Theory of resonant spectroscopies in nickel, cerium compounds and other systems

Abstract

Abstract In this paper, we discuss theoretically information about electronic structures in strongly correlated systems obtained from resonant X-ray spectroscopies. From a many-body point of view on the basis of an impurity Anderson model or a cluster model including the intra-atomic multipole interaction between electrons, we calculate spectra by exactly diagonalizing our Hamiltonian. First, for ferromagnetic Ni, through an analysis of magnetic circular dichroism in 3 d resonant photoemission spectroscopy (RPES) and resonant inverse photoemission spectroscopy (RIPES), it is shown that, in addition to 3 d 9 and 3 d 10 , the 3 d 8 configuration with weight of about 20% is contained as electron configuration of a Ni atom in Ni metal. The 3 d 8 configuration is furthermore shown to be mainly composed of 3 F and its relation to the origin of ferromagnetism is discussed. Second, for mixed valent Ce compounds, including CeNi 2 , it is shown, through an analysis of RIPES, tht the 4 f -conduction band hybridization must be reduced by the presence of a core hole. Third, for some 3 d transition metal (TM) oxides, 3 d RPES at TM ion 2 p threshold is shown to be a powerful method for estimating the magnitude of 3 d –3 d interaction strength and the charge transfer energy.