Impact ofCo∕Mncation ordering on phonon anomalies inLa2CoMn

Abstract

Manifestation of Co/ Mn ordering on the spin-lattice dynamics of La 2 CoMnO 6 ͑LCMO͒ double perovskites is studied by Raman spectroscopy. We investigate the temperature dependence of the magnetic and the optical properties for ͑i͒ microcrystals containing both the ordered and disordered phases and ͑ii͒ Co/ Mn ordered epitaxial films. Our results show distinct onsets of phonon mode softening in the vicinity of the magnetic phase transitions, revealing a strong spin-lattice coupling in LCMO. Moreover, Co/ Mn ordering in the thin films leads to the appearance of additional excitations that had not been observed previously. We interpret these features as a result of Brillouin zone folding due to the doubling of the unit cell in the ordered phase.

Ferromagnetism and magnetodielectric effect in insulating LaBiMn4∕3Co2∕3O6 thin films

“…16 To further investigate the presence of weak spin -lattice coupling, the local structure of the thin films was investigated by polarized Raman spectroscopy. 17,18 Temperature dependence Raman spectra were measured on film samples grown on both STO and LAO surfaces in the x'x', xx, xy, and x'y' polarization configurations.…”

Stabilization and functional properties of La3NiAlMnO9 and La3CoAlMnO9 magnetoelectric triple perovskites

“…For LNAMO, it is about 3.99 Å. Surprisingly, these artificial oxides show a significant enhancement in their pseudo-cubic lattice parameter compared to their respective LCMO (~ 3.89 Å) and LNMO (~ 3.87 Å) bulk and thin films [6][7][8][9][10][11][12][13][14] . We interpret this counter-intuitive behaviour as an indication that the presence of Al in the crystal structure provokes an expansion of the out-of-plane lattice parameter to minimize the elastic and columbic energy of these polar systems.…”

“…Stabilizing the complex self-ordered triple-perovskite structure requires very specific growth conditions as was shown for double-perovskite LCMO [9][10][11][12] To study the presence and magnitude of the spin-phonon coupling, we investigated the LCAMO thin films by polarized Raman spectroscopy, which has been a proven technique to investigate local lattice distortions, cation ordering, spin-lattice coupling and phase transitions in ferromagnetic insulators as La 2 CoMnO 6 and La 2 NiMnO 6 epitaxial films [8][9] . We measured the temperature dependence of Raman phonon frequencies from 10 to 300 K using a Labram 800 microscope spectrometer equipped with a He-Ne laser (λ = 632.8 nm).…”

“…In our recent studies of self-ordered La 2 CoMnO 6 (LCMO) thin films grown by pulsed-laser deposition, we demonstrated that the ordered Co/Mn cations can be obtained only in a limited window of growth parameters 11 . It has been clearly established that the magnetic behaviour of these compounds is a very sensitive probe of the presence of cation ordering [5][6][7][8][9][10][11][12][13][14] . Furthermore, the MnO 6 and CoO 6 layers with Mn 4+ and Co 2+ ions alternating along the (111) crystal axis generate a strong polar character as confirmed by an enhanced dielectric constant 14 and a large magnetodielectric coupling in the vicinity of the magnetic phase transition 7,[14][15] .…”

“…and A = La) represent an alternative avenue to search for such innovative materials [4][5][6][7][8][9][10][11][12][13][14][15] .…”