E. Baggio-Saitovitch

57Fe and119Sn Mössbauer studies on La1.25Nd0.6Sr0.15CuO4

Abstract57Fe- and119Sn Mössbauer effect studies on 0.5 at %57Fe (or119Sn) dopednon-superconducting La1.25Nd0.6Sr0.15CuO4 in the temperature region 300 K ≧T≧4.2 K reveal an onset of local magnetic ordering occurring atTm≅32 K for both57Fe—as well as119Sn-doped samples. The local magnetic ordering shows up in the presence of a very large transferred hyperfine field ofBthf≅11.0(5)T at the119Sn nuclei. Since such a large field is neither present in antiferromagnetic La2CuO4, nor in superconducting La1.85Sr0.15CuO4 or overdoped La2−xSrxCuO4 (x=0.4), the occurrence of such local spin correlations seems to be a signature of the non-superconducting low temperature tetragonal phase of La1.25Nd0.6Sr0.15CuO4.

Dynamical properties of semiconducting Fe: YBaCuO

The vibrational behavior of iron in oxygen deficient YBaCuO has been studied by Mössbauer spectroscopy up to 770 K. Iron coordinated by four oxygen atoms reveals a significantly softer and anharmonic temperature dependence (temperature dependent θD) than iron with higher coordination (θD=600 K). Above about 650K oxygen diffusion leads to relaxation effects for two of the observed iron species.

Oxygen re-arrangement and desorption in 57Fe:Y-Ba-Cu-O

Abstract We report on in situ high temperature 57Fe Mossbauer measurements on several Fe:YBaCuO samples with different Fe concentrations under controlled oxygen partial pressures. The results are discussed in terms of the temperature dependent binding of oxygen in Fe-rich clusters which differs from that in their more Cu-rich surrounding.

Magnetic and Sn‐Mössbauer Characterization of Ruthenocuprate

Recent reports on the coexistence of superconductivity and weak‐ferromagnetism in ruthenocuprates have stimulated interest in these materials. The RuSr2RECu2O8 (Ru‐1212) (RE = Gd,Eu) compounds exhibit this unusual behavior and belong to the family of high‐temperature superconductors. Polycrystalline samples of (Ru1−xSnx)Sr2GdCu2O8 (x = 0.05, 0.1, 0.2, 0.3) have been prepared according to the standard solid state reaction methods. The 119Sn‐Mossbauer spectra for the (Ru1−xSnx)Sr2GdCu2O8 system were measured for the first time at room temperature and at 4.2°K. Spectral analysis, complemented with x‐ray diffraction, magnetic susceptibility, and isothermal magnetization measurements, reveals that Sn substitutes Ru at the RuO2 layers, giving the opportunity to change the carrier concentration in the hole‐underdoped parent compound. An in‐plane hyperfine transferred field of 4 T at 4.2°K was sensed at the (Ru,Sn)O2 layers. Because of its local character, Mossbauer spectroscopy is a unique technique for these on...

Hyperfine interactions in the intermetallic system Ce(Fe1−xAlx)2 Al-rich side

Abstract Investigations of the hyperfine interactions of the Ce(Fe 1− x Al x ) 2 system in the Al-rich side for 0.60 ≤ x ≤ 1.0 have been performed using Mossbauer spectroscopy at room temperature (RT) and 4.2 K, under applied magnetic fields B a ≤ 4.5T. The spectra can be analyzed in terms of two components, D1 and D2; the former one is associated with Fe in Ce(Fe 1− x Al x ) 2 and D2 to the spurious phase Ce 2 (Fe 17− x Al 3 ) that appears in small amounts, but is strongly magnetic.

Magnetic properties of Ce(Fe1−xAlx)2 intermetallic compound observed by Mössbauer spectroscopy at the Al-rich side

Abstract Mossbauer effect measurements at room temperature (RT) show paramagnetic spectra that can be conveniently analysed with two doublets, D1 and D2. At 4.2 K the spectra display a broad hyperfine distribution superimposed to a quadrupole doublet. The concentration dependence of the hyperfine parameters associated with D1 is reminiscent of the behavior at the Fe-rich side of the system while the origin of the other component is still under investigation.

57Fe and 119Sn Mössbauer studies on La1.25Nd0.6Sr0.15CuO4: Evidence for local magnetic ordering below ≂32 K (abstract)

57Fe and 119Sn Mossbauer effect studies on 0.5 at. % 57Fe or 119Sn doped nonsuperconducting La1.25Nd0.6Sr0.15CuO4 in the temperature region 300 K≥T≥4.2 K reveal an onset of local magnetic ordering occurring at TM≂32 K for both 57Fe as well as 119Sn‐doped samples. The local magnetic ordering shows up in the presence of a very large transferred hyperfine field of Bthf≂11.0(5) T at the 119Sn nuclei. Since such a large field is present in neither antiferromagnetic La2CuO4 superconducting La1.85Sr0.15CuO4 nor overdoped La2−xSrxCuO4 (x=0.4), the occurrence of such local spin correlations seems to be a signature of the nonsuperconducting low temperature tetragonal phase of La1.25Nd0.6Br0.15CuO4.

Calcium doping effects in57Fe : La2−x Ca x CuO4−y oxides

La2−xCaxCu0.99Fe0.01O4−y samples with 0.00 ≤x ≤ 0.30 were studied by X-ray diffraction and Mössbauer spectroscopy after heat treatment under different atmospheres (air, oxygen and helium). The variation of the relative population and the hyperfine interactions of the sites as well as the change in the lattice parameters were obtained.

Mössbauer studies of57Fe doped single crystals of GdBa2Cu3O7-δ

Abstract57Fe Mössbauer effect measurements have been performed on single crystals of57Fe doped GdBa2Cu3O7-δ at various c-axis orientations and temperatures. The analysis of the data yields information on the sign and direction of Vzz, the direction of Bhf with respect to Vzz and the anisotropy of the f-factor for the individual observed three quadrupole doublets. From these data we conclude that the quadrupole doublet with ΔEQ ≃1.9 mm/s is due to Fe on a regular Cu(1)-site (4-fold oxygen coordination) with distorted local symmetry (Vzz isnot parallel to the c-axis), while the other quadrupole doublets have higher oxygen coordinations (higher Lamb-Mössbauer-factor).