J. Sacanell

Magnetoresistive memory in phase-separated La0.5Ca0.5MnO3

Abstract We have studied a non-volatile memory effect in the mixed valent compound La 0.5 Ca 0.5 MnO 3 induced by magnetic field ( H ). In a previous work (Phys. Rev. B 65 (2002) 104403), it has been shown that the response of this system upon application of H strongly depends on the temperature range, related to three well-differentiated regimes of phase separation occurring below 220xa0K. In this work we compare memory capabilities of the compound, determined following two different experimental procedures for applying H , namely zero-field cooling and field cooling the sample. These results are analyzed and discussed within the scenario of phase separation.

Correlation between magnetic and transport properties of phase-separated La0.5Ca0.5MnO3

Abstract The effect of low-magnetic fields on the magnetic and electrical transport properties of polycrystalline samples of the phase-separated compound La0.5Ca0.5MnO3 is studied. The results are interpreted in the framework of the field-induced ferromagnetic fraction enlargement mechanism. A fraction expansion coefficient αf, which relates the ferromagnetic fraction f with the applied field H, was obtained. A phenomenological model to understand the enlargement mechanism is worked out.

Persistent magnetoresistive memory in phase separated manganites

Abstract We have studied magnetic and transport properties on different manganese-oxide-based compounds exhibiting phase separation: polycrystalline La 5/8− y Pr y Ca 3/8 MnO 3 ( y =0.3) and La 1/2 Ca 1/2 Mn 1− z Fe z O 3 ( z =0.05), and single crystals of La 5/8− y Pr y Ca 3/8 MnO 3 ( y ∼0.35). Time dependent effects indicate that the fractions of the coexisting phases are dynamically changing in a definite temperature range. We found that in this range the ferromagnetic fraction “ f ” can be easily tuned by application of low magnetic fields ( f ” and can be recovered through transport measurements. This effect is due both to the existence of a true phase separated equilibrium state with definite equilibrium fraction “ f 0 ”, and to the slow growth dynamics. The fact that the same global features were found on different compounds and in polycrystalline and single crystalline samples, suggests that the effect is a general feature of some phase separated media.

Direct observation of magnetocaloric effect by differential thermal analysis: Influence of experimental parameters

Abstract The magnetocaloric effect is the isothermal change of magnetic entropy and the adiabatic temperature change induced in a magnetic material when an external magnetic field is applied. In this work, we present an experimental setup to study this effect in metamagnetic transitions, using the differential thermal analysis technique, which consists in measuring simultaneously the temperatures of the sample of interest and a reference one while an external magnetic field ramp is applied. We have tested our system to measure the magnetocaloric effect in La0.305Pr0.32Ca0.375MnO3, which presents phase separation effects at low temperatures (T

Correlation between electrical and magnetic properties of phase-separated manganites studied with a general effective medium model

Abstract We have performed electrical resistivity and DC magnetization measurements as a function of temperature, on polycrystalline samples of phase-separated La5/8−yPryCa3/8MnO3 (y=0.3). We have used the general effective medium theory to obtain theoretical resistivity vs. temperature curves corresponding to different fixed ferromagnetic (FM) volume fraction values, assuming that the sample is a mixture of typical metallic-like and insulating manganites. By comparing this data with our experimental resistivity curves we have obtained the relative FM volume fraction of our sample as a function of temperature. This result matches with the corresponding magnetization data in excellent agreement, showing that a mixed-phase scenario is the key element to explain both the magnetic and transport properties in the present compound.

Thermal cycling effects on static and dynamic properties of a phase separated manganite

Abstract In this work we address the interplay between two phenomena which are signatures of the out-of-equilibrium state in phase separated manganites: irreversibility against thermal cycling and aging/rejuvenation process. The sample investigated is La0.5Ca0.5MnO3, a prototypical manganite exhibiting phase separation. Two regimes for isothermal relaxation were observed according to the temperature range: for Tu202f>u202f100u202fK, aging/rejuvenation effects are observed, while for T

Nanostructured LnBaCo2O6−𝜹 (Ln = Sm, Gd) with layered structure for intermediate temperature solid oxide fuel cell cathodes

In this work, we present the combination of two characteristics that are beneficial for solid oxide fuel cell (SOFC) cathodic performance in one material. We developed and evaluated for the first time nanostructured layered perovskites of formulae LnBaCo2O6-d with Ln = Sm and Gd (SBCO and GBCO, respectively) as SOFC cathodes, finding promising electrochemical properties in the intermediate temperature range. We obtained those nanostructures by using porous templates to confine the chemical reagents in regions of 200-800 nm. The performance of nanostructured SBCO and GBCO cathodes was analyzed by electrochemical impedance spectroscopy technique under different operating conditions using Gd2O3-doped CeO2 as electrolyte. We found that SBCO cathodes displayed lower area-specific resistance than GBCO ones, because bulk diffusion of oxide ions is enhanced in the former. We also found that cathodes synthesized using smaller template pores exhibited better performance.

Magnetoresistive memory in phase separated La

Abstract We have studied a non-volatile memory effect in the mixed valent compound La 0.5 Ca 0.5 MnO 3 induced by magnetic field ( H ). In a previous work (Phys. Rev. B 65 (2002) 104403), it has been shown that the response of this system upon application of H strongly depends on the temperature range, related to three well-differentiated regimes of phase separation occurring below 220xa0K. In this work we compare memory capabilities of the compound, determined following two different experimental procedures for applying H , namely zero-field cooling and field cooling the sample. These results are analyzed and discussed within the scenario of phase separation.

_{0.5}

Abstract We have studied a non-volatile memory effect in the mixed valent compound La 0.5 Ca 0.5 MnO 3 induced by magnetic field ( H ). In a previous work (Phys. Rev. B 65 (2002) 104403), it has been shown that the response of this system upon application of H strongly depends on the temperature range, related to three well-differentiated regimes of phase separation occurring below 220xa0K. In this work we compare memory capabilities of the compound, determined following two different experimental procedures for applying H , namely zero-field cooling and field cooling the sample. These results are analyzed and discussed within the scenario of phase separation.

Ca

Abstract We have studied a non-volatile memory effect in the mixed valent compound La 0.5 Ca 0.5 MnO 3 induced by magnetic field ( H ). In a previous work (Phys. Rev. B 65 (2002) 104403), it has been shown that the response of this system upon application of H strongly depends on the temperature range, related to three well-differentiated regimes of phase separation occurring below 220xa0K. In this work we compare memory capabilities of the compound, determined following two different experimental procedures for applying H , namely zero-field cooling and field cooling the sample. These results are analyzed and discussed within the scenario of phase separation.