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

Crystals

Philipp Ksoll¹  Christoph Meyer¹  Vasily Moshnyaga¹  Vladimir Roddatis² 

[1] Erstes Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany;Institut für Materialphysik, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany;

关键词: double perovskites;    thin films;    Raman spectroscopy;    spin-phonon coupling;   

DOI  :  10.3390/cryst11070747

来源: DOAJ

【 摘 要 】

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

【 授权许可】

Unknown