Origin of Superexchange Interactions in 3d Magnetic Solids (I)

Role of thermal vibrations in magnetic phase transitions

“…This is a lattice dynamic effect and not due to Jahn-Teller interactions. An expression for the exchange intergral at finite temperatures has been derived as [34][35][36] 14 ⁄ 1 (12) where J 0 is the Heisenberg exchange at 0 K, i.e. J ij (0) in Eq.1, and K J is the spin-lattice coupling constant.…”

“…In the case of insulators, a phonon mediated superexchange mechanism has been proposed [34][35][36]. This is a lattice dynamic effect and not due to Jahn-Teller interactions.…”

“…This is a lattice dynamic effect and not due to Jahn-Teller interactions. An expression for the exchange intergral at finite temperatures has been derived as [34][35][36] 14…”

“…Thus, the observed isotope effect [31,32] and the theory of phonon mediated superexchange [34][35][36] suggest that even when vibration amplitudes are relatively small at low temperatures, the exchange integral must be represented as temperature dependent, J ij (T). This is completely consistent with our conclusion based on the analysis of neutron diffraction data that as a general principle, the exchange interaction must be represented to be temperature dependent, J ij (T), and Eq.5 must replace Eq.1 as the prototype model for magnetic phase transitions.…”