Search results for "Mössbauer effect"
showing 10 items of 49 documents
Study of thermal spin crossover in [Fe(II)(isoxazole)(6)](BF4)(2) with Mossbauer spectroscopy
2007
Fe-57 Mossbauer spectroscopy of the mononuclear [Fe( II)( isoxazole)(6)]( BF4)(2) compound has been studied to reveal the thermal spin crossover of Fe( II) between low- spin ( S = 0) and high- spin ( S = 2) states. A temperature-dependent spin transition curve has been constructed with the least- square fitted data obtained from the Mossbauer spectra measured at various temperatures in the 240 - 60 K range during the cooling and heating cycle. The compound exhibits a temperature- dependent two- step spin transition phenomenon with T-SCO ( step 1) = 92 and TSCO ( step 2) = 191 K. The compound has three highspin Fe( II) sites at the highest temperature of study; among them, two have slightly …
Spin crossover in solid solution
1980
Abstract The temperature dependent high spin (HS) ⇌ low spin (LS) transition, otherwise called spin crossover, has been well established for many first-row transition metal complexes, particularly for complexes of iron(II) [1]. The phenomenon has been observed mostly in the crystalline state, but also in solution. The spin crossover characteristics have been found to depend on various chemical influences, such as ligand substitution, the nature of the non-coordinating anion and the crystallizing solvent. It has been shown by 57Fe Mossbauer spectroscopy that the spin crossover behaviour in the solid solutions of [FexZn1−x(2-pic)3] Cl2·EtOH (2-pic = 2-picolylamine) is also susceptible to meta…
Mössbauer study and non-linear excitations in the antiferromagnetic chain of Rb2Mn1−xFexF5*H2O (x≤0.50)
1989
Mossbauer effect measurements have been performed on the quasi 1-d antiferromagnetic solid solutions of Rb2Mn1−xFexF5*H2O (x=0.50) as a function of temperature. Particular attention was paid to the region very close to the Neel point. The experimental spectra show definite relaxation effects which are attributed to short-range order with temperature dependent relaxation times. The solitor, model of non-linear excitations was applied. Experimental data on Fe(III) confirm the predicted exponential temperature dependence of the thermal excitation of moving domain walls.
Observation of substitutional Fe in CEMS measurements on synthetic CVD diamond
2004
Conversion electron Mossbauer spectroscopy measurements have been made on a diamond sample synthesized by chemical vapour deposition. The sample was implanted with 70 keV 57Fe to a dose of 5 × 1014 cm−2 and Mossbauer measurements were made on the as-implanted sample and after annealing at temperatures of 600 K, 950 K and 1470 K. The spectra at the lower temperatures were characterized by broad doublets, but the annealing at 1470 K resulted in dramatic decrease in the intensity of the doublet components, and the appearance of a strong single line with an isomer shift of δ = −0.90(5) mm/s and areal intensity of 30%, and a weaker line (5%) with δ = +0.07(4). Arguments are presented to attribut…
Electric hyperfine interaction in199Hg fluorides
1985
With the current integration technique, the Mossbauer effect on the 158 keV, 5/2−→1/2− transition in199Hg was studied using the cubic HgF2 and the tetragonal Hg2F2 as absorbers; in the latter, a quadrupole splittingeQVzz=}- 9.0(2) mm/s was observed. Electron densities were calculated with the self-consistent-charge-extended-Hueckel-molecular-orbital method and δ〈r2〉=(3.26±0.11) fm2 derived. From the quadrupole splitting and the calculation, an effective antishielding factor almost twice that of the neutral Hg atom is derived.
Mössbauer effect study of the temperature and pressure dependence of the singlet-quintet intersystem crossing dynamics in an iron(II) spin crossover …
1988
The lineshapes of Mossbauer spectra of the iron(II) spin crossover complex [Fe(6-mepy)3 tren] (PF6)2 are affected by the dynamics of the HS⇌LS equilibrium. The lineshapes are reproduced with a stochastic two-state-relaxation-model yielding rate constants similar to those determined for related complexes in solution. Application of an external pressure of 150 MPa increases the relaxation rate.
Rayleigh scattering of Mössbauer radiation on a myoglobin single crystal
1992
The RSMR technique was used to determine the fraction of radiation which is scattered elastically and inelastically, respectively, into Bragg reflections of a metmyoglobin single crystal. From this measurement 〈x2 1c〉=0.027±0.008 A2 has been determined which is due to long range correlated motions in analogy to acoustic and optic modes in solids.
On the metal distribution in the system GeTe−Sb2Te3
1988
The structures of GeSb2Te4, Ge2Sb2Te5 and GeSb4Te7 are not determined completely by means of classical X-ray or electron diffraction studies. We have measured the Mossbauer parameters of121Sb in these compounds as well as in their binary constituent Sb2Te3 as an attempt to improve our knowledge on the question.
Polarized neutron diffraction and Mössbauer spectral study of short-range magnetic correlations in the ferrimagnetic layered compounds(PPh4)[FeIIFeII…
2002
Short-range antiferromagnetic correlations have been studied in the layered compounds (PPh 4 ) [Fe I I Fe I I I (ox) 3 ] and (NBu 4 ) [Fe I I Fe I I I (ox) 3 ] by neutron polarization analysis and Mossbauer spectroscopy. Polarized neutron diffraction profiles obtained between 2 and 50 K on (d 2 0 -PPh 4 ) [Fe I I Fe I I I (ox) 3 ] show no magnetic Bragg scattering; the lack of such scattering indicates the absence of long-range magnetic order. However, a broad asymmetric feature observed at a Q of ca. 0.8 A - 1 is attributed to two-dimensional short-range magnetic correlations, which are described by a Warren function. The correlation length is ca. 50 A between 2 and 30 K and then decreases…
Effect of cation disorder on the magnetic properties ofSr2Fe1−xGaxReO6(0<x<0.7)double perovskites
2007
The effect of diamagnetic dilution of the Fe sublattice on the structural and magnetic properties of the double perovskite Sr{sub 2}Fe{sub 1-x}Ga{sub x}ReO{sub 6} (0 =}0.4 is detected by x-ray structural analysis accompanied by the observation of a magnetically ordered and a paramagnetic phase in the corresponding Moessbauer spectra. Below 20% Ga content, Ga statistically dilutes the -Fe-O-Re-O-Fe- double-exchange pathways. Phase separation begins at 20% Ga substitution; between 20% and 40% ofmore » Ga content, the paramagnetic Ga-based phase does not contain any Fe. The Fe-containing, paramagnetic cubic phases which can be detected by Moessbauer spectroscopy first appear for x=0.4.« less