Spin-Peierls Transitions in Magnetic Fields —Thermodynamic Properties of a Soliton Lattice State—

Abstract

Spin-Peierls transitions under magnetic fields in a Heisenberg antiferromagnetic linear chain coupled to the spin-lattice distortion are discussed theoretically. Based on the mean-field Pytte Hamiltonian thermodynamic quantities such as magnetization, susceptibility and specific heat are derived, using the soliton lattice solution for the incommensurate state which takes into account infinite numbers of higher harmonics. The experimental data on TTF–MBDT (M=Cu and Au) and MEM (TCNQ)₂ are examined.