Broken translational and rotational symmetries in LiMn_1.5Ni_0.5O₄ spinel

Abstract

In condensed matter physics broken symmetries and emergence of quasi-particles are intimately linked to each other. Whenever a symmetry is broken, it leaves its fingerprints, and that may be observed indirectly via its influence on the other quasi-particles. Here, we report the strong signature of broken rotational symmetry induced due to long range-ordering of spins in Mnsublattice of LiMn1.5Ni0.5O4 below Tc ~ 113 K reflected with the marked changes in the lattice vibrations using Raman scattering. In particular, the majority of the observed first-order phonon modes show a sharp shift in frequency in the vicinity of long range magnetic-ordering temperature.Phonons exist in a crystalline system because of broken translational symmetry, therefore any renormalization in the phonon-spectrum could be a good gauge for broken translational symmetry.Anomalous evolution of the few modes associated with stretching of Mn/NiO6 octahedra in the intermediate temperature range (~ 60-260 K) marked the broken translational symmetry attributed to the charge ordering. Interestingly same modes also show strong coupling with magnetic degrees of freedom, suggesting that charge-ordering and magnetic transition may be linked to each other.

Anomalous phonon renormalization in single crystal of silicon

“…The change in the phonon mode frequency considering the above effect may be given as ( ) ( ) ( )  is mode frequency at T = 0 K and c is a constant. To extract the thermal expansion coefficient above 60 K, we have fitted the mode frequency using the following equation [10][11][12]:…”

Unraveling the effects of inter-site Hubbard interactions in spinel Li-ion cathode materials

“…Unfortunately, for LiMn 1.5 Ni 0.5 O 4 and Mn 1.5 Ni 0.5 O 4 there are no experimental data for the band gaps, to the best of our knowledge; however, the work of Ref. [90] states that LiMn tively, are the most reliable ones and should be used for comparisons in the future computational and experimental works.…”

Coupling of lattice, spin, and intraconfigurational excitations of Eu3+ in Eu2ZnIrO6

“…On further lowering the temperature, mode frequency exhibits a sharp decrease down to the lowest recorded temperature, while the corresponding damping constant shows normal behavior phase, of magnetic materials is generally attributed to the entanglement of lattice with underlying spin degrees of freedom via strong spin-phonon coupling [26,28,[31][32]36].…”

“…Raman spectroscopy is a sensitive and effective technique for probing the underlying lattice, magnetic and electronic degrees of freedom, and is extensively used to unravel the coupling between a range of quasiparticles in solids such as magnons, orbitons, excitons and phonons [23,[26][27][28][29][30][31][32]. It is basically a photon-in-photon-out process in which an incident photon of energy i  is inelastically scattered by the system under consideration into a photon of energy s  .…”