Interplay of lattice, electronic, and spin degrees of freedom in detwinned BaFe2As2 : A Raman scattering study

Abstract

We report results of Raman scattering experiments on twin-free BaFe2As2 with the main focus placed on understanding the influence of electronic and spin degrees of freedom on the lattice dynamics. In particular, we scrutinize the Eg modes and the As A1g mode. Each of the two Eg phonons in the tetragonal phase is observed to split into a B2g and a B3g mode upon entering the orthorhombic stripe-magnetic phase. The splitting amounts to approximately 10 cm −1 and less than 5 cm −1 for the low-and the high-energy Eg mode, respectively. The detailed study of the fully symmetric As mode using parallel incident and outgoing photon polarizations along either the antiferromagnetic or the ferromagnetic Fe-Fe direction reveals an anisotropic variation of the spectral weight with the energy of the exciting laser indicating a polarization-dependent resonance effect. Along with the experiments we present results from density functional theory calculations of the phonon eigenvectors, the dielectric function, and the Raman tensor elements. The comparison of theory and experiment indicates that (i) orbital-selective electronic correlations are crucial to understand the lattice dynamics and (ii) all phonon anomalies originate predominantly from the magnetic ordering and the corresponding reconstruction of the electronic bands at all energies.

Symmetries of modes in Ni3V2O8: Polarized Raman spectroscopy and ab initio phonon calculations

“…Many magnetic systems have been explored using Raman spectroscopy across magnetic transitions with the interest of phonon‐spin anomalies. Although CaFe 2 O 4 has shown no phonon anomaly near transition temperature, the anomalies close to the transition temperature are discussed in PrMnO 3 , NdMnO 3 , TbMnO 3 , and DyMnO 3 using polarized Raman spectroscopy and the phonon anomalies observed in BaFe 2 As 2 , which are attributed to spin–lattice electronic coupling. Polarized Raman measurements enabled observation of transient lattice disorder in very narrow temperature intervals at the onset of the multiferroic ordering in Eu (1‐x) Ho x MnO 3 and Higgs modes in the 2‐D antiferromagnet Ca 2 RuO 4 providing strong evidence for excitonic magnetism in it .…”

In-plane uniaxial pressure-induced out-of-plane antiferromagnetic moment and critical fluctuations in BaFe2As2

“…These results indicate that in addition to detwinning BaFe 2 As 2 , uniaxial pressure applied on the sample actually modifies the magnetic structure of the system. Therefore, infrared 45 , angle resolved photoemission 16 , and Raman spectroscopy 46 , 47 experiments on mechanically detwinned BaFe 2 As 2 near the magnetic and nematic phases should be reexamined to take into account the effect of strain-induced change to the spin anisotropy on the in-plane electronic and magnetic properties.…”

Temperature‐Dependent Raman Study of Nanostructured and Multifunctional Materials

“…The discovery of superconductivity in iron‐based materials has attracted a great attention of the solid state community. During the last decade many new classes of iron‐based materials with reach phase diagrams have been reported, featuring a variety of the (competing) phases, and their phonon properties have been extensively studied by using temperature‐dependent Raman spectroscopy . In order to demonstrate the ability of inelastic light scattering to probe a number of structural and/or magnetic properties of iron‐based materials, an overview of some published results is presented .…”