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Abstract: Room temperature57Fe Mssbauer effect spectra of several Al-TM-Fe icosahedral quasicrystals are reported. Results of fits to discrete sites and to various distributions of quadrupole splittings are presented. Mean isomer shifts, $$\overline \delta $$ , and quadrupole splittings, Δ, are shown to be insensitive to the fitting procedure used. Trends in $$\overline \delta $$ and $$\overline \Delta $$ for the icosahedral phase may be indicative of a Hume-Rothery stabilization mechanism.

Abstract: Zeeman splitting of Mossbauer spectra of57Co doped into Eu2CuO4 and Gd2CuO4 indicates magnetic ordering of Cu moments for temperatures below about 150 K in Eu2CuO4 and below about 200 K in Gd2CuO4.

Results of TDPAC and Mössbauer measurements of hyperfine magnetic fields in L21 Heusler alloys X2MnZ are given. TDPAC utilized Cd-111 from In-111 at the Z site and Ag-111 at the X site, and Ru-99 from Rh-99 at the X site. Mössbauer studies utilized Sn-119 at the Z site or at the Mn site. A compilation of hmf values is presented, and estimates of the polarized electron density are given for 1 nn, 2 nn, and 3 nn of the Mn ions in these alloys.

Hmf values are reported for Fe-57 in Ni2MnGa, and for Cd-111, Fe-57, and Sn-119 in Pd2MnSn and Ru2FeSn.

The systematics of hyperfine magnetic fields at sp impurities on the Z-sites in Co based Heusler alloys are investigated. New TDPAC measurements of Cd hyperfine fields are reported.

We have investigated the systematics of hyperfine magnetic field on a fixed probe at the Z-site in Heusler alloys Rh2MnZ as the valence of Z (sp element) is varied. The hmf on119Sn in Rh2MnIn.98119Sn02 has been measured at 293K and 77K. In Rh2Mn1.12Sb.86119Sn.02 the hmf on121Sb has been measured at 77 K, and on119Sn at 293 K and 77 K. The results are compared with the hmf on119Sn in Rh2Mn Ge.98119Sn.02 Rh2Mn Sn, and Rh2Mn Pb.98119Sn.02.

Icosahedral Al86Fe14 has been prepared by rapid quenching from the melt. Mössbauer effect spectra are quadrupole split doublets. The temperature dependence of the isomer shift is consistent with the second order doppler shift and the quadrupole splitting decreases linearly with temperature.

Abstract: The time differential perturbed angular correlation method has been used to measure, as a function of temperature, the hyperfine magnetic field at Cd sites in the Heusler alloys Co2MnZ (Z=Si, Ga, Ge, Sn). The hyperfine fields, normalized to the total magnetic moment per formula unit, show an approximately linear trend toward more positive values with increasing lattice parameter.

SrxCa1−xCu0.9957Fe0.01O2 was studied forx=0.13, 0.15, and 0.17. Mössbauer spectroscopy and magnetization measurements indicate magnetic ordering characteristic of spin glass systems withTf∼70K forx=0.15 and 0.13.

Abstract: Mssbauer effect studies of57Co-doped La2CuO4−y were performed at temperatures between 4.2 K and room temperature. These confirm the antiferromagnetic ordering of these compounds below room temperature. Temperature dependence of the quadrupole splitting shows that the hyperfine field is at an angle with thec-axis.

Abstract: Mssbauer spectra of57Co-doped polycrystalline or single-crystal samples of layered perovskites La2Mo4 (M=Cu, Co, Ni) and R2CuO4 (R=Nd, Eu, Gd) were recorded at room temperature and below. Of the samples studied, only La2CuO4 shows a widely separated doublet at room temperature and a single clearly resolved sextet well belowT N.

Abstract: Split source57Fe Mssbauer effect spectroscopy has been performed between 4 K and 295 K on the superconducting perovskite GdBa2Cu3O7−y. No evidence is seen for magnetic splitting at low temperatures as reported in some split absorder57Fe Mssbauer experiments on this material. There is evidence for phonon mode softening, as observed for119Sn Mssbauer spectra of some other highT c superconductors.