Electronic structure of GdTX compounds

B. Tyszka^a, J. Szade^a, W. Burian^a,

M. Sikora^b, D. Zając^b,Cz. Kapusta^b,

M. Matteucci^c, F. Bondino^c, M. Zacchigna^c, M. Zangrando^c

^aUniversity of Silesia, A. Chelkowski Institute of Physics, Uniwersytecka 4, 40-007 Katowice, Poland

^bAGH University of Science and Technology, Mickiewicz Avenue 30, 30-059 Krakow, Poland

^cINFM-TASC, Beamline BACH, AREA Science Park, 34012 Basovizza, Trieste, Italy

GdTX compounds, where T- is a transition metal and X- Ge or Si, have attracted much attention due to their interesting electronic and magnetic properties.

GdTiGe crystallises in the tetragonal CeScSi structure type (I4/mmm) and exhibits ferromagnetic type of ordering with a high T_C=374 K. The compounds GdTi_1-xMn_xGe (x=0.1-0.6) have the same type of structure and order also ferromagnetically with Curie temperatures reaching 430 K. Especially interesting question is the influence of Mn atoms on the magnetism of the compounds. GdMnGe has the orthorhombic TiNiSi type of structure (Pnma) and shows an antiferromagnetic character of ordering with two transitions at 102 K and 337 K [1].

With this work we studied the electronic structure of the group of compounds in order to understand the peculiar properties. X-ray Photoelectron Spectroscopy (XPS) and Ultraviolet Photoelectron Spectroscopy (UPS) have been used to study the valence band and core levels. The valence band photoemission spectra have been compared with the results of the TB LMTO calculations [2,3]. The exchange splitting of the core levels has been analysed in relation to the magnetic properties.

Additionally we have investigated the magnetic electronic structure of these compounds using X-ray Absorption Spectroscopy (XAS) and X-ray Magnetic Circular Dichroism (XMCD) measurements in the Mn, Ti and Gd core absorption regions. The element specific excitations have been studied using Resonant Inelastic X-ray Scattering (RIXS). We have obtained also the resonant photoemission spectra for GdTiGe. The resonant emission spectra were acquired with the ComIXS fluorescence spectrometer at the excitation thresholds of all elements. The RIXS spectra show a resolved structure with elastic peak, fluorescent lines and weak resonant features. The experiment was performed at the Beamline for Advanced Dichroism (BACH) of ELETTRA (Trieste-Italy). The spectra are discussed in relation to XAS and XPS data and the electronic structure calculations.

[1] B. Tyszka, J. Szade, J. Alloys Comp. 354 (2003) 64

[2] G. Skorek, J. Deniszczyk, J. Szade, B. Tyszka, J. Phys.: Condensed Matter 13 (2001) 6397

[3] B. Tyszka, J. Szade, J. Deniszczyk, J Magn. Magn. Mater., in press