A systematic study is presented for structural characterization and physical properties of two kinds of perovskite oxide superlattices composed of ferromagnetic (FM) and antiferromagnetic (AF) layers. Spin ordering structures is modulated in FM La0.6Sr0.4MnO3/G-type AF La0.6Sr0.4FeO3 superlattices, whereas, ordering structures both in spin and orbital are modulated in La0.6Sr0.4MnO3/A-type AF La0.45Sr0.55MnO3 along the growth directions. Large magnetoresistance subsists down to low temperature in La0.6Sr0.4MnO3/La0.6Sr0.4 Fe3 (F/G) superlattices as a result of recovery of ferromagnetism, which is once suppressed by spin frustration at the interface between FM and G-type AF layers. In contrast, the constituent layers in the La0.6Sr0.4MnO3/La0.45Sr0.55MnO3 (F/A) superlattices appear to keep their ground states due to the absence of spin frustration at the interface. Magnetoresistance is pronounced in this type of superlattices at low temperatures when the AF layer is very thin, indicating restoration of the electronic coupling between the neighboring FM layers which are otherwise decoupled by intervening A-type AF spin ordering and dx2−y2 orbital ordering in La0.45Sr0.55MnO3 layers.

We compare the magnetization versus temperature, determined by magnetic circular dichroism, with bulk magnetization determined by SQUID magnetometry. The results for two different manganese perovskites, La0.65A0.35MnO3 systems (A=Pb, Sr), epitaxially grown on LaAlO3 substrates compared. The results suggest that the magnetic circular dichroism results may not be representative of the bulk magnetization. Similar materials, but with a different secondary electron mean free path lengths or different surface compositions, may thus be expected to have different behavior in MCD or MXLD that depends on a photoyield for detection.

A spin-glass state up to 210 K has been found in (Mg,Fe){Mg,Fe,Ti)2O4 spinel ferrite thin films formed on α-Al2O3(0001) substrates. The long-time relaxation of the magnetization in zero-field-cooled operation, which is characteristic feature of the spin-glass state, has been observed below 210 K. We have also achieved the change of magnetic state in the film from spin-glass to ferrimagnet over a wide temperature range below 160 K by means of light-irradiation. The amount of spin-melt on light-irradiation is calculated to be 41 % at 10 K and 26 % at 100 K.

Colossal magnetoresistive (CMR) manganites display a spectacular range of structural, magnetic, and electronic phases as a function of hole concentration, temperature, magnetic field, etc. Although the bulk of research has concentrated on the 3-D perovskite manganites, the ability to study anisotropic magnetic and electronic interactions made available in reduced dimensions has accelerated interest in the layered Ruddlesden-Popper (R-P) phases of the manganite class. The quest for understanding the coupling among lattice, spin, and electronic degrees of freedom (and dimensionality) is driven by the availability of high quality materials. In this talk, we will present recent results on synthesis and magnetic properties of layered manganites from the La2−2xSr1+2xMn2O7 series in the Mn4+-rich regime x > 0.5. This region of the composition diagram is populated by antiferromagnetic structures that evolve from the A-type layered order to G-type “rocksalt” order as x increases. Between these two regimes is a wide region (0.7 < x < 0.9) where an incommensurate magnetic structure is observed. The IC structure joins spin canting and phase separation as a mode for mixed-valent manganites to accommodate FM/AF competition. Transport in these materials is dominated by highly insulating behavior, although a region close to x = 0.5 exhibits metal-nonmetal transitions and an extreme sensitivity to oxygen content. We suggest two possible explanations for this transport behavior at doping just above x=0.5: localization by oxygen defects or charge ordering of Mn3+/Mn4+ sites.

The quasi binary systems LaMnO3 – SrMnO3 and LaMnO3 – CaMnO3 have been studied. Both systems show a miscibility gap below about 1400°C in air. This phenomenon causes the decomposition of single phase (La,Sr)MnO3−x and (La,Ca)MnO3−x solid solution with intermediate La:Sr or La:Ca ratios into La rich SrMnO3−x or CaMnO3−x and Sr or Ca rich LaMnO3−x at lower temperatures. At 1400°C a structure transformation of (La,Sr)MnO3 from orthorhombic to rombohedral has not been observed and the structure of La0.7Sr0.3MnO3 has been determined to be orthorhombic with a = 0.54927 ± 0.0009 nm, b = 0.54582 ± 0.0009 nm, and c = 0.76772 ± 0.0034 nm.

We have studied magnetoresistance of a series of La1−xSrxMnO3 and La1−x−yCaxSryMnO3 samples, for which structural and ferromagnetic transformation temperatures are in close proximity. On cooling in zero magnetic field, we observe a rapid increase of resistivity just above TC for La1−xSrxMnO3 samples with x < 0.1425 and x ≤ 0.1725 due to the O*-O' and R-O* - structural phase transformations, respectively. This increase is followed by a rapid decrease due to the ferromagnetic transition. The applied magnetic field significantly shifts the ferromagnetic transition to higher temperatures and suppresses the structure-related resistivity increase. We show that a combination of structural and ferromagnetic transitions gives rise to an enhancement of the negative magnetoresistance due to strong spin-lattice coupling. By choosing a proper composition, the enhancement can be optimized to appear in relatively low magnetic fields. A proper selection of Sr and Ca contents in La1−x−yCaxSryMnO3 and preparation conditions leads to an enhancement of the magnetoresistance effect at room temperature.

Artificial superlattice of LaFeO3-LaMnO3 have been formed on SrTiO3(111), (110) and (100) substrates with various stacking periodicity using pulsed laser deposition. Their magnetic properties have been controlled by altering the ordering of magnetic ions (Fe or Mn). Charge disproportionate behaviors are also observed in these superlattices. For the superlattices on (111) plane, all the samples showed ferromagnetic (or ferrimagnetic) behaviors and the same Curie temperature of 230K. In the case of other superlattices formed on (110) and (100), oh the other hand, the increase of the spin frustration effect between LFO-LMO interface with decrease of the stacking periodicity causes reduction of Tc and magnetization. Specially, spin glass like behaviors observed in the superlattices of less than 3/3 stacking periodicity Furthermore, we have constructed heterostructures of Organic/Inorganic multilayers with a sequence of Copper phthalocyanine(CuPc), BaTiO3 and (LaSr)MnO3. In this system, magnetoresistant properties have been controlled by the photo irradiation through the lattice strain and/or induced charges caused by the piezo effect and electric field effect. That is magnetoresistance in the (LaSr)MnO3 layer can be controlled by the shining the light.

Using pulsed laser deposition technique we fabricated films of a continuous series of solid solutions La0.7(Pb1−xSrx)0.3MnO3, which undergo metal-to-insulator phase transition close and above room temperature. The optimal composition for uncooled bolometer applications was found at x = 0.37 with maximum of TCR = 7.4 %K−1@ 295 K. Room temperature bolometer demonstrator has been built and tested. Relatively low excess noise (magnitude γ/n of 3·10−21 cm−3) and high TCR enabled achievement of high signal-to-noise ratio of 8·106 √-Hz/K. The observed frequency dispersion of bolometer response has been ascribed to three relaxation mechanisms of the heat transfer: from film thermistor to substrate, from substrate to thermostat, and heat transfer via leads. For fabricated bolometer heat transfer from substrate to thermostat was found to be the slowest one with a time constant of 0.5 s (correspondent substrate-to-thermostat thermal conductance is G = 3·10−3 W/K). Bolometer performance test yields the responsivity ℜ = 0.6 V/W, detectivity D = 9·106 cm√Hz/W and noise equivalent power NEP of 3·10−8 W/√Hz at 30 Hz frame frequency. Further improvement of bolometer thermal isolation using the micromachining technique is believed to achieve the responsivity about 4·103 V/W and detectivity higher than 109 cm√Hz/W@30 Hz.

We discuss performance of CMR-based bolometers for pulse and modulated electromagnetic radiation detection. Ultimate characteristics of CMR thin film-based bolometers are considered based of current experimental studies of photoresponse.

We grow Pb(Zr,Ti)O3 (001)/La1−xCaxMnO3 (001) hetereostructure epitaxially on Nb doped STO substrate using pulsed laser ablation. A field effect device configuration is formed with the manganite as the channel and the Nb:STO substrate as the gate. Channel resistance modulation by the gate pulsing is studied both with and without magnetic field. We not only find a remarkably large electroresistance effect of 76% at 4× 105V/ cm, but also the complimentarity of this ER effect with the widely studied CMR effect. The large size of this effect and the complimentarity of ER and MR effects strongly suggest a percolative phase separated picture of manganites.

Epitaxial ferroelectric/colossal magnetoresistive PbZr0.52Ti0.48O3/La0.7(Pb,Sr)0.3MnO3 (PZT/LPSMO) thin film heterostructures have been grown onto SrTiO3 single crystals by KrF pulsed laser deposition technique to fabricate nonvolatile magnetosensitive memory. Colossal magnetoresisitivity (CMR) in LPSMO film has been tailored to room temperature by compositional control to get the maximum temperature coefficient of resistivity of 7.3 %K−1 @ 295 K and maximim magnetoresistivity of 27% @ 7 kOe and 300 K. The main processing parameters have been optimized to preserve CMR performance in LPSMO film after deposition of the top ferroelectric layer. Vertical Au/PZT/LPSMO/STO capacitor cell possesses very high dielectric permittivity about 1500 and rather low loss of 5% at 1 kHz, saturation polarization of 40.4 µC/cm2, remnant polarization of 20.6 µC/cm2, coercive field of 22.8 kV/cm, and no visible fatigue after 1.33.108 reversals. Three top contact metals: Au, Pt, and Ta, deposited at room temperature, have been examined. As compared with Ta, Pt and Au top contacts show superior performance regarding to combined properties: high remnant and saturation polarization, low loss and no fatigue while top Ta contacts have been found to be more efficient to reduce leakage in ferroelectric film.

The activity of LaMO3, where M=Cr, Mn, Co, perovskite-type complex oxides in oxygen diffusion and catalytic processes was investigated. For sample preparation freeze-drying technique was used and dynamic thermal isotope exchange method was used to study exchange reaction between 18O from the gas phase and 16O from the samples synthesized, and to investigate the methane catalytic oxidation reaction. The results obtained allowed to indicate temperature intervals of different types of reaction taking place and that LaCrO3 is far less active in mentioned reactions than LaCoO3 and LaMnO3.