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Abstract Polycrystalline perovskite-type manganite La 0.65 Ca 0.35 Mn 1-x Ni x O 3 were prepared by sol-gel method. X-ray diffraction measurement showed that all samples have a single phase. Rietveld's refinement result of X-ray diffraction indicates that our samples have an orthorhombic structure with pnma space group. Magnetization measurements versus temperature in a magnetic applied field of 0.1 T showed that Ni-doping leads to a paramagnetic to ferromagnetic transition with a Curie temperature decreasing from 272 K to 194 K. When x = 0.05, the Tc of the sample was adjusted to near room temperature. The maximum magnetic entropy change - ΔS M corresponding to a 3 T magnetic field variation was found to be 4.76 J/kg K and about 69.59 J/kg of relative cooling power for La 0.65 Ca 0.35 Mn 0.95 Ni 0.05 O 3. Besides, Arrott plots showed that our sample exhibit a second-order on the phase transition of the manganite. Highlights • The traditional sol-gel method was improved by using citric acid as complexant, shortening the preparation period and reducing the sintering temperature. • Doping at the Mn site severely affects the Curie temperature of the sample. Our results show the sample La 0.65 Ca 0.35 Mn 0.95 Ni 0.05 O 3 exhibited a magnetic entropy change -ΔS M 4.76 J/kg K and a RCP 69.59 J/kg under a 3.0 T magnetic field near Tc. • In theory, the parameters such as magnetic entropy change and relative refrigeration capacity of the prepared products are simulated, and the experimental results are compared with the theoretical predictions. • The sample we obtained can be used as candidates for potential applications for magnetic refrigeration. [ABSTRACT FROM AUTHOR]

Abstract: The dependence of the transformation coefficient of the four-pole network with the toroid core made of the La0.6Pb0.4MnO3 manganite on dc biasing magnetic field and frequency was experimentally investigated. The factors which influence the value of the transmission coefficient are analyzed. In the megahertz frequency range the frequency dependence of the transformation coefficient has a resonant form with the position of the maximum and amplitude increasing with the dc biasing. The dc magnetic field dependence of the phase shift between the voltages in the primary and secondary windings was investigated. The results are interpreted taking into account the imaginary component of magnetic permeability of the core material. [Copyright &y& Elsevier]

Abstract: With a view to understand the magnetic and electrical behavior of monovalent substituted lanthanum manganites, a series of materials were prepared by sol–gel route by sintering at 1200°C. The X-ray diffraction data were analyzed using Rietveld refinement technique and it has been found that all the samples were found to crystallize into rhombohedral structure with R3¯c space group. The values of ferro to paramagnetic (T C) and metal–insulator transition (T P) temperatures were obtained using ac susceptibility and electrical resistivity data, respectively. It has been found that sodium-, potassium- and rubidium-doped samples exhibit two peaks in the electrical resistivity vs. temperature plots. The observed behavior has been explained on the basis of oxygen deficiency present in the samples. The electrical resistivity data were analyzed using various theoretical models and it has been concluded that the electrical resistivity data in the low-temperature regime (TT P) were explained using variable range and small polaron hopping mechanisms. [Copyright &y& Elsevier]

Abstract: The perovskite p–n heterojunctions were fabricated by depositing La0.9Sr0.1MnO3 (LSMO) layers with thicknesses ranging from 20 to 400Å on SrNb0.01Ti0.99O3 (SNTO) single-crystal substrates by laser molecular beam epitaxy (laser-MBE). The open-circuit photovoltage of the LSMO/SNTO heterojunction at room temperature increases with the increase of the thickness of LSMO layer. This result is ascribed to the increase of the carrier amount and the enhancement of the built-in electric field in the space-charge region of the LSMO/SNTO heterojunction with the increase of the thickness of LSMO layer. Furthermore, we found that the speed of photovoltaic response is almost independent of the thickness of LSMO layer in the heterojunction. [Copyright &y& Elsevier]

Abstract: ESR spectra were measured in the series Y1− x Ca x MnO3 (YCa) (0⩽x⩽1) obtaining the dependences with x and T. Anomalies detected in the ESR parameters (resonance field, line width and line intensity) allowed us to determine magnetic and structural transitions. We have constructed a phase diagram T vs. x in order to contrast ESR results with those obtained by susceptibility and X-ray diffraction. [Copyright &y& Elsevier]

Abstract: We study the competing phases at the crossover from localized to itinerant electronic behavior in the system Pr0.5(Ca1− x Sr x )0.5MnO3, with 0.10⩽x⩽0.75. The study was performed by Q-band (35GHz) electron spin resonance (ESR) spectroscopy. At room temperature, the samples show a single Lorentzian line centered at g=2.020 (5). Instead, at low temperature all the samples present a ferromagnetic resonance line (FMR) that coexists with a paramagnetic (PM) absorption. For x=0.15, the FMR absorption is observed at T C=200K. This transition shifts to higher temperatures when x increases and for x=0.75, T C=260K. The ferromagnetic metallic (FM) phase changes from a minority phase, when x<0.2, to a majority one, for x>0.2. We fit the temperature dependence of the ESR spectra considering an FM phase with uniaxial anisotropy that coexists with a PM phase. We have found that the anisotropy field of the FM phase increases with x. [Copyright &y& Elsevier]

Abstract: The temperature dependencies of the specific heat, thermal diffusivity and thermal conductivity in polycrystalline and manganites are measured in wide temperature range of 77–300K. These characteristics reveal peculiarities at magnetic phase transition and transition into charge-ordered (CO) state. It is shown that a change of the phonon spectrum due to lattice contraction is the main reason of a sharp decrease of the thermal conductivity in at the transition to the antiferromagnetic CO state. Using the experimental thermal diffusivity data and sound velocity data a temperature dependency of the phonon mean free path is calculated. [Copyright &y& Elsevier]

Abstract: Bulk polycrystalline layered perovskite sample La2Sm0.4Sr0.6Mn2O7 was prepared by the conventional solid-state reaction technique. Temperature dependence of magnetization measurements in the zero-field-cooled and field-cooled conditions with an applied magnetic field of 100Oe indicates that layered manganite La2Sm0.4Sr0.6Mn2O7 undergoes a paramagnetic to ferromagnetic transition at Curie temperature T c∼355K. The magnetic transition temperature (T c) is much higher than metal–insulator transition temperature (T p) obtained from temperature dependence resistivity measurement. The anisotropic exchange interaction may be one of the reasons resulting in a large deviation between T c and T p. Field dependence of magnetization measurements showed a high value of magnetization (62emu/g at 5K and 42emu/g at 300K) in an applied magnetic field of 1T. At 78K, a sharp increase of magnetoresistance was observed at low magnetic fields followed by a weak and linear dependence at high fields. [Copyright &y& Elsevier]

Abstract: X-ray diffraction and magnetization measurements have been carried out in manganites (, Ga, Fe, Mn, and In). It was found that the samples belong to orthorhombic phase and lattice parameters increase with increasing ionic radius of the dopants. Curie temperature, , changes with doping due to a difference between the electron configuration (E-factor) and ionic radius (S-factor) of the dopants and manganese trivalent ion. The E-factor affects the stronger than the S-factor and causes the decrease. The S-factor can cause both positive and negative change in . The change, caused by the S-factor, is positive if ionic radius of the dopant is less than that of ion, and negative in opposite case, if dopant ionic radius is larger than that of ion. Saturation magnetization of the manganites decreases continuously with increasing ionic radius of the substituents and almost independent of magnetic nature of the dopants. [Copyright &y& Elsevier]

Abstract: Polycrystalline La0.85Na0.15Mn1− x Ni x O3 (, 0.05, 0.1) thin films were successfully fabricated on Si (100) substrates using chemical solution deposition method. The results revealed that with the increase of the Ni content, the X-ray diffraction intensity ratio of I (111)/I (200) increased, whereas both the grain size and the roughness decreased. The magnetic and transport measurements showed that it was effective to tune the magnetoresistance (MR) effects via Ni doping at Mn sites. [Copyright &y& Elsevier]

Abstract: We have performed transverse field measurements of the non-oxide perovskite compound down to 20mK to determine the magnetic field penetration depth, finding . We have also performed zero-field measurements and can exclude any spontaneous internal fields greater than 0.02G. Thus, we conclude that the superconducting state does not possess broken time reversal symmetry. [Copyright &y& Elsevier]

Abstract: We present magnetization and muon spin resonance data on the single layered manganite LaSrMnO4, nominally containing no holes. Magnetization data corroborate antiferromagnetic (AF) spin order but it also suggest additional static moments with a magnetic anisotropy parallel to the AF easy axis, at low temperatures. Our data confirm the existence of these statics moments and imply that they are in a metastable, frozen state. Upon heating, the metastability disappears and for the additional moments a very slow dynamic is detected. [Copyright &y& Elsevier]

Abstract: We present a comparative investigation of the Bi manganites with commensurate composition : Bi0.75Sr0.25MnO3 and Bi0.75Ca0.25MnO3. μSR and diffraction data confirm different structural, magnetic and electronic transitions in the two compounds. The robust charge-order phase detected with Sr do not occur in Bi0.75Ca0.25MnO3, which present inhomogeneous magnetism and short-range charge order. In both compounds the application of magnetic fields produces a continuous progressive canting of the moments, visible even for relatively small fields . [Copyright &y& Elsevier]

Abstract: Temperature-dependent zero-, longitudinal- and transverse-field spectra have been recorded in nanometric obtained by mechanical alloying. The alloy comprises Fe(Cu) nanoparticles (5nm) in a Ag matrix formed by 16nm particles, as deduced from the Rietveld refinement of the X-ray diffraction pattern. The muon depolarization can be described by a Dynamical Lorentzian Kubo–Toyabe function. This is in agreement with a high degree of interparticle dipolar interactions, giving rise to a cluster spin glass-like behavior below 100K. The intra particle interactions are also probed by the , and influence the thermal variation of the static width. [Copyright &y& Elsevier]

Abstract: We have performed muon spin relaxation () experiments on undoped CaMnO3 and electron-doped for and 0.3. Undoped CaMnO3 is a G-type antiferromagnet with a Néel temperature of . The signal shows three well-defined frequencies, which decrease continuously with temperature and becomes zero at . The electron-doped Ca0.85Sm0.15MnO3 which shows colossal magnetoresistive (CMR) behaviour, undergoes a structural and magnetic transition at . The signal shows heavily damped oscillating signal. The frequency decreases continuously with increasing temperature. Ca0.9Sm0.1MnO3 and Ca0.7 Sm0.3MnO3 show only relaxation and do not show any frequency. We have determined temperature variation of the muon relaxation rates below and above the magnetic and charge order transitions under zero and longitudinal magnetic fields, which give important information about the nature of these transitions. [Copyright &y& Elsevier]

Abstract: Zero-field SR experiments were performed on a series of polycrystalline samples of double perovskites , ; , ) synthesized under high pressure. Spontaneous precession frequencies, of comparable magnitude to those previously reported in , were observed in all the family members except . For all the samples, SR yielded determinations of the magnetic transition temperatures and of the order parameter in agreement with other techniques, but also revealed a peculiar phase separation in , absent in the other compounds. [Copyright &y& Elsevier]

Abstract: A study on the effect of Fe doping on the magnetic properties of , and perovskites is conducted using muon spectroscopy and macroscopic static magnetization measurements. For , magnetization curves show a clear ferromagnetic component while a 20% Fe doping leads to the appearance of a kink in zero-field curves at low temperatures, attributed to progressive spin freezing together with a reduction of the ferromagnetic component. On dynamic grounds, we show that this effect translates into the appearance of non-exponential relaxation as is crossed from above. [Copyright &y& Elsevier]

Abstract: We report -NMR measurements of the nuclear spin relaxation rate in a thin film of La0.67Ca0.33MnO3 (LCMO) using a low-energy beam of spin-polarized 8Li. In a small magnetic field of 150G, there is a broad peak in near the Curie temperature and a dramatic decrease in at lower temperatures. This is attributed to a critical slowing down of the spin fluctuations near and freezing of the magnetic excitations at low temperatures, respectively. In addition, there is a small amplitude, slow relaxing component at high temperatures, which we attribute to 8Li in the SrTiO3 substrate. There is an indication that the spin relaxation rate in the substrate is also peaked at due to close proximity to the magnetic film. These results establish that low-energy -NMR can be used as a probe of magnetic fluctuations in magnetic thin films over a wide range of temperatures. [Copyright &y& Elsevier]

Abstract: The properties of electrical and magnetic transport in bilayer perovskite manganite LaCa2Mn2O7, were investigated by the measurements of resistivity and magnetization. A distinct increasing in resistivity at low temperatures, which is in good agreement with an obvious decreasing in magnetization at the corresponding temperature region was observed. It was suggested that the sample undergoes a transition from ferromagnetic metallic to charge localization state caused by the antiferromagnetic charge ordering (CO). The behavior of photoinduced charge delocalization was observed under irradiation of He–Ne laser (632.8nm) at the low temperatures. It can be explained in terms of the effect of photoinduced charge transfer from O-2p to Mn4+-3d eg orbital state resulting in the partial melting of CO state. [Copyright &y& Elsevier]

Abstract: We present a study of charge ordering and electronic phase separation (EPS) phenomenon in Bi x Sr1− x MnO3, for an exhaustive range of x (0.25⩽x⩽0.75), by STM/STS at room temperature (RT) and specific heat measurements at high temperatures (350–650K). Atomically resolved STM images of the samples, in real space, show the presence of stripe-like charge-ordered (CO) phase coexisting with charge-disordered (CD) phase. The STM images further reveal that the fraction of CO phase increases with an increase in x. The conductance spectra of these phases measured at nano level by STS are discussed. The transition to CO phase above RT is corroborated by specific heat measurements in all samples, giving a T CO(x) phase diagram for this system. [Copyright &y& Elsevier]

Abstract: Perovskite La2/3Ca1/3MnO3 (LCMO)/La2/3Sr1/3CoO3 (LSCO) and LSCO/LCMO bilayer films have been fabricated on single-crystal NdGaO3 substrates (110), and their transport and magnetic properties have been investigated. The magnetoresistance of the bilayer LSCO/LCMO is about 1.7% under the field of 10kOe at 230K, whereas that of the bilayer LCMO/LSCO is larger and is ∼10%. A waist-like hysteresis loop occurs in LSCO/LCMO, while a single-step one in LCMO/LSCO. The behavior is explained by some magnetic coupling. [Copyright &y& Elsevier]

Abstract: A study of crystal structure and magnetization of La0.7Ca0.3− x Sr x MnO3 lanthanum manganites (0.105⩽x⩽0.18) is presented. At room temperature thex=0.105, 0.12 and 0.135 samples were orthorhombic Pbnm phase, andx=0.15, 0.165 and 0.18 compositions were rhombohedralR 3¯ c phase. The magnetization on temperature dependence,M=M(T), for the samples (exceptx=0.135) showed usual (without any “kink”) behaviour. TheM=M(T) curve for thex=0.135 sample revealed two-step dependence with the inflexion points at 309 and 320K. The effect is explained by a supposition that the temperatures are the Curie points of Pbnm andR 3¯ c phases, respectively, and caused by the structural orthorhombic–rhombohedral phase transition observed in the sample at the above temperature interval. [Copyright &y& Elsevier]

Abstract: Systematic studies of X-ray, resistivity (), Hall effect, thermal conductivity (), and thermopower () have been performed on polycrystalline Sr0.9Ce0.1MnO3 sample. While cooling, it undergoes a first-order metal–insulator transition at around 318K, which is associated with a structural transition due to Jahn-Teller ordering. Both Hall coefficient () and thermopower () show negative values, indicating that the carriers in the sample are electrons. In the whole measuring temperature range, , with rather low thermal conductivity value, is related to unusually large static and dynamic lattice distortions of the octahedra. Below 200K, both and follow the variable range hopping (VRH) model. In contrast, in the temperature range of 200–320K, a small polaron behavior can be invoked by the electron–phonon interaction. [Copyright &y& Elsevier]

Abstract: The temperature dependence of the electrical resistivity in monovalent (Ag) substituted LaMnO3 has been investigated between 10 and 350K for both and 0.8T. The polycrystalline pellets of the composition La1− x Ag x MnO3 (0&#60;x&#60;0.3) were prepared by a novel pyrophoric method. Above the metal–insulator transition temperature, the resistivity is well represented by adiabatic polaronic model, while below the peak up to about 100K, the resistivity is governed by an equation of the type, (2&#60;p&#60;2.5). All the samples clearly reveal the existence of zero field resistivity minimum, which is influenced by applied magnetic field (H=0.8T). The depth the resistivity minimum decreases considerably in presence of the applied magnetic field. Analysis of our results in terms of the model based on charge carrier tunneling between the antiferro magnetically coupled grains shows excellent agreement with the experimental data for both and 0.8T. [Copyright &y& Elsevier]

Abstract: Temperature dependences of resistivity and magnetization of electron-doped R0.16Ca0.84MnO3 (R=Pr, Gd, Eu) orthomanganites have been studied under applied pressures up to 11kbar. For Pr0.16Ca0.84MnO3, the transition temperature between antiferromagnetic insulating and paramagnetic semi-metallic state decreases under pressure at the rate . The sign of the effect is opposite and the value is an order of magnitude lower than that for ferromagnetic metallic hole-doped R1− x D x MnO3 (, D=Ca, Sr, —percolation threshold) compounds. The negative sign of the effect is in evident contradiction with a positive shift of the magnetic transition temperature of the parent compound CaMnO3. To interpret this result, a possibility of electron delocalization and a crossover to a band antiferromagnetism by electron doping have been suggested. The compounds Eu0.16Ca0.84MnO3 and Gd0.16Ca0.84MnO3 below t are in a mixed magnetic state with coexisting ferro- and antiferromagnetic exchange interactions. The weak pressure effect on for Eu0.16Ca0.84MnO3 does not correlate with the record of the magnetoresistance effect of electron-doped compounds. Considering the obtained applied pressure data, the role of interatomic distances in the formation of CMR effect for electron-doped orthomanganites is discussed. [Copyright &y& Elsevier]

Abstract: Bi-doped lanthanum manganite with chemical composition of La0.62Bi0.05Ca0.33MnO3 has been prepared by the standard solid-state process. The effect of Bi doping on the sintering temperature, the magnetic and magnetocaloric properties has been investigated. Bi2O3 was found to be an effective sintering aid for La0.67Ca0.33MnO3 . It was found that small amounts of Bi doping () can lower the sintering temperature about 200°C. Bi-doped samples also exhibited a large magnetic entropy change, |ΔS m|=3.5J/kgK under 1T field at the Curie temperature. [Copyright &y& Elsevier]

Abstract: The crystallographic structure of La0.7Ca0.3MnO3 (LCMO) ultra-thin films grown on SrTiO3(001) has been investigated by surface X-ray diffraction (SXD) and the correlation between their transport and magnetic properties and crystallographic structure is discussed. LCMO thin films in a thickness range between 2.4 and 27nm were grown by DC-sputtering on SrTiO3(001). We distinguish two different crystallographic structures associated to the 2.4 and 27nm thin films, respectively. The 27nm film structure corresponds to a tetragonal perovskite (space group Pbnm), as has been reported for bulk LCMO. For the 2.4nm film the La/Ca ions are located at the regular position of an ideal perovskite and the MnO6 octahedrons are aligned along the c-axis. The MnO2 stacking layer (basal plane) is distorted and coplanar to the a–b crystallographic axis with an anti-correlation between octahedron layers. This observed distortion is not compatible with the Pbnm space group. The new phase, which cannot be excluded to coexist at the interface of thicker films, can be described, as an example, through an I4/mcm or Pbcn space group. Based on the observed structure, plausible models to explain their transport and magnetic behaviour are proposed. For the 2.4nm film, an octahedron in-plane (basal plane) distortion induced by the substrate is observed. Thicker films behave structurally and magnetically as bulk-like materials. [Copyright &y& Elsevier]

Abstract: X-ray diffraction (XRD) and electron paramagnetic resonance (EPR) have been carried out in a La-deficient sample of La0.54Ca0.32MnO3. From the XRD pattern it was found that the crystal structure has been distorted by the deficiency in A (=La, Ca) position. The temperature dependence of EPR line intensity was successfully fitted by the exponential law based on the small polaron hopping model. High values of an activation energy () derived from EPR data are believed to relate to the above distortion, but EPR line-width, ΔHpp, and a slope, b, of the ΔHpp temperature dependence are not. [Copyright &y& Elsevier]

Abstract: The magnetic, transport and magnetoresistive properties of () crystals prepared by the floating-zone method are studied. In general, these properties testify to rather good crystal perfection of the sample studied. In particular, a huge magnetoresistance ( in the field is about ) is found near the Curie temperature (216K). At the same time, some distinct features of measured properties indicate the influence of extrinsic inhomogeneities arising due to technological factors in the sample preparation. Analysis of the data obtained shows that these are rare grain boundaries and twins. [Copyright &y& Elsevier]

Abstract: The pressure derivative of the order–order transition T1 and the order–disorder transition at small Tc is calculated using a magnetostriction and polaron extended deGennes model in the low x-doped region. According to this model, in the case where there is a semiconducting gap there is no direct pressure dependence of the transition lines but only an indirect one which is connected with the pressure dependence of the transfer integral, even if we have polaronic states. In the case where T1 and the metal–insulator transition Tmi split, there is a direct (quadratic) dependence which is based on a static (polaron) susceptibility of the insulating band edge electronic–phononic states. Pressure experiments on manganite compounds are shown which are consistent with the predictions of the model in detail, e.g. a correlation between dTmi/dp shifts and resistivity changes. [Copyright &y& Elsevier]

Abstract: Structural and magnetic properties of manganite-based multilayers, La2/3Sr1/3MnO3/CaMnO3, composed of ferromagnetic metals and antiferromagnetic insulator barriers are investigated in this work. Compounds of similar lattice parameters were used to build the samples, so we expect an excellent stacking of the different layers along the structure. To get a first insight of this system, the crystalline structure of a series of samples, grown on (100) SrTiO3 and (100) MgO single-crystalline substrates, has been studied. X-ray diffraction patterns show that the structure is strongly textured in the (100) direction when grown on SrTiO3, regardless the composition of the bottom layer. A different result is found on the same system grown on MgO: when the buffer layer is CaMnO3, the structure grows in the (110) orientation while it grows in the (100) direction when the bottom layer is La2/3Sr1/3MnO3. Magnetic coupling of the ferromagnetic layers across the antiferromagnetic spacer has been studied with magnetization measurements. [Copyright &y& Elsevier]

Abstract: Here we address many of the fundamental open questions regarding the glassy behavior of the magnetic/electronic phase segregated state in rare earth perovskites. Magnetic relaxation (AC/DC) support a scenario in which collective effects (memory, ageing, etc.) can be understood as due to intercluster interactions. We propose that the phase segregated state (PSS) constitutes a sort of self-generated assembly of magnetic clusters in which the magnetic interaction introduces collectivity among them. The strength of the interactions can be tuned by composition and/or magnetic field, through the control of the size and concentration of the magnetic clusters. These results are general, applicable to other systems close to a localized to itinerant transition, like cobaltates, cuprates, etc. [Copyright &y& Elsevier]

Abstract: We have investigated the structural, magnetic, electrical transport and electron spin resonance properties of polycrystalline prepared by a sol–gel process. Above 270K, the compound is a paramagnetic insulator. As the compound is cooled from room temperature, ferromagnetic clusters are firstly developed below 270K. Nonetheless, the paramagnetic components still coexist with the ferromagnetic clusters. For , a CE-type antiferromagnetic phase appears which makes the magnetization to decrease with decreasing temperature. The compound still reveals metallic characteristics below 160K due to a lot of ferromagnetic clusters coexisting with the antiferromagnetic domains. [Copyright &y& Elsevier]

We present a comparative investigation under field of three Bi1−xSrxMnO3 manganites in the low-doping regime (x&les;0.50). Powdered samples were investigated in pulsed fields up to 35, 50 or 130 T depending on the compound (x=0.25, 0.33, 0.50). Remarkable differences are found in the M(H) curves when comparing the response to the magnetic field of the two different charge-order phases. [Copyright &y& Elsevier]

Magnetisation and susceptibility measurements have been performed on the oxygen isotope-substituted manganite Pr0.7Ca0.3Mn16–18O3 in pulse magnetic fields up to 35 T in the temperature range 78–300 K. It was found that the charge-ordering transition temperature TCO&ap;210 K and temperature of antiferromagnetic ordering TAFM&ap;125 K in this narrow band manganite are independent on isotope content. The magnetic-field-induced transition into ferromagnetic state was observed in both isotope-substituted samples at temperatures TFM. Isotope substitution has been proved to have a significant impact on the critical field HC of this transition. We found that magnetisation curves are qualitatively different for both isotopic samples. The sample with natural oxygen has the positive derivative dHC/dT on the whole T–H plane. In compound with 18O, HC is shifted to the higher fields (HC∼20 T), being nearly temperature-independent at T>120 K. As the temperature decreases (T), this transition disappears and a more complicated behaviour arises at magnetic fields 6–14 T. [Copyright &y& Elsevier]

Abstract: We have studied an internal friction (IF) peak at 400K which appears when site A in manganite type ABO3 is partially substituted by Ca, Sr and Ba atoms. In the case of total substitution in CaMnO3, the 400K peak is absent. The appearance and the increase of this peak measured in La1− x Ca x MnO3 manganites with x= 0, 0.1, 0.2 and 0.33, reported in Salva et al. Physica B 384 (2006) 62], was associated to a Zener relaxation of the cations occupying equivalent crystallographic sites. In La2/3Sr1/3MnO3 and La2/3Ba1/3MnO3 compounds, the 400K peak is also observed [S.S. Seiro, A.A. Ghilarducci, H.R. Salva, M. Vasquez Mansilla, M. Saint-Paul, P. Lejay, P. Monceau, J. Magn. Magn. Mater. 226–230 (2001) 988; H.R. Salva, P. Monceau, A. Ghilarducci, S. Seiro, M. Saint Paul, P. Lejay. Physica B 320 (2002) 97] , with activation enthalpies between 4 and 6eV. We analyse both the increase of IF maxima and relaxation strength with the increase of the substitutional atom size (1.26, 1.39 and 1.56Å for Ca, Sr and Ba atoms, respectively); and with the increase of the Goldschmidt tolerance factor. This behaviour is comprehensible because the intensity of the Zener relaxation depends on the distortions introduced by pairs of substitutional atoms. [Copyright &y& Elsevier]

Abstract: We have performed electrical resistivity and DC magnetization measurements as a function of temperature, on polycrystalline samples of phase-separated La5/8− y Pr y Ca3/8MnO3 (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. [Copyright &y& Elsevier]

Abstract: We present the electrical transport properties of single manganite–metal interfaces, at different temperatures. Each interface possessed an area of several square microns, and its electrical properties were isolated using a Kelvin bridge device that was fabricated from a bilayer grown entirely by pulsed laser deposition. Each bilayer comprised metals (Au, Ag and Ti) deposited in situ onto epitaxial La0.70Ca0.30MnO3 films. [Copyright &y& Elsevier]

Abstract: Magnetization measurements in La0.225Pr0.40Ca0.375MnO3 allowed us to construct an H–T phase diagram of this prototype phase-separated manganite. Magnetic relaxation results clearly demonstrate the dynamic nature of the phase-separated state. Our results showed the existence of large relaxation effects, and the relative fraction of the coexisting phases rapidly changes as a function of time. Through a thermodynamic phenomenological model, it is possible to interpret the experimental results, both static and dynamic, of the phase-separated system. The phase diagram resulting from this model is presented, including the static and dynamic properties characteristics of the phase-separated state in manganites. [Copyright &y& Elsevier]

Abstract: We have measured the pressure sensitivity of magnetic properties on nanostructured powders. Samples were synthesized following a microwave assisted denitration process and a final heat treatment at different temperatures to control the grain size of the samples. A span in grain diameters from 40nm to was obtained. Magnetization curves as a function of temperature were measured following different thermomagnetic histories. AC susceptibility as a function of temperature was also measured at different hydrostatic pressures (up to 10kbar) and for different frequencies. Our results indicate that the nanostructuration plays a role of an internal pressure, producing a structural deformation with similar effects to those obtained under an external hydrostatic pressure. [Copyright &y& Elsevier]

Abstract: The possibility of different types of magnetic polarons (ferrons) is discussed for an antiferromagnetic (AF) chain doped by non-magnetic donor impurities. The conduction electrons are assumed to be bound by the impurities. It is shown that two types of ferrons can exist in such a system: ferrons with the sizes of the order of the localization length of the electron near the impurity, and those with more extended distortions of the AF order in the chain. The ferrons of the first type correspond to the ground state, whereas ferrons of the second type can be treated as metastable excitations. The energy of the excited states decreases with the growth in density of impurities. This is a signature of an attractive interaction between ferrons, which could provide a possible mechanism for a large-scale phase separation in manganites and related compounds. [Copyright &y& Elsevier]

Abstract: We investigate possible ground states and spin excitations in the model of effective Mn–O–Mn polarons, for different values of magnetic interactions on a frustrated triangular lattice. The spin waves show a crossover between possible magnetic ground states, with either A-type or CE-type antiferromagnetic order, or spiral phases. [Copyright &y& Elsevier]

Abstract: The electrical resistivity , Seebeck coefficient S and magnetization M have been measured for polycrystalline Pr0.65Ca0.35Mn0.96A0.04O3-doped with a vast variety of elements A. The ferromagnetic metal (FM) phase has been caused by doping only by Cr, Co, Ni, Ru and Ir. A necessary condition for the electronic configuration of the dopants has been clarified to materialize the FM phase in this system. [Copyright &y& Elsevier]

Abstract: Mn NMR spectra have been measured for the first time in the A-site ordered whose ground state is of antiferromagnetic insulator, and whose ground state is of ferromagnetic metal. These spectra consist of several much narrower lines compared with those observed in the A-site disordered . [Copyright &y& Elsevier]

Abstract: From resistivity specific heat (measured at and 9T) and thermoelectric power measurements on La1−xPrxSr2Mn2O7, , we find the electronic and the thermal transport in these materials to be predominantly two-dimensional. The localization especially at low temperatures increases with Pr concentration. For , the relative proportion of CE-phase grows with , and becomes unstable for between 120&#60;T&#60;160K. [Copyright &y& Elsevier]

Abstract: We have examined the infrared reflectivity and the electrical resistivity of La1− x [Sr(Ba)] x Mn1– z [Cu(Zn)] z O3 samples in ferromagnetic metallic and insulator regime. Several phase transitions are observed, the most obvious being the transition from a ferromagnetic metallic to a ferromagnetic insulator phase that is related to the formation of short-range orbitally ordered domains. The temperature T 1 of the phase transition is dependent on doping concentration and for optimally doped samples (~32% of Mn4+ ions) we have found T 1≈0.93 T C. [Copyright &y& Elsevier]

Abstract: We investigate the 2D ferromagnetic Kondo lattice model for manganites with classical corespins at Hund''s rule coupling , with antiferromagnetic superexchange . We employ canonical and grand canonical unbiased Monte Carlo simulations and find paramagnetism, weak ferromagnetism and the flux phase, depending on doping and on . The observed single-particle spectrum in the flux phase differs from the idealized infinite lattice case, but agrees well with an idealized finite lattice case with thermal fluctuations. [Copyright &y& Elsevier]

Abstract: We describe the magnetic phases of hexagonal rare-earth manganites RMnO3 using Landau theory. A minimal model based on four 1D magnetic order parameters is developed. [Copyright &y& Elsevier]

Abstract: The NMR spectra demonstrate that the ground state of the A-site ordered manganite is the coexistent one of the ferromagnetic and antiferromagnetic domains, which are assigned to the metal and the insulating charge-ordered states, respectively. The ferromagnetic domain in is identical to the bulk ferromagnetic metal phase of the disordered , irrespective of the absence of A-site disorder. [Copyright &y& Elsevier]