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Adding functionalities to existing ferroelectric/ferromagnetic materials showed promising results with exciting physical mechanisms. Pure and bilayer films of strong ferromagnetic oxides, viz, BaFe12O19 (BaM) and La0.67Sr0.33MnO3 (LSMO), were fabricated by pulsed laser deposition. Polycrystalline samples of dense structure, uniform thickness, and monodispersed grain distributions were used to form capacitor-like stack geometry for dielectric and magneto-dielectric (MD) measurements. High dielectric constants at moderately high frequencies with increased relaxation times were observed for the bilayer film and are attributed to the BaM/LSMO strained interface, while Maxwell–Wagner polarization plays an insignificant role. Modeling of dielectric loss tangents and AC conductivity revealed localized carrier hopping between Fe ions in the bilayer film. Pronounced hysteresis loops with a small coercive field and increased saturation magnetization values of BaM/LSMO bilayers, as compared with BaM/Pt, are demonstrated at 300 K; where the role of mixed valence Mn ions in +3 and +4 states at the bottom LSMO electrode is highlighted. MD measurements with varying magnetic fields showed magnetically tunable, large MD coupling values (∼287%) for BaM/LSMO/Pt. The phenomenally high MD values are discussed based on ionic polarization, colossal magnetoresistance of LSMO, and magnetostriction at the BaM/LSMO interface. Our findings propose significant applications of ferromagnetic oxide bilayers in the emerging field of magneto-dielectric coupling devices.

SrTiO3 is a wide bandgap cubic perovskite oxide and displays many exotic properties, i.e., transparent conductivity, photocatalysis, metallicity, ferroelectricity, superconductivity, colossal magnetoresistance, two-dimensional electron gas, etc., due to the manipulations of defect chemistry and constituent elements via impurity doping. This paper reports on the intricacy of the structural and optoelectronic properties of the epitaxially stabilized 5 at. % Ta-doped SrTiO3 (001) thin films on LaAlO3 (001) substrates by systematically varying the growth temperature and oxygen partial pressure during the pulsed laser deposition process. The influences of Ta dopant and growth parameters on the epitaxial quality of these layers are understood by determining the dopant location and its concentration in the SrTiO3 lattice. The complex relationships of optical and electronic properties on growth parameters, dopant concentration, and single crystal quality of the films are demonstrated. The observed low resistivity (∼5 × 10−3 Ω cm) and high optical transparency (∼85%–90%) of optimized Ta-doped SrTiO3 films offer it as an exciting material for next generation transparent optoelectronics.

In this work, we present an investigation of transient magnetic field behavior in thin-walled superconducting tubes. It has been determined that if the thickness of the tube wall is significantly less than Bean’s penetration length, the non-linear magnetic field diffusion equation describing the field propagation process inside the tube can be replaced by a simplified lumped-parameter equation. This makes it possible to quickly calculate the current induced in the tube wall and the magnetic field penetrated in the tube cavity. In order to validate this theory, an experimental study of transient magnetic field penetration into a Pb-doped B-2223 ( Bi 1.8 Pb 0.26 Sr 2 Ca 2 Cu 3 O 10 + x) tube was conducted. This was done at the temperature of liquid nitrogen using a search coil (B-dot) and a miniature colossal magnetoresistance (CMR)-B-scalar magnetic field sensor made from manganite films, which exhibit a CMR phenomenon. The experimental results were then compared with the datasheet of the superconducting tube manufacturer and the 2D axisymmetric finite element model. It was demonstrated that combining the measurements of the magnetic field outside and inside the tube with the lumped-parameter description allows one to obtain the following information: the screened and trapped magnetic field, the critical current density vs the magnetic field dependence, and the power law index of the superconducting tube material. This enables the development of a fast, non-destructive method for testing the quality of superconducting tubular current leads.

We studied the magnetization (M), magnetostriction (λ||), resistivity (ρ), magnetoresistance (MR), and thermoelectric properties of low-doped EuTi1−xNbxO3 (x = 0.003 and 0.005). In both the samples, Eu2+(4f7) spins order antiferromagnetically at T N ≅ 5.5 K, and the paramagnetic to antiferromagnetic transition is accompanied by a spontaneous contraction of the length in the absence of magnetic field and a positive magnetostriction under external magnetic fields. ρ(T) shows non-metallic behavior in the temperature range 400–2.5 K but a weak kink at TN in a zero magnetic field. The application of an external magnetic field induces the semimetal-metal transition and negative MR. The magnitude of negative MR has a maximum value of 82% (57%) under 7 T for x = 0.003 (0.005) at T = 2.5 K, and the MR monotonously decreases with increasing temperature. Thermopower data indicate that the doped carriers are electrons. It is suggested that scattering of 4d1 electrons doped in the impurity band by 4f spin fluctuations is responsible for the colossal magnetoresistance.We studied the magnetization (M), magnetostriction (λ||), resistivity (ρ), magnetoresistance (MR), and thermoelectric properties of low-doped EuTi1−xNbxO3 (x = 0.003 and 0.005). In both the samples, Eu2+(4f7) spins order antiferromagnetically at T N ≅ 5.5 K, and the paramagnetic to antiferromagnetic transition is accompanied by a spontaneous contraction of the length in the absence of magnetic field and a positive magnetostriction under external magnetic fields. ρ(T) shows non-metallic behavior in the temperature range 400–2.5 K but a weak kink at TN in a zero magnetic field. The application of an external magnetic field induces the semimetal-metal transition and negative MR. The magnitude of negative MR has a maximum value of 82% (57%) under 7 T for x = 0.003 (0.005) at T = 2.5 K, and the MR monotonously decreases with increasing temperature. Thermopower data indicate that the doped carriers are electrons. It is suggested that scattering of 4d1 electrons doped in the impurity band by 4f spin fluctua...

Single-phase electron-doped manganite thin films with nominal composition of La0.7Ce0.3MnO3(LCeMO) have been prepared on SrTiO3(100) substrates by pulsed laser deposition. The conditions for obtaining purely single-phase LCeMO films lie within a very narrow window of substrate temperature (Ts∼720°C) and laser energy density (ED∼2J∕cm2) during deposition. In situ postdeposition annealing, mainly to relax the possible epitaxial in-plane tensile strain between the film and the substrate, leads to an increasing c-axis lattice constant accompanied by the formation of secondary CeO2 phase and higher metal-insulator transition temperature. This is indicative of a strong coupling between the electron and lattice degree of freedom.

Polycrystalline La0.7Ca0.3MnO3−δ (LCMO), prepared by a solid-state reaction, was annealed at different temperatures TA. The variation of TA was responsible for observed changes in the physical properties, including a shift in the metal-insulator transition temperature, which is explained by variation in the oxygen content. At low temperatures the magnetization of LCMO samples was also observed to be dependent on TA. A reduction of the grain boundaries leads to enhancement of both the magnetization and the sensitivity for low-field magnetoresistance. By using Mn L3-edge x-ray absorption, it was also found that the Mn3+∕Mn4+ ratio increases with the grain size, and that the oxygen content in LCMO is governed by the grain boundaries.

Al2O3-doped La0.7Sr0.3MnO3(Al2O3-LSMO) thin films were deposited on Si(111) substrate via a pulsed laser deposition. The deposited Al2O3-LSMO composite thin films were characterized by x-ray diffraction, scanning electron microscopy, and electro- and magneto-transport measurements. The main phase in the Al2O3-LSMO composite films was the perovskite phase. Texturelike microstructure was observed in the Al2O3-LSMO composite films while the average grain size remained almost unchanged compared to the pure samples. The metal-insulator transition temperature decreased as a result of the addition of Al2O3 and further reduced with increasing Al2O3 content. A maximum low field mangetoresistance of ∼15% was achieved in the 2∕20Al2O3-LSMO thin films, which could be well explained in terms of the grain boundary tunneling effect. The composition of the composite thin films can be easily tuned by adjusting the target composition. This method is believed to be applicable to exploring the combinations of other manganite...

We fabricated ∼200 nm thin (001)-oriented films of the ferromagnetic metallic perovskite La2/3Ca1/3MnO3 on single crystal (001)-SrTiO3 substrates by dc-sputtering at high oxygen pressure. The samples feature a Curie temperature TC∼260 K and a magnetic moment μ(T→0 K)∼3 μB per Mn atom. The magnetization loops are nearly square-shaped with a coercive field Hc(5 K)=0.03 T that decreases linearly in temperature down to TC. At low temperature, the magnetization shows a decrease ΔM∼T2 and the resistivity an increase Δρ∼T2 as is expected for itinerant electron ferromagnets where single particle excitations dominate. As a further indication of the high quality of the samples, the resistivity without external magnetic field peaks right at TC with a maximum value ρ(H=0,T=TC) of only ∼2 mΩ cm. The magnetoresistance ratio Δρ/ρ0=[ρ(H,T)−ρ(H=0,T)]/ρ(H=0,T) also reaches its maximum value at TC, with Δρ/ρ0(H=6 T,T=TC)∼−50%. The complete absence of this colossal magnetoresistance effect in the low-temperature limit is a f...

Bulk perovskite manganese oxide La1−xSbxMnO3 (x=0.05,0.1) samples were prepared using solid-state reaction technology. Electrical transport and magnetic properties have been investigated. The experimental results show that the compound exhibits typical colossal magnetoresistance (CMR) behavior. The temperature and time dependence of magnetization [M(T) and M(t)] confirm that the compounds are in cluster glass state at temperatures lower than Curie temperature. The zero-field-cooled magnetization strongly depends on the observed time, and all M(t) curves have an inflection point at an observation time very close to wait time tw. All our results show that the La1−xSbxMnO3 (x=0.05, 0.1) compound is a CMR oxide with a MR ratio of about 60% at 225 K and 5 T. X-ray photoelectron spectroscopy analysis has revealed that the Sb cation is in quin-valence state and the new compound could be considered as an electron doped system.

Structural, magnetic and transport studies have been carried out on (La0.7−2xEux)(Ca0.3Srx)MnO3 (0.05⩽x⩽0.25) compounds forming in a distorted orthorhombic structure (space group Pnma, No. 62). The Eu and Sr substitutions avoid any average A-site cation size disparity throughout the series. However, increasing both the cation size mismatch at the A-site and carrier concentration induces interesting changes in structural, transport and magnetic properties. Both insulator–metal transition temperature (Tp) and Curie temperature (TC) decrease with increasing x. The resistivity of all the samples in the semiconducting regime fits to the Variable Range Hopping (VRH) of Mott type model. Carrier localization length, L, obtained from VRH plots, decreases from 4.6 A for x=0.05 to 3.9 A for the x=0.20 sample. In the metallic region, the n term in the resistivity fits to the Zener-Double exchange polynomial law (ρ=ρ0+ρ2T2+ρnTn) increases from n=5.5 for x=0.05 to n=7.5 for x=0.15. From magnetic susceptiblity measureme...

The structure and transport properties of Sm1-xCaxMnO3 with 0.4less than or equal toxless than or equal to0.8 were investigated. With decreasing temperature from 350 K, cooperative Jahn-Teller (JT) distortion develops, leading to the formation of a charge ordered (CO) state and anomalies in the lattice parameters and resistivities. At low temperature the magnetoresistance effect originates from the polarization of the localized t(2g) spins under the magnetic field and decreases with the increase in Ca2+ content x, whereas the stability of the CO state at the CO transition temperature T-CO strongly depends on both Ca2+ content and cooperative JT distortion. These interesting phenomena sufficiently confirm the close relationship among charge, lattice, spin, and orbital degrees of freedom. (C) 2004 American Institute of Physics.

A description of the nonlinear conductivity of mesoscopic systems is formulated and used to describe quantum effects in the giant magnetoresistance of multilayer structures, based on a subdynamics approach. Consideration of the nonlinear response makes it possible to discuss the influence of bias and temperature on giant magnetoresistance. Calculations show that for sandwich structures, the giant magnetoresistance increases when the bias increases, and decreases for negative bias. Compared with the influence of bias, the variation of giant magnetoresistance with temperature is small.

In this study we report the structure, magnetic and electrical transport properties of pervoskite oxide La$sub{0.9}Tesub{0.1}MnOsub{3}$. This is a novel material with the space group R-3c, which shows the spin-glass-like feature at low temperature and has a good colossal magnetoresistance behavior. The magnetoresistance ratio is about 51% at 200 K in a field of 4 T. The XPS measurement suggests that Te ions are in the Te$up{4+}$ state, while Mn ions may be in the 2+ and 3+ valence state.

We have studied the interlayer coupling and the magnetoresistant effect of La0.55Sr0.45MnO3/ La0.67Ca0.33MnO3 structures. Magnetization loops, measured in La0.55Sr0.45MnO3/La0.67Ca0.33MnO3/La0.55Sr0.45MnO3 trilayers, indicate that there is a ferromagnetic coupling of the La0.55Sr0.45MnO3 layers across the La0.67Ca0.33MnO3 spacer up to room temperature, even above the Curie temperature of the La0.67Ca0.33MnO3 layers. However, magnetization versus temperature curves present signatures of the magnetic ordering of both compounds. No extrinsic magnetoresistance associated with the multilayered structure was observed in the whole temperature range due to the presence of the interlayer ferromagnetic coupling.

We have studied the physical properties of epitaxial La0.67−xPrxCa0.33MnO3(LPCMO) (x=0.13, 0.20, 0.27) thin films under different type and degree of substrate induced biaxial strain. Films with thickness of 300, 600, and 1000 A grown on crystalline NdGaO3 (negligible strain), LaAlO3 (compressive strain), and SrTiO3 (tensile strain) by pulsed laser deposition are examined. Our data suggest occurrence of metastable phase mixtures in these films, with the volume fractions controlled by strain. In particular, melting of the charge ordered phase is seen to occur in thin films on SrTiO3 at fields as low as 1 T, in the low temperature regime. The deviation of ρ(T) from the effective medium theory further indicates that LPCMO thin films cannot be described as simple metal–insulator mixtures.

In this letter, the electrical and magnetic properties of La{sub(1-x)}Te{sub(x)}MnO{sub(3)}(x=0.1, 0.15), which is a new material and shows good colossal magnetoresistance (CMR) behavior, have been investigated. These compounds have rhombohedral structure. In this materical, Te replaced a part of La ions, which induced the lattice cell constriction and Mn-O-Mn bond angle widening. X-ray photoemission spectroscopy (XPS) measurement revealed that the Te ions were in the tetravalent state and the manganese ions could be considered as in a mixture state of Mn{sup(2+)} and Mn{Sup(3+)}. Thus the material could be viewed as an electron-doped compound. The Curie temperature (Tc) was about 240 K and 255 K for x=0.1, 0.15, respectively. The maximum magnetoresistance ratio MR=[r(0)-r(H)]/r(0) was about 51% at 200 K and in the applied magnetic field of 40 kOe.

We have prepared trilayer structures that contain a ferromagnetic (La,Ba)MnO3 film sandwiched between two antiferromagnetic LaFeO3 (Neel temperature TN=740 K) or LaCrO3 (TN=280 K) layers. It was found that the magnetoresistance (MR) ratio at 0.8 T was enhanced from 43% in the La0.8Ba0.2MnO3 single layer film to 74% in the La0.8Ba0.2MnO3/LaFeO3 trilayer film. The MR ratio in the La0.8Ba0.2MnO3/LaCrO3 trilayer film, however, was almost identical to that of the single layer film. These results could be interpreted as having resulted from the differences in spin-frustration effects due to the different exchange interactions between the respective neighboring layers.

Thin films of Sr2FeMoO6 have been deposited on single-crystalline and polycrystalline SrTiO3 substrates by pulsed laser deposition from a stoichiometric target. In order to obtain high-quality films, the deposition parameters were systematically optimized. The films grown under optimized conditions show properties comparable to those of bulk Sr2FeMoO6 single crystals. Surprisingly, polycrystalline films obtained by depositing on polycrystalline SrTiO3 substrates do not show any significant low-field magnetoresistance (MR), contrary to expectations for a spin-polarized material. However, after controlled annealing-induced alteration of the grain-boundary properties, a development of the low-field MR feature is clearly observed. The occurrence of the low-field MR is accompanied by nonlinearity in the current-voltage characteristics. These results are analyzed in the light of the prevalent understanding of the properties of this double perovskite material.

Epitaxial thin films of La0.67Ca0.33MnO3 were implanted with 30 and 100 keV 57Fe ions at different fluence values to achieve a uniform implant distribution. The resistivity of the film increases as fluence increases, but the peak resistivity temperature Tp does not change significantly for the as-implanted sample. Annealing of the implanted samples at 950 °C allows recovery of the structural properties of the films and leads to interesting properties: increase of the peak resistivity and of the colossal magnetoresistance values, and decrease of Tp. The decrease in Tp is of ∼130 K, and the increase in resistivity is almost a factor of 28 as compared to the as-implanted sample.

Polycrystalline samples (La1−xGdx)0.7 Ca0.3 MnO3 with x=0, 0.05, 0.2, 0.3, and 0.4 were synthesized by a solid-phase reaction method and we measured their ac magnetic susceptibility, resistivity, linear thermal expansion coefficient, magnetization, and magnetostriction as a function of temperature by using strain gauge, ac susceptometer, and a vibrating sample magnetometer. An extra contribution to the expansion coefficient was observed at Tc as a consequence of the polaron effect as well as the paramagnetic–ferromagnetic and metal–insulator transition. Electrical, magnetic, and lattice structural transition temperatures correspond to 253±5 K and 224±5 with respect to x=0 and 0.05, respectively. These results prove the presence of strong electron–phonon and spin coupling. Under the external magnetic field, transition temperatures shift to higher ones and the peak on the temperature dependence of the expansion coefficient is suppressed. These phenomena could be related to colossal magnetoresistance.

We show that it is possible, by anelastic spectroscopy measurements, to identify beyond the intrinsic limits of other techniques such as diffraction, resistivity, or extended x-ray absorption fine structure, the nature of spurious and minority phases possibly present in the experimental samples. We will stress how the high selectivity of this spectroscopy can be useful in studying classes of materials such as colossal magnetoresistance manganites or other transition metal oxides where the characterization of the specimens assumes a crucial role.

The layered manganite La1.4Sr1.6−yBayMn2O7 was prepared to investigate the relation between magnetotransport properties and lattice expansion in manganites with Sr3Ti2O7-type structure. The lattice expansion caused by Ba2+ substitution enhances the ferromagnetic coupling within the perovskite MnO2 bilayers. Lightly Ba2+ doped samples display the colossal magnetoresistance effect common in the mixed-valent manganese oxides. In the heavily Ba2+ doped samples, the three-dimensional ferromagnetic transition disappears, whereas the metal–insulator transition and the marked magnetoresistance effect remain. By increasing Ba+ content, the metal–insulator transition unexpectedly shifts to a higher temperature. This abnormal behavior may be due to the correlation between spin clusters and percolative transport process in these materials.

The oxygen content of La0.5Ca0.5MnOy was tuned by annealing the samples at high temperatures in flowing nitrogen with graphite powder nearby. The reduction of oxygen content has dramatic effect on the electrical transport and magnetic properties. The samples with y=2.983, 2.83, and 2.803 show an insulator-metal transition, and an unusual temperature and magnetic-field dependence of the magnetoresistance. The paramagnetic-ferromagnetic transition also shifts to lower temperatures and the antiferromagnetic transition at lower temperature is suppressed. The results are discussed in terms of the effect of oxygen vacancies on the various properties of La0.5Ca0.5MnOy. (C) 2002 American Institute of Physics.

The temperature dependence of magnetoresistance in insulating granular systems is studied. At low temperatures the magnetoresistance is enhanced drastically as a result of high-order tunneling. On the other hand, decay of spin polarization will lead to a decrease of magnetoresistance at high temperatures. The role of grain size distribution is investigated and the intergrain correlation is found very crucial in determining the magnitude of magnetoresistance. Our calculations agree with the experimental data well.

La0.67Ca0.33Mn1−xCuxO3 (x=0 and 0.15) epitaxial thin films were grown on the (100) LaAlO3 substrates, and the temperature dependence of their resistivity was measured in magnetic fields up to 12 T by a four-probe technique. We found that the competition between the ferromagnetic metallic (FM) and paramagnetic insulating (PI) phases plays an important role in the observed colossal magnetoresistance (CMR) effect. Based on a scenario that the doped manganites approximately consist of phase-separated FM and PI regions, a simple phenomenological model was proposed to describe the CMR effect. Using this model, we calculated the resistivity as functions of temperature and magnetic field. The model not only qualitatively accounts for some main features related to the CMR effect, but also quantitatively agrees with the experimental observations.

We report the temperature and magnetic field dependence of the resistivity of La2/3Sr1/3MnO3 thin film over a wide temperature range and in high magnetic fields up to 20 T. Both above and below the ferromagnetic (FM) transition, the field dependence of the magnetoresistance (MR) can be described well using the extended Mott hopping conduction model. The large MR is proportional to the Brillouin function BJ in the FM phase and to BJ2 in the paramagnetic state which is consistent with this model. The value of spin moment J deduced from the temperature and magnetic field dependence of the MR is large (∼60) in the vicinity of the FM transition. This large value of J has been attributed to the presence of magnetic clusters due to the short-range FM ordering.

The magnetization and magnetoresistance of Au80Fe20 and Au70Fe30 melt-spun ribbons have been measured between 2 and 300 K. The solid solution Au80Fe20, paramagnetic at room temperature, exhibits a transition to a frustrated ferromagnetic state on lowering T. The solid solution Au70Fe30 is in a similar ordered state over the entire temperature interval. A negative magnetoresistance is observed in both systems. In Au80Fe20, its functional dependence on magnetization gradually changes from parabolic (typical of the paramagnetic phase) to box-like with lowering T. In Au70Fe30, the shape of the curves is always box-like. In both alloys, this effect exhibits a nonmonotonic behavior with temperature. The magnetoresistance of these alloys arises from the spin-dependent scattering of conduction electrons at the interfaces between adjacent regions of magnetic coherence of size comparable to the electron mean free path. This effect is therefore referred to as the “proximity” magnetoresistance. Two magnetization mech...

The electrical, magnetic, and transport properties of Cu-doped polycrystalline samples Sr2Fe1−xCuxMoO6 with ordered double perovskite structure have been investigated systematically. Analysis of the x-ray powder diffraction pattern based on the Rietveld analysis indicates that the substitution of Fe3+ ions by Cu2+ ions enhances the site location order of Fe, Cu, and Mo on the B site for the high-doping-level samples (x=0.20, 0.25, 0.30). With increasing doping level, a transition from semiconductor to metal behavior was also found to occur. Furthermore, the transition temperature was found to decrease either by the application of a magnetic field or by increasing the doping level. It can be concluded that the existence of Cu2+ ions induces the occurrence of Fe3+δ ions and the double exchange interaction in Fe3+–O–Mo–O–Fe3+δ. The transport mechanism in these samples can be attributed to the competition between the metal phase and the semiconductor phase arising from the doping of Cu2+ ions. Both the semico...

Substitutions at the Mn site by cations M with oxidation states higher than 4+, such as Mo6+ and Ru5+, are shown to stabilize SrMn1−xMxO3 cubic perovskite manganites. This effect is explained by the induced Mn valency shift, which corresponds to electron doping by Mn3+ in the Mn4+ matrix. Interestingly, these electron-doped manganites, characterized by large A-site cationic size, exhibit coupled structural, magnetic, and transport transitions close to or beyond 300 K for M=Ru5+ and M=Mo6+, respectively. These transitions are characteristic of the dz2 orbital ordering generally associated with C-type antiferromagnetism. This result contrasts with the inhomogeneous ferromagnetic metallic state induced by Ru in CaMnO3. The possibility to induce orbital/charge ordering in CaMn1−xMoxO3 or orbital ordering in SrMn1−xMxO3 (M=Ru, Mo) with M contents superior to 10% makes it more difficult to explain based on long-range cooperative Jahn–Teller phenomena in mixed-valency manganites.

Transport, magnetic, magneto-optical (Kerr effect) and optical (light absorption) properties have been studied in an oriented polycrystalline La0.67Ca0.33MnO3 film which shows colossal magnetoresistance. The correlations between these properties are presented. A giant change in infrared light transmission (more than a thousand-fold decrease) is observed on crossing the Curie temperature (about 270 K) from high to low temperature. Large changes in transmittance in a magnetic field were observed as well. The giant changes in transmittance and the large magnetotransmittance can be used for development of IR optoelectronic devices controlled by thermal and magnetic fields. Required material characteristics of doped manganites for these devices are discussed.

Penetration of the electromagnetic field through plate-shaped bulk polycrystalline sintered Pb and Y–Ba doped manganite samples is studied in the frequency range from 20 kHz to 30 MHz. Strong magnetic-field dependence of the transmission coefficient is observed. The penetration data are compared with the other magnetic-field dependent parameters: the magnetic permeability, magnetoresistance, and magnetoimpedance. Unusual frequency dependence of the penetration depth is observed.

We report an experimental observation of strikingly contrasting hysteresis behaviors between the longitudinal magneto-optical Kerr rotation, θK, and ellipticity, eK, in NiFe/FeMn/Co films. For example, one is likely to reproduce a typical magnetic hysteresis loop obtainable with vibrating sample magnetometry while the other one does reproduce magnetoresistance (MR)-like curves in some cases. Interestingly, θK/eK loops form inverse MR curves. The contrasting hysteresis behavior could be explained by the discriminate sensitivity of θK and eK to the ferromagnetic NiFe as well as Co layers. Using a simple model, we determine the sensitivity ratios of the Co to NiFe layer for both signals, which are far from unity as much as θKCo/θKNiFe=−1.4 and eKCo/eKNiFe=8.5. These values may allow one to understand the anomaly of the remarkably contrasting loops observed in NiFe/FeMn/Co trilayer films.

The discovery of the colossal magnetoresistance and pressure effects introduced new questions concerning the complex interplay among lattice structure, magnetism, and transport in doped perovskite manganites. To observe the interplay between the effect of pressure and strain due to the substrate in the La2/3Ca1/3MnO3 compound, we produced epitaxial films with the thickness varied between 20 and 100 nm on SrTiO3 substrates, using the pulse laser deposition technique and under the same epitaxial growth conditions. We measured magnetic transition temperature TC and resistivity ρ, as a function of pressure up to 8 kbar. Using these results, the dependence of bond compression on pressure, and the lattice distortion induced by the substrate, are discussed. We also report a universal behavior from the plot of d ln TC/dP and dρ/dP versus TC for these films, as well as previously published results on ceramic and thin films of this compound.