Local symmetry breaking in Eu1−xLaxB6

Abstract We report inelastic light (Raman) scattering study of Eu 1− x La x B 6 ( x = 0 , 0.05 , 0.1 , 0.2 , 0.3 ). As La is doped, the T 2g mode becomes broad and asymmetric, the E g mode splits into doublet, and the A 1g mode shifts to higher frequencies, while the undoped EuB 6 show sharp three phonon peaks, T 2g , E g , and A 1g modes. There are around six possible phonon peaks in the Raman spectra of La-doped EuB 6 . These additional peaks are explained by symmetry lowering of boron octahedra due to tilting/rotating.