The resistive switching characteristics of Pr0.7Ca0.3MnO3 (PCMO) thin films deposited on LaNiO3 (LNO)-electrodized Si substrate were investigated. Highly (100)-textured PCMO films were grown on the (100)-oriented LNO electrode. They exhibited reversible and steady bistable resistance switching behavior. The resistive switching behavior of PCMO capacitors on LNO is related to the trap-controlled space charge limited current mechanism and LNO/PCMO/LNO capacitor exhibits the strongest resistive switching effect with a resistance ratio for about two orders of magnitude.

The magnetotransport properties of La0.75Sr0.25MnO3 (LSMO) films epitaxially grown on SrTiO3 (0 0 1) substrate were studied. The Curie temperature (Tc) of LSMO films decreases from 300 to 105 K with a reduction in the film thickness to 5 nm. A clear metal–insulator transition is observed at a temperature consistent with Tc for films thicker than 10 nm. However, the 5 nm thick film displays an insulative characteristic along with a high magnetoresistence effect in a wide range of temperatures below and above Tc. A phase-separation phenomenon in the 5 nm thick film was demonstrated by thermally activated hopping transport between ferromagnetic metallic domains embedded in an insulative matrix at temperatures below Tc, but between paramagnetic metallic domains at temperatures above Tc. It was also confirmed by conductive atomic force microscopy images.

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In this study, we have fabricated (00l)-oriented Pb(Zr0.5Ti0.5)O3∕CoFe2O4∕Pb(Zr0.5Ti0.5)O3 (PZT/CFO/PZT) trilayer thin films on LaNiO3 coated substrates by dual-cathode rf sputtering system. The thicknesses of top and bottom PZT thin films were fixed at 100nm but those of the CFO interlayer were 40, 80, and 120nm, respectively. The x-ray diffraction showed well-defined PZT and CFO peaks with (00l) orientation, and large grains with columnar structure were observed by field-emission scanning electron microscopy. Hard-magnetic M-H loop with a saturation magnetization of ∼235emu∕cm3 and ferroelectric hysteresis curve with saturation polarization of ∼40.1μC∕cm2 were measured at room temperature for the PZT/CFO (120 nm)/PZT trilayer thin films. Due to the low-resistance CFO interlayer in series with the PZT layers, the ferroelectric property does not significantly vary with the CFO interlayer thickness. In contrast, the possibility of the existence of nonmagnetic interfacial layer at the CFO/PZT interface causes the reduction of the magnetization. Both of the good magnetic and ferroelectric responses suggest that the (00l)-oriented PZT/CFO/PZT trilayer thin film is a promising magnetoeletric material for study.

The magnetic properties of Pb(Zr0.5Ti0.5)O3∕La0.9Sr0.1MnO3 bilayers epitaxially grown on Nb-doped SrTiO3 (001) substrate were studied. Bilayers with a fixed Pb(Zr0.5Ti0.5)O3 (PZT) layer thickness of 200nm and different La1−xSrxMnO3 layer thicknesses varying from 10to40nm show a divergence between field-cooled (FC) and zero-field-cooled (ZFC) temperature-dependent magnetization measurements. Moreover, the polarization state of the PZT ferroelectric layer induces a spin-pinning effect causing a variation of the M∕M(10K) ratio in ZFC measurement and the divergent temperature (Td) between FC and ZFC processes. The magnetic hysteresis loops measured in FC and ZFC processes confirm the spin-pinning effect induced from the ferroelectric polarization field, leading to an alternation of the hysteresis loop characteristics for samples polarized with different signs of voltage.

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The strain effect on the magnetotransport properties in La0.9Sr0.1MnO3 films epitaxially deposited on SrTiO3 (STO) and LaAlO3 (LAO) substrates, is demonstrated. Large compressive strain is formed in the films on the LAO substrate; however, that on the STO is subject to a small tensile strain. Strain relaxation of films grown on both substrates results in the formation of a spin-canted antiferromagnetic (AFM) insulative phase, causing the increase in resistivity with decreasing temperature. The characteristics of the AFM insulative phase become apparent with increasing film thickness, which leads to a clear AFM transition in the films grown on LAO and a reduction of magnetization and Curie temperature in those on STO. The magnetoresistance effect of the films is also consistent with the above results.

The top-configuration Co(y)/IrMn(90 Å) exchange-biasing phenomenon has been studied by sputtering method with two conditions: (a) the substrate temperature (T s ) was kept at room temperature (RT) only, and (b) T s = RT with an in-plane field (h) = 500 Oe deposition and postdeposition annealing in the field at T A = 250 °C for 1 h, with the samples field cooled to RT. High resolution electron cross-sectional transmission electron microscopy (HR X-TEM) reveals that the IrMn (111) texturing plays a main role to exchange-biasing field (H ex ) and interfacial energy (J k ). The H ex versus y result shows that H ex increases when y decreases in case (b). Since J k = H ex M s y, where M s is Co magnetization, it is easy to derive H ex = J k /(M s y). Therefore, if H ex is inversely proportional to y, with J k /M s constant, we find H ex y = constant. In case (a), H ex is very small in general, while in case (b), H ex is of the order of 60-180 Oe. Moreover, the y dependence of J k is similar to that of M s for each curve. Finally, the H c is inversely proportional to y because of the surface pinning effects from the Ta/Co and Co/IrMn interfaces.