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3 Acta Physica Polonica A

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Thermal Fluctuations in YBCO Thin Film on MgO Substrate

100%

Chrobak M. , Woch W. , Szwachta G. , Zalecki R. , Gondek Ł. , Kołodziejczyk A. , Kusiński J.

Acta Physica Polonica A

2014

tom 126

nr 4a

A-88-A-92

The c-axis orientation YBa_2Cu_3O_δ thin film was prepared directly on MgO substrate by the pulse laser deposition. The thickness of the film was 170 nm. The superconducting critical temperature was T_{c50%}=89 K and the width of superconducting transition was Δ T= 1.6 K. Temperature dependence of the critical current of the film was obtained from the temperature dependences of the imaginary part of the AC susceptibility using the Bean model. The critical current density was J_{c}=1.2×10^7 A/cm^{2} at 77 K in the self field. The critical exponents were calculated for several values of the DC applied magnetic field using the temperature dependences of magnetoresistivity. The thermal fluctuations in vicinity of the critical temperature were analysed.

Structure and Magnetism of LSMO/BTO/MgO/LSMO Multilayers

100%

Pawlak J. , Żywczak A. , Szwachta G. , Kanak J. , Gajewska M. , Przybylski M.

Acta Physica Polonica A

2018

tom 133

nr 3

548-551

A multiferroic tunnel junction (MFTJ) is a promising device for future memory systems with discrete and different logic states which are controlled by a combination of electric and magnetic fields. The goal of ongoing research is to present ferroelectric and ferromagnetic properties, especially at room temperature (RT), represented as high values of tunnel electroresistance (TER) and tunnel magnetoresistance (TMR). A key aspect is the appropriate preparation of a sample allowing epitaxial growth. The thin layers were prepared by pulsed laser deposition on atomically smooth monocrystalline SrTiO₃ (STO) substrates. The ferromagnetic metal layers La_{0.67}Sr_{0.33}MnO₃ (LSMO) are separated by a layer of a ferroelectric insulator - BaTiO₃ (BTO). The same structure of LSMO, BTO and STO (perovskite) and a similar lattice constant make it possible to obtain high-quality heterostructures. Magnetic measurements confirm differences in the magnetic coercivity of the top and bottom LSMO layer, which allows to obtain their parallel and antiparallel magnetization orientation. A modification of the interfaces of BTO by thin MgO layer enables an increase in the value of the TER effect.

Magnetoresistance Study of c-Axis Oriented YBCO Thin Film

84%

Chrobak M. , Woch W. , Kowalik M. , Zalecki R. , Giebułtowski M. , Przewoźnik J. , Kapusta C. , Szwachta G.

Acta Physica Polonica A

2017

tom 131

nr 4

1018-1020

The c-axis orientation YBa₂Cu₃O_δ thin film was prepared directly on MgO substrate by the pulse laser deposition. The thickness of the film is 170 nm. The superconducting critical temperature is T_{c50%}=87.5 K and the width of superconducting transition is ΔT = 1.8 K. The temperature dependences of magnetoresistance were measured up to 90 kOe. The widths of the transition to the superconducting state versus applied magnetic field were derived and they were fitted using the formula: Δ T=CH^m +Δ T₀. The irreversibility fields as a function of temperature were obtained and fitted by the de Almeida and Thouless-like equation: H_{irr}=H_{irr0}(1-T/T_{c0})^n. The irreversibility field at the liquid nitrogen temperature was calculated and it is H_{irr}=43.8 kOe when the applied magnetic field is parallel to the c-axis.