Sherif Yehia

Antiferromagnetism in 57Co-doped La2CuO4-y studied by Mossbauer spectroscopy

Mössbauer 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.

Hyperfine magnetic field measurements in Heusler alloys Ni2MnGa, Pd2MnSn, and Ru2FeSn

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

Mossbauer studies of 57Co-doped layered perovskites

Mössbauer 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 belowTN.

TDPAC and Mossbauer measurements of hyperfine fields in chromium-based chalcogenide spinels

Hyperfine magnetic fields are measured at Cd-111 and Sn-119 in CdCr2Se4 and CuCr2Se4, as well as at Cd-111 in CdCr2S4 and CuCr2S4. Quadrupole frequencies are measured for Cd-111 in CdCr2S4 and CdCrvSe4 above Tc.

Hyperfine Magnetic-Fields at Sp-Sites in Co2yz Heusler Alloys

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.

Fe-57 and Sn-119 Mossbauer study of La2CuO4-y, YBa2Cu3O7-y and SmBa2Cu3O7-y

Abstract Mossbauer studies revela antiferromagnetic order in doped La2CuO4−y; at 77 K, H=476 kOe at Fe-57 and H⩽10kOe at Sn-119. Split-source and conventional absorber experiments on RBa2Cu3O7-y (R=Y, Sm) are consistent with occupation of 3 sites by Fe-57, the relative population depending on sample preparation and Fe concentration.

Mössbauer measurement of the hyperfine magnetic field AT sp site in Heusler alloys Rh2 Mn Z (Z=In and Sb)

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.

Hyperfine magnetic field on Cd-111 in heusler alloys Co2MnZ (Z=Si, Ga, Ge, Sn)

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.