Unveiling the Local Structure of Cu2+Ions from d-Orbital Splitting. Application to K2ZnF4:Cu2+and KZnF3:Cu2.
This work investigates why Jahn-Teller (JT) transition-metal ions like Cu2+(d9) or Mn3+(d4) with octahedral coordination exhibit low-symmetry distortions of the CuF64-(or MnF63-) octahedron, when Cu2+replaces Zn2+either in the cubic perovskite KZnF3or in the layer perovskite K2ZnF4. The aim is to establish correlations between the splitting Δeof the parent Oheg(x2- y2, 3z2- r2) d orbitals and the low-symmetry local distortion ρ, allowing us to unravel the local structure of Cu2+introduced as an impurity into such perovskites. However, the question of whether tetragonal a1g- b1gsplitting Δeof Cu2+is proportional to ρ or Δecontains additional contributions from the rest of the lattice (crystal anisotropy) is controversial. Here we show that Δedepends linearly on ρ. High-pressure experiments and compound series involving JT ions give support for the proposed scenario and provide correlations relating ρ and Δein Cu2+and Mn3+systems, from which the electron-vibration coupling for the E⊗e JT effect is obtained experimentally.
MALTA Consolider Team, Earth Science and Condensed Matter Physics Department (DCITIMAC), Facultad de Ciencias, University of Cantabria , 39005 Santander, Spain.
Fernando
http://orcid.org/0000-0002-7237-7443
F
Rodríguez