Lattice structure and magnetization of LaCoO3 thin films

We investigate the structure and magnetic properties of thin films of the LaCoO$_{3}$ compound. Thin films are deposited by pulsed laser deposition on various substrates in order to tune the strain from compressive to tensile. Single-phase (001) oriented LaCoO$_{3}$ layers were grown on all substrates despite large misfits. The tetragonal distortion of the films covers a wide range from -2% to 2.8%. Our LaCoO$_{3}$ films are ferromagnetic with Curie temperature around 85 K, contrary to the bulk. The total magnetic moment is below $1\mu_{B}$/Co$^{3+}$, a value relatively small for an exited spin-state of the Co$^{3+}$ ions, but comparable to values reported in literature. A correlation of strain states and magnetic moment of Co$^{3+}$ ions in LaCoO$_{3}$ thin films is observed.Comment: submitted tu European Phys. J.

The identity and cultural stereotypes during the individual and state-preservation: between past and future

Ми розглядаємо питання розуміння ідентичності як механізму самовизначення в навколишній дійсності. Ідентичність продовжують розуміти як гнучкий та схильний до розвитку процес самоототожнення будь- чого з аналізом власного «Я». Ідентичність – це певний ідеальний образ, стандарт, до якого скеровано зусилля та рух кожного індивіду. Процес формування ідентичності досить складний і може створюватися викривлена модель ідентичності. У процесі створення власної ідентичності індивід може звертатися як до реальних, так й уявних категорій. Саме на перетині уявного й маскується місце для негативної дії амбітних політичних технологій із заміни та знищення реальних умов для здорової особистості з цілісною ідентичністю. Дослідженням продовжуємо стверджувати наявність в ідентичності унікальної концентрації, співвідношення між намаганням бути «подібним», «відповідним» із протилежним рухом до «знаковості» та «унікальності».The article is devoted to the problem of understanding identity as self-determination in the surrounding world. Identity is understood as a flexible and developing process of self-identification, i.e. of correlation of something there is with yourself. We are considering the question of understanding identity as a mechanism of self determination in the surrounding reality. The identity continues to be understood as flexible and subject to the same process of identification of any of the analysis of his own “I”. Identity is a perfect image, the standard to which directed efforts and movement of each individual. The formation of identity is rather complicated, and can create curved model identity. In the process of creating its own identity individual can apply to both real, and imaginary categories. It is at the intersection of imaginary and masked the negative impact location for ambitious political technologies for replacement and destruction of real conditions for a healthy individual with integral identity. The study goes on to say in the presence of a unique identity concentration ratio between attempts to be “similar”, “appropriate” with the opposite movement to “the token” and “uniqueness”

Enhancement of switching speed of BiFeO3 capacitors by magnetic fields

The effect of a magnetic field on the ferroelectric switching kinetics of BiFeO3 (BFO) capacitors with La0.8Ca0.2MnO3 (LCMO) bottom electrode and Pt top contact has been investigated. We find a strong dependence of the remnant polarization and coercive field on the magnetic field. The switching time can be systematically tuned by magnetic field and reaches a tenfold reduction around the Curie temperature of LCMO at 4 T. We attribute this behavior to the splitting of the voltage drops across the BFO film and the LCMO bottom electrode, which can be strongly influenced by an external magnetic field due to the magnetoresistance. Further experiments on the BFO capacitors with SrRuO3 bottom electrodes show little magnetic field dependence of ferroelectric switching confirming our interpretation. Our results provide an efficient route to control the ferroelectric switching speed through the magnetic field, implying potential application in multifunctional devices

Thermal generation of spin current in epitaxial CoFe2O4 thin films

The longitudinal spin Seebeck effect (LSSE) has been investigated in high-quality epitaxial CoFe2O4 (CFO) thin films. The thermally excited spin currents in the CFO films are electrically detected in adjacent Pt layers due to the inverse spin Hall effect (ISHE). The LSSE signal exhibits a linear increase with increasing temperature gradient, yielding a LSSE coefficient of ~100 nV/K at room temperature. The temperature dependence of the LSSE is investigated from room temperature down to 30 K, showing a significant reduction at low temperatures, revealing that the total amount of thermally generated magnons decreases. Furthermore, we demonstrate that the spin Seebeck effect is an effective tool to study the magnetic anisotropy induced by epitaxial strain, especially in ultrathin films with low magnetic moments.Comment: 17 pages, 4 figure

Strain-induced insulator state in La_0.7Sr_0.3CoO_3

We report on the observation of a strain-induced insulator state in ferromagnetic La_0.7Sr_0.3CoO_3 films. Tensile strain above 1% is found to enhance the resistivity by several orders of magnitude. Reversible strain of 0.15% applied using a piezoelectric substrate triggers huge resistance modulations, including a change by a factor of 10 in the paramagnetic regime at 300 K. However, below the ferromagnetic ordering temperature, the magnetization data indicate weak dependence on strain for the spin state of the Co ions. We interpret the changes observed in the transport properties in terms of a strain-induced splitting of the Co e_g levels and reduced double exchange, combined with a percolation-type conduction in an electronic cluster state