Investigation of Phase Transition inLa1–xPrxGaO3 and La1–xNdxGaO3 Crystals

The solid solution crystals, La_1–xNd_xGaO₃ and La_1–xPr_xGaO₃ have been studied by differential scanning calorimetry method; the crystals exhibit the first order phase transition, the temperature of the transition linearly increases with the concentration of Pr or Nd. The structure of the crystals has been determined by X-ray diffraction. The correlation between the phase transition temperature and crystalline structure at the temperature of the phase transition in both solid solution families is discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Magnetic anisotropy in geometrically frustrated kagome staircase lattices

This paper reviews experimental results concerning magnetic anisotropy in geometrically frustrated kagome staircase lattices. Following problems are discussed: high-temperature susceptibility measurements of kagome single crystals; inelastic neutron scattering measurements on Co₃V₂O₈ single crystals; EPR of Co²⁺ ions in kagome staircase Mg₃V₂O₈ single crystals. The single-ion anisotropy Hamiltonian is used to analyze experimental results. It is suggested that the magnetic anisotropy in kagome staircase M₃V₂O₈ (M=Co, Ni, Mn) oxides has mainly single-ion origin.     

Pressure-induced enhancement of the superconducting properties of single-crystalline FeTe0.5Se0.5

The pressure dependence, up to 11.3 kbar, of basic parameters of the superconducting state, such as the critical temperature (T(c)), the lower and the upper critical fields, the coherence length, the penetration depth, and their anisotropy, was determined from magnetic measurements performed for two single-crystalline samples of FeTe(0.5)Se(0.5). We have found pressure-induced enhancement of all of the superconducting state properties, which entails a growth of the density of superconducting carriers. However, we noticed a more pronounced increase in the superconducting carrier density under pressure than that in the critical temperature which may indicate an appearance of a mechanism limiting the increase of T(c) with pressure. We have observed that the critical current density increases under pressure by at least one order of magnitude.     

Spectroscopic characterization of a Tm3+:SrGdGa3O7 crystal

3 O₇ crystal have been recorded at room temperature and at approximately 8 K. Room-temperature luminescence lifetimes of ¹D₂, ¹G₄, ³H₄, and ³F₄ states have been measured for Tm concentration ranging from [%at.]0.5 to [%at.]9. Based upon these data the crystal field splitting of luminescent states has been derived and radiative transitions rates have been evaluated. Strong self-quenching of luminescence originating in the ¹G₄ and ³H₄ states has been found in this activator–host combination. Peak emission cross section of the potential laser transition at 1800 nm was determined to be 3.9×10^-21 cm² and the gain coefficient versus wavelength was estimated and discussed. Received: 14 April 1998/Revised version: 10 August 1998     

Geometrically frustrated Kagome staircase lattice with chemical disorder

The effect of nonmagnetic Mg²⁺ and magnetic Co²⁺ doping in Kagome staircase compounds was investigated using DC magnetic susceptibility. The main effect of doping is to change effective anisotropy of the Ni₃V₂O₈ and Co₃V₂O₈ crystals. It has a considerable effect on magnetic field induced phase transitions in both kinds of crystals. The doping has also an effect on the Dzyaloshinskii–Moriya exchange interactions. In some cases the doping enhances this interaction while in another it suppresses it completely.