Spin-Phonon Coupling in A2BMnO6 (A = La, Pr, Nd, Sm, Gd; B = Co, Ni) Double-Perovskite Thin Films: Impact of the A-Site Cation Radius

Two series of B-site ordered, double-perovskite A2CoMnO6 and A2NiMnO6 (A = La, Pr, Nd, Sm, Gd) epitaxial films with thickness d ~ 100 nm were grown on SrTiO3(111) substrates via metalorganic aerosol deposition. Polarization temperature-dependent Raman spectroscopy carried out in order to determine the spin-phonon coupling constant, λ, impact A-site cation radius phonon properties. The reduction from La3+ down Gd3+ systematically shifts modes lower wavenumbers, decreases magnetization-induced softening Ag breathing mode, described by which changes λ 1.42 cm−1 (La2CoMnO6) 1.53 (La2NiMnO6) 0.58 (Gd2CoMnO6) 0.44 (Gd2NiMnO6). A similar effect A-cation was established for c-lattice parameter Curie temperature, TC, this films. Our observations directly demonstrate a strong lattice structure ferromagnetic superexchange interaction double perovskites. Moreover, exhibit very behavior due only moderate difference Co2+ Ni2+ size.