see abstr. A62238 of 1971. The effective spin hamiltonian containing a four-spin term which arises from allowing harmonic phonons to be included in the Ising model was solved molecular field approximation (MFA) an earlier paper by two authors. A brief review is given MFA results with methods deriving result both simpler than that first publication. need for employing ensemble average nearest neighbour correlation function pointed out and it shown this elastic strain lattice proportional function. problem then studied at equivalent quasichemical or Bethe-Peierls pure long range order are employed explicitly. As MFA, nature phase transition changes second as strength spin-phonon coupling increased. High temperature contributions thermal expansion calculated.