The Simulation and Interpretation of the EPR Powder Spectra of Gd³⁺‐Doped LaAlO₃

Abstract

The EPR powder spectra of Gd3+ doped LaA10, are simulated for a number of temperatures between 4 and 800 K by means of the usual spin-Hamiltonian. Values are found for the zero field splitting parameters B(n, 0) only, which agree with single crystal measurements. For an accurate simulation of the axial powder spectra a variable linewidth has to be introduced, because an inhomogeneous broadening of the resonances in the zy plane is observed. This broadening is successfully described by a variable B(2, 2) parameter. This indicates that the Gd3+ ion does not fit within the LaA10, lattice, because GdAlO, is not isostructural with LaAlO,. Crystal field calculations support this assumption.Die EPR-Pulver-Spektren, der mit Gd3+ dotierten Verbindung LaAlO,, werden fur einige Temperaturen zwischen 4 und 800 K mit dem ublichen Spin-Hamiltonoperator simuliert. Nur fur die Nullfeldaufspaltung der Parameter B(n, 0) werden Werte gefunden, die mit Messungen an Einkristallen ubereinstimmen. Um eine gute Simulation der axialen Spektren des Polykristalls zu erhalten, ist eine variable Linienbreite notig, weil eine inhomogene Verbreiterung in der (2, y ) -Ebene beobachtet wird. Diese Verbreiterung wird erfolgreich durch verschiedene B(2,2) Parameter beschrieben. Daraus IaBt sich schlieoen, dao das Gda+-Ion sich nicht in das LaAl0,-Gitter einfugt, da die Gitterstrukturen von GdAlO, und LaA10, nicht ubereinstimmen. Berechnungen des Kristallfeldes unterstutzen diese Behauptung.

Importance of Fourth-Order Zero-Field Splitting Terms in Random-Orientation EPR Spectra of Eu(II)-Doped Strontium Aluminate

“…They confirmed the validity of the analysis by comparing with single-crystal EPR studies. Koopmans et al also demonstrated a parametrization procedure by the combined use of Abraham's approach and computer simulation based on numerical diagonalization of the spin Hamiltonian . On the other hand, we reported another approach using the hybrid-eigenfield method instead of the numerical diagonalization …”

“…Koopmans et al also demonstrated a parametrization procedure by the combined use of Abraham's approach and computer simulation based on numerical diagonalization of the spin Hamiltonian. 20 On the other hand, we reported another approach using the hybrideigenfield method instead of the numerical diagonalization. 21 In this work, the approach was extended by considering all fourth-order terms, and it can be addressed for other S ) 7/2 systems.…”