Effects of spin-phonon interaction on transport, magnetic properties and the oxygen isotope effect in R1-xAxMnO3

We consider the spin-phonon (s-p) coupling as an important correction to the double exchange and the dynamic Jahn-Teller effect in colossal magnetoresistance systems R(1-x)A(x)MnO(3). The effect of s-p on transport, magnetic properties and the oxygen isotope effect has been studied by utilizing the perturbation theory and mean field theory. It is indicated that (i) a formula for the shift of the ferromagnetic (FM) transition temperature T-c is given, from which it could be seen that the s-p coupling could yield an excitation gap for long-wavelength acoustic spin waves and an applied field could improve T-c, (ii) the relation T-c similar to m(-1/2) (m is the mass of the anion) is obtained, which suggests that the oxygen isotope effect is dominated by both the s-p and e-p interaction, (iii) it could cause the hardening of phonon frequency in the FM state, (iv) s-p could lead to the increase of the resistivity which is proportional to T-3 at low temperature and proportional to T at high temperature in the ferromagnetic metallic region of R(1-x)A(x)MnO(3). (C) 2011 Elsevier B.V. All rights reserved.