Phase separation and microwave response of epitaxial and polycrystalline manganite films

The resistance, magnetoresistance, and resistance response under microwave irradiation (f=10 and 35GHz) were measured for epitaxial and polycrystalline La 0.67 Ca 0.33 MnO 3 and La 0.67 Sr 0.33 MnO 3 thin films in the temperature range 78÷300K. The microwave induced resistance increase observed for the epitaxial films in a narrow temperature range below the ferromagnetic to paramagnetic transition temperature T c certifies coexistence of low resistance (ferromagnetic) and high resistance (paramagnetic) regions in the manganites. Resistance of polycrystalline films decreased under microwave irradiation in a wide temperature range below T c . The effect was explained in terms of microwave assisted hopping of carriers in high resistance regions formed at grain boundaries of the polycrystalline films

Chemical and Strain Engineering of Functional Oxides

International audienc

Elaboration of In2O3-ZnO Thin Films for Mid-Infrared Transparent Electrode Applications

International audienc

Preparation and properties of polycrystalline and epitaxial manganite films for pulsed magnetic field application

Deposition techniques and conditions used for preparation of thin manganite films on which bases pulsed magnetic field sensors were developed are described. High quality epitaxial and polycrystalline La0.83Sr0.17MnO3 and La0.67Ca0.33MnO3 films are prepared by pulsed liquid injection MOCVD technique and laser deposition. Possibilities to obtain variation in very wide range of electrical and magnetic properties of the films changing the deposition conditions, substrates, film structure and thickness are shown. Increase in polycrystallinity and non-homogeneity of the film’s structure leads to increase in specific resistance and decrease of the maximum temperature of ρ(T) dependence. The similar behaviour could be obtained decreasing thickness of epitaxial film down to several nanometres. Magnetoresistance MR of films prepared by different techniques and at different conditions was investigated at pulsed magnetic fields up to 35 T. The obtained results showed that polycrystalline films have several advantages in comparison with epitaxial ones for the development of pulsed magnetic field sensors. In spite of lower MR sensitivity, polycrystalline films have no MR saturation effects in high magnetic fields and can be successfully used to measure absolute value of the fields up to 35 T

Phase Separation and Microwave Response of Epitaxial and Polycrystalline Manganite Films

The resistance, magnetoresistance, and resistance response under microwave irradiation (f=10 and 35GHz) were measured for epitaxial and polycrystalline La 0.67 Ca 0.33 MnO 3 and La 0.67 Sr 0.33 MnO 3 thin films in the temperature range 78÷300K. The microwave induced resistance increase observed for the epitaxial films in a narrow temperature range below the ferromagnetic to paramagnetic transition temperature T c certifies coexistence of low resistance (ferromagnetic) and high resistance (paramagnetic) regions in the manganites. Resistance of polycrystalline films decreased under microwave irradiation in a wide temperature range below T c . The effect was explained in terms of microwave assisted hopping of carriers in high resistance regions formed at grain boundaries of the polycrystalline films

Investigation of Optically Modified YBa2Cu3O7–x Films by Means of X-ray Microanalysis Technique

<p>This work reports on investigation of remnant oxygen content in optically-modified regions of 0.3-mm-thick YBa₂Cu₃O_{7–<em>x</em>} films, patterned by a laser-writing technique in an inert ambient gas atmosphere at room temperature. A laser-treated region of weak superconductivity with dimensions depending on the size of a laser spot, laser power, and initial content of oxygen is characterized by a lower oxygen content, weaker critical magnetic field, and suppressed both the superconducting critical temperature and the critical current density, as compared to the laser untreated regions. Optically induced (cw-laser, <br /> 532-nm-wavelength) heating strongly affects a non-uniform distribution of remnant oxygen content in the film, depending both on the optical power and beam’s scanning velocity. A level of oxygen depletion and the size of the oxygen-deficient region have been directly estimated from scanning-electron-microscope spectra with the X-ray microanalysis technique. The results of our measurements were compared with results extracted from electric measurements, assuming a correlation between the remnant oxygen content and the electric transport properties of oxygen-deficient YBa₂Cu₃O_{7–<em>x</em>} films.</p> <p>DOI: <a href="http://dx.doi.org/10.5755/j01.ms.20.2.6323">http://dx.doi.org/10.5755/j01.ms.20.2.6323</a></p

Ferroelectric PbTiO3 films grown by pulsed liquid injection metalorganic chemical vapour deposition

International audienceThe influence of various deposition conditions (deposition temperature, partial oxygen pressure and solution composition) to the growth of ferroelectric PbTiO3 (PTO) films by pulsed liquid injection metalorganic chemical vapour deposition (MOCVD) was examined. Films were grown on LaAlO3 (001), SrTiO3 (001) and sapphire (R-plane) substrates. Pb(thd)2 and Ti(OiPr)2(thd)2 (thd = 2,2,6,6-tetramethyl-3,5-heptanedionate) dissolved in toluene were used as precursors. The evolution of film composition, surface morphology and microstructure with deposition conditions was studied. The film microstructure was characterized by X-ray diffraction (XRD) in Bragg-Brentano and Schulz geometries and by Raman spectroscopy. Epitaxial films on perovskite substrates consisted of dominant c-axis and minor a-axis textured zones (c-domains and a-domains). The amount of a-domains in films depended mainly on deposition temperature. The twinning in a- and c-domains was observed and twinning (tilt) angles depended on deposition conditions and substrate. Fully twinned or partially twinned films were obtained in varying deposition conditions. The best quality epitaxial films were obtained on SrTiO3 and LaAlO3 at 650 °C. Films on sapphire were mainly polycrystalline

Current-voltage dependences of YBa2Cu3O7-d superconducting thin films with laser-written channel of easy vortex motion

KTB virsmo metu, atsitiktinėse kanalo vietose susikuria magnetinių sūkurių-antisūkurių poros, kurias atskyrus jų sūkuriai ir antisūkuriai juda link darinio karštų ir ten anihiliuoja su savo magnetiniais antipodais. Prielaidai dėl KTB vyksmo deguonimi nuskurdintame kanale neprieštarauja ir YBCO darinio I-V charakteristikų matavimai esant išoriniam magnetiniam laukui. KTB virsmu paaiškintas superlaidžiojo darinio elektrinės „varžos“ (srovės disipacijos) mažėjimas, didinant išorinį magnetinį lauką. Išoriniam magnetiniam laukui viršijus dariniu tekančios elektros srovės kuriamą magnetinį lauką, sūkurių-antisūkurių anihiliacijos linija pasislenka už superlaidžiojo darinio krašto. Todėl magnetinių sūkurių judėjimo sąlygota darinio elektrinė varža šuoliškai padidėja beveik du kartus, o I-V charakteristikose įtampos „laipteliai“ tampa neryškūs. Šis eksperimentinis darbas atskleidžia galimybes magnetinių sūkurių judėjimą superlaidininke valdyti elektros srove, temperatūra ir išoriniu magnetiniu lauku

Easy vortex motion in an artificial channel of YBa2Cu3O7-δ superconducting films

Quasi-Josephson effect produced by a coherent vortex motion in the horizontal part of the laser-performed Π-shaped channel of a YBa2Cu3O7-δ superconducting bridge was investigated by means of electric transport measurements. We observed that in our structures, in a limited range of temperatures and bias currents, the vortices were confined in the channel only and moved coherently with the velocity of 3 × 104 m/s. The corresponding current-voltage characteristics of the bridge exhibited Josephson-like voltage steps with the amplitude dependent on temperature, but independent of the bias current