A. López

Optical and Structural Properties of Zn2TiO4:Mn2+

Polycrystalline Zn2TiO4 samples with Mn2+ doping level of 0%, 0.1%, 1.0%, and 5.0% have been produced by conventional solid-state method and their optical and structural properties investigated. Rietveld refinement of x-ray diffraction patterns revealed the formed phases and the crystallographic parameters. The chemical composition was obtained by x-ray fluorescence measurements. The optical properties were studied by photoluminescence, excitation, reflectance, and photoacoustic spectroscopy. All measurements were performed at room temperature. The photoluminescence spectrum of the pure sample (0% Mn2+) showed a band in the red region associated with Zn2TiO4, while the sample with 0.1% Mn2+ exhibited two bands, in the green and red spectral regions, assigned to Mn2+ ions at tetrahedral and octahedral sites. No emission was observed for the samples with 1.0% or 5.0% Mn2+. The excitation results for the sample with 0.1% Mn2+ ions showed characteristic peaks of Mn2+ transitions. Tanabe–Sugano theory was used to obtain the crystal field Dq, B, and C Racah parameters from the energy peak positions in the excitation spectrum of the sample with 0.1% Mn2+. Photoacoustic measurements revealed a broad band, characteristic of semiconductor materials, hiding the Mn2+ transitions.

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...