Role of electron correlation and long range magnetic order in the electronic structure of Ca(Sr)RuO3

The room temperature photoemission spectra collected at different surface sensitivities reveal qualitatively different surface and bulk electronic structures in CaRuO3 and SrRuO3. The extracted bulk spectra are dominated by the coherent feature intensity with a weak correlation induced feature at higher binding energies. The First principle calculations provide a wonderful representation of the bulk spectra for the effective electron correlation strength, U/W similar to 0.2 as expected for highly extended 4d systems. This resolves a long-standing issue that arose due to the prediction of large U/W similar to 3d systems. Photoemission spectra across the magnetic phase transition reveal unusual evolution exhibiting a large reduction in the coherent feature intensity in the bulk spectrum of SrRuO3, while the bulk spectrum in CaRuO3 remains almost the same down to the lowest temperature studied. (C) 2007 Elsevier B.V. All rights reserved.