J. Fink-Finowicki

Growth conditions, structure and superconductivity of pure and metal-doped FeTe1 − xSex single crystals

Superconducting single crystals of pure FeTe1 xSex and FeTe0.65Se0.35 doped with Co, Ni, Cu, Mn, Zn, Mo, Cd, In, Pb, Hg, V, Ga, Mg, Al, Ti, Cr, Sr or Nd into Fe ions site have been grown applying Bridgmans method. It has been found that the sharpness of transition to the superconducting state in FeTe1 xSex is evidently inversely correlated with crystallographic quality of the crystals. Among all of the studied dopants only Co, Ni and Cu substitute Fe ions in FeTe0.65Se0.35 crystals. The remaining examined ions do not incorporate into the crystal structure. Nevertheless, they form inclusions together with selenium, tellurium and/or iron, what changes the chemical composition of host matrix and therefore influences Tc value. Small disorder introduced into magnetic sublattice, by partial replacement of Fe ions by slight amount of nonmagnetic ions of Cu (~ 1.5 at%) or by magnetic ions of Ni (~ 2 at%) and Co (~5 at%) with spin value different than that of Fe ion, completely suppresses superconductivity in FeTe1 xSex system. This indicates that even if superconductivity is observed in the system containing magnetic ions it can not survive when the disorder in magnetic ions sublattice is introduced, most likely because of magnetic scattering of Cooper pairs.

Growth and structural investigations of La1−xPrxGaO3 solid solution single crystals

Growth of single crystals in the pseudobinary LaGaO3-PrGaO3 system by the Czochralski and floating-zone methods was investigated. It has been found that solid solution crystals La1-xPrxGaO3 exist in the whole concentration range x, The segregation coefficients of Pr in LaGaO3 and La in PrGaO3 have been found to be k(eff)(Pr) approximate to 0.84 and k(eff)(La) approximate to 1.19. The structure of the crystals was investigated by X-ray diffraction method. With increasing Pr concentration x, the lattice parameters a and c decrease, whereas b remains almost constant, the volume of the unit-cell decreases. At x = 0.51 parameters a and b become equal and the crystal adopts a pseudo-tetragonal structure. The differential thermal analysis proved that the temperature of the first-order phase transition observed in LaGaO3 at similar to 150 degreesC rises linearly with Pr concentration I at the rate of 13.3 degreesC/Pr mol%

Giant magnetic-field changes in radio-frequency absorption in La0:67Sr0:33MnO3 near the Curie temperature

Abstract The DC transport properties of and the radio-frequency (RF) wave absorption (at 2.525 MHz ) in a sample of La0.67Sr0.33MnO3 prepared by floating-zone method are measured. The Curie temperature, Tc, of the sample is about 374 K . Giant temperature and magnetic-field variations in RF absorption are found in the vicinity of Tc. Relative change of the RF absorption in magnetic field (magnetoabsorption) is about 67% in field 2.1 kOe and about 55% in field 1 kOe . This giant magnetoabsorption effect can be used to develop RF devices controlled by temperature and low magnetic field. A weak temperature dependence of magnetoabsorption for the sample studied in the range from room temperature to about 350 K makes it especially attractive for practical use. The RF study supplemented with transport, magnetoresistive and magnetic measurements enables us to discuss the optimal properties of manganite samples for observation of giant magnetoabsorption in low field.

Influence of magnetic field on the paramagnetic-ferromagnetic transition in a La 1 − x Ca x Mn O 3 ( x ≈ 0.25 ) crystal: Ultrasonic and transport studies

The ultrasonic properties of La

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

_{1-x}

Growth and structure of SrAl0.5Ta0.5O3:LaAlO3 solid solutions single crystals

Ca

Some aspects of simultaneous stress- and field-annealing of metallic glasses

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Growth and structure of strontium-doped LaGaO3

MnO

Magnetic ordering and electrical transport in (R = Sm, Eu, Gd, Tb, Dy, Y, Bi) compounds

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An unusual field dependence of disaccomodation observed in ferromagnetic metallic glasses under stress

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