An interpretation is given of the broadened EPR spectra of Gds+ ions, which are frequently observed in polycrystalline ceramics and glasses. A reasonable simulation of the spectra is obtained, when these are regarded as a superposition of a large number of normal EPR powder spectra, each of which can be described with the usual spin-Hamiltonian. These originate from the many different surroundings of the Gd3+ ions in these compounds due to the structural disorder. The result is, that only those transitions, which are independent of the zero field splitting parameters in the spin Hamiltonian, remain visible in the derivative spectrum. The interpretation is supported by the EPR powder spectrum of the Gd3+ doped compound CaHf,O,, which changes from broadened into clearly resolved, when the compound is ordered by an annealing process.Eine Interpretation wird fur die verbreiterten EPR-Spektren von Gd3 +-Ionen gegeben, die hLufig in polykristalliner Keramik und Glasern beobachtet werden. Eine ziemlich gute Simulation dieser Spektren wird erhalten, wenn diese Spektren als Summe einer groBen Anzahl normaler EPRSpektren betrachtet werden, welche mit dem ublichen Spin-Hamiltonoperator beschrieben werden konnen. Die normalen Spektren werden von den vielen verschiedenen Umgebungen der Gd3+-Ionen verursacht, als Folge der strukturellen Unordnung in diesen Verbindungen. Das Ergebriis ist, da13 nur solche Resonanzen wahrnehmbar sind im abgeleiteten Spektrum, die unabhangig von den Parametern der Nullfeldaufspaltung im Spin-Hamiltonoperator sind. Diese Interpretation wird durch das Verhalten des EPR-Spektrums eines Polykristalls der Gd3+-dotierten Verbindung CaHf,O, gesttitzt. Das erst verbreiterte Spektrum andert sioh in ein deutlich aufgespaltenes Spektrum, wenn die Verbindung in einem TemperungsprozeB geordnet wird.
Calculation methods for the evaluation of the parameters g, D and E for an S = 1 system, from paramagnetic resonance powder spectra are discussed and applied toa number of compounds having the general formula Ni(ligand),(anion),; in this formula the ligands are nitrogen donors such as nitriles, pyrazoles and imidazoles, with large anions like CIO;, BF;, SbCl,, InBri and GaCI;.A treatment similar to that of organic triplet molecules can be used for the interpretation, despite the fact that the observed bands are rather broad.In the present compounds the g-values were found to be isotropic within experimental error in the region 2.17-2.20; the D-values varied from 0.05-0.90 cm-' in the several compounds. The rhombic distortion (usually expressed as h = E/D) was found to be small for most compounds, although li -values of 0.10, 0.16 and 0.33 were also found.
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