Sign Of Electric Field Gradient Research Articles

57Fe Mössbauer study of new multiferroic AgFeO2

The present work reports results of the 57Fe Mossbauer measurements on AgFeO2 powder sample recorded at various temperatures including the points of both magnetic phase transitions. The 57Fe Mossbauer spectra of AgFeO2 measured in the paramagnetic range (T > T N1) consist of one quadrupole doublet with rather high quadrupole splitting of Δ300K = 0.66 ± 0.01 mm/s for Fe3+ ions. In order to predict the sign of electric field gradient (EFG) at 57Fe nuclei, we calculated the lattice contribution to the electric field gradient (EFG) at 57Fe nuclei, which emphasized the importance of the dipolar contributions, with resultant oxygen polarizabilities in the range of α O = 0.83 A3, in agreement with the results obtained previously for other delafossite-like oxides. In the temperature range of T N2 < T < T N1, Mossbauer spectra gave clear evidence for the existence of a distribution of the hyperfine magnetic fields H hf at 57Fe nuclei. We present the results of a model fitting of the spectra based on an assumption of the cycloid magnetic structure of AgFeO2 at T < T N2. The obtained data were analysed in comparison with published data on Mossbauer studies of oxide multiferroics.

Hyperfine Interactions and Dynamic Characteristics of 119Sn Dopant Atoms in Ca2Fe2O5

119Sn Mossbauer spectra of tin impurity ions located in the bulk of Ca2Fe2O5 particles have been investigated over the 77–1070 K temperature range. This study has allowed us to determine the sign of electric field gradient (EFG) as well as the angle between directions of the main EFG axis and magnetic field induced at 119Sn nuclei. The values obtained appear to be in a good accordance with distorted octahedral coordination of 119Sn4+ ions. Analysis of the asymmetry of the 119Sn quadrupole doublet at T>TN showed that the mean-square amplitudes of Sn4+ thermal vibrations along the EFG direction are greater than those in the perpendicular direction. The temperature behavior of the 119Sn spectra is described in terms of the Debye model.

Mössbauer and Infrared Spectroscopic Studies of Some Alkyl- and Arylamine Coordinated Pentacyanoferrate(II) Complexes

Abstract Mössbauer spectra of alkyl- and arylamine coordinated pentacyanoferrate(II) complexes, Na3[Fe(CN)5L]·xH2O where L=(CH3)3N, (CH3)2CHNH2, (CH3)2CHCH2NH2, (CH3)3C–NH2, C6H5NH2, C6H5NHCH3, C6H5N(CH3)2, C6H5NHC2H5, o-ClC6H4NH2, and p-ClC6H4NH2 have been studied. All compounds exhibit a well-resolved quadrupole doublet. An unusually high quadrupole splitting is observed for isobutylamine coordinated complex (ΔEQ=1.75 mm s−1). Other complexes show ΔEQ=0.67–0.86 mm s−1. A correlation of δ vs. ΔEQ suggests a positive sign of electric field gradient for isobutylamine coordinated complex and negative for all other complexes. Partial isomer shift (p.i.s.) and δ have been correlated with partial quadrupole splitting (p.q.s.). Also characteristic CN and Fe–N stretching frequencies have been correlated with δ to derive information on σ-donor and π-acceptor properties of the ligands.

Quadrupole interaction at the Eu site in the EuBa 2Cu 3O 7− x superconductor

151Eu Mössbauer measurements have been performed on magnetically aligned samples of EuBa 2Cu 3O 7- x at room temperature to prove that line broadening and asymmetry are caused by quadrupole interaction at the Eu 3+ site. The sign of electric field gradient was found to be negative ( eQV zz = −4.46 mm/ s, S = 0.66 mm/ s, η = 0.7). the main axis of the EFG tensor was found to be parallel to the c axis of the superconductor crystal.

Electric field gradient at 57Fe in scandium and systematics of the electric field gradient at impurities in transition-metal hosts.

The electric field gradient (EFG) at /sup 57/Fe probe atoms in hcp transition-metal scandium is measured using Moessbauer spectroscopy, with /sup 57/Fe as a dilute impurity in pure scandium metal. The quadrupole splitting obtained is 0.26(2) mm/s and the corresponding EFG is 1.3(1) x 10/sup 17/ V/cm/sup 2/ at the probe site in scandium. The ratio eq/sup el//eq/sup ion/ is in fairly good agreement with the universal correlation proposed by Raghavan et al. The results are compared with the theoretical value of the EFG calculated using the conduction-electron charge-shift model. Also, a systematic scheme, which can be used to determine eq/sup el/ and the sign of EFG in transition-metal hosts, is proposed.

Correlation of isomer shift and quadrupole splitting and the sign of EFG

Mossbauer isomer shift /δ/ and quadrupole splitting /ΔEQ/ values in a series of isostructural compounds correlate well to give linear relationship provided the sign of electric field gradient /EFG/ is assigned to the ΔEQ. The correlation has been used in predicting the sign of EFG for some monosubstituted pentacyanoferrate/II/ complexes. Usefulness of such correlations and its limitations are presented.

Sign of electric field gradient at 57Fe nuclei in garnets

Mössbauer spectra of 57 Fe in seven polycrystalline garnet samples were measured at room temperature in an applied magnetic field. The signs of electric field gradients at octahedral and tetrahedral lattice sites have been determined.

On the quadrupole splitting ‐isomer shift linear correlationship and the sign of electric field gradient

On the quadrupole splitting ‐isomer shift linear correlationship and the sign of electric field gradient