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Abstract: Pure and some copper doped (x =0.01, 0.05, 0.1) ceramic specimens of K2Ti6O13 were synthesised using solid-state route. Lattice constants determined from room temperature XRD data revealed its single phase formation in a monoclinic symmetry. X-band EPR-data, recorded at RT, revealed the substitution of Ti4+ lattice sites by two different copper species corresponding to their distinct locally distorted environments. Dielectric data revealed the role of defect associate dipoles identified as low-field signals (g ∼5.43) in the EPR-spectra on the ferroelectric–paraelectric type phase transitions recognized in the ɛ r(T) plots for all the compositions with distinct T C. Dielectric loss mechanism included space charge polarization, dipole orientation, and electrical conduction. Structural configuration was found to favour polaron conduction and impede the intratunnel ionic conduction. Moreover, electron-hopping conduction was dominant in the low-temperate region whereas intratunnel ionic conduction prevailed at higher temperatures. [Copyright &y& Elsevier]

Zero field cooled spontaneous exchange bias (SEB) is observed in self-assembled nanocomposite thin films of La 0.7 Sr 0.3 MnO 3 (LSMO):NiO grown on single crystal line SrTiO 3 (001) substrate by pulsed laser deposition. SEB is displayed by the asymmetry in the hysteresis loop of the composite film along with the field cooled conventional exchange bias (CEB) effect. The training effect shows that exchange bias relaxation is disorder mediated. It is revealed from DC magnetization measurements that such nanocomposite film divulges spin glass like behaviour, arising due to competing ferromagnetic and antiferromagnetic interactions at the assorted interfaces of ferromagnetic LSMO and antiferromagnetic NiO. X-ray magnetic circular dichroism (XMCD) measurements discern that SEB is mainly originating due to ferromagnetic coupling of unstable interfacial antiferromagnetic spin due to NiO with the ferromagnetic LSMO at the disordered interface. These results of self-assembled thin films provide a useful input to realize and understand microscopic origin of SEB for device application. • Self-assembled nanocomposite thin films of La 0.7 Sr 0.3 MnO 3 (LSMO):NiO grown on SrTiO 3 (001). • Zero field cooled spontaneous exchange bias (SEB), field cooled conventional exchange bias (CEB). • The training effect shows that exchange bias relaxation is disorder mediated. • Magnetization measurements reveals the presence of interfacial disordered glass like behaviour. [ABSTRACT FROM AUTHOR]

Hexagonal Sr 0.6 Ba 0.4 MnO 3 (SBMO) follows P 6 3 / mmc symmetry where MnO 6 octahedra are both face-shared (Mn 2 O 9 bioctahedra) and corner-shared via oxygen anion. It undergoes ferroelectric (FE) and antiferromagnetic (AFM) orderings close to the room temperature. Magnetic properties appear to be governed by intricate exchange interactions among Mn4+ ions within and in adjacent Mn 2 O 9 bioctahedra, contingent upon the local structural changes. Calculations based on our model spin-Hamiltonian reveal that the dominant linear AFM fluctuations between the Mn4+ ions of two oxygen-linked bi-octahedra result in short range correlations, manifest as a smooth drop in magnetization below 325 K. Competition between spin-exchange and local-strain is reckoned as responsible for the atypical magneto-electricity, obtained near the room temperature. • An incipient ferroelectric (FE) with magnetic anomaly nearby room temperature. • Improper-FE is owed to the locally-unequal Mn–O bond lengths in the MnO 6 octahedra. • Short range stabilization of dipoles with short range magnetic ordering. • Mn-displacement soft-vibration mode is coupled to the spin ordering in the material. • Frustration involving spin-exchange and local-strain is responsible for the ME. [ABSTRACT FROM AUTHOR]

We report the results of the studies on crystal structure, electronic structure and dielectric properties of Er 1-x La x FeO 3 (ELFO) (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) orthoferrites synthesized by co-precipitation method. Rietveld refinement of the XRD data confirms the orthorhombic crystal structure for all the samples. The study of Fe L 3,2 -edge X-ray Absorption spectroscopy shows the presence of Fe-ions in 3 + valence state in all the samples. Investigations on the dielectric behavior of ELFO samples over the wide frequency range of 20 Hz to 5 MHz show the increment in the dielectric constant with La-doping. ErFeO 3 has the lowest value of dielectric constant whereas LaFeO 3 has the highest value of dielectric constant among all the samples. Effect of grain and grain boundary contribution on the dielectric behavior is studied using complex dielectric permittivity. The observed colossal dielectric behavior in LaFeO 3 is attributed to the combined contribution from the intrinsic dielectric constant of the material and that due to the modification in the microstructure. • Synthesis of La-doped ErFeO 3 orthoferrites using co-precipitation method. • Effect of La-doping on the room temperature dielectric behavior. • Role of microstructure on the dielectric properties of orthoferrites. [ABSTRACT FROM AUTHOR]

Abstract In this work, a series of Dy3+ (0.25, 0.5, 1, 1.5, 2, 2.5 mol. %) doped Mg 2 P 2 O 7 phosphors were synthesized via solution combustion method. The crystal structure and phase purity of phosphor were identified by X-ray diffraction technique. The lattice parameters was obtained from Rietveld refinement and found to be a = 13.15 Å, b = 8.297 Å and c = 9.039 Å for Dy3+ (1.5 mol. %) doped Mg 2 P 2 O 7. X-ray photoelectron spectroscopy was used to examine the elemental composition and oxidation states of the phosphor. Optical properties of phosphor were analyzed using Photoluminescence and UV–Vis spectroscopy. Three emission bands in visible region at 482, 574, and 663 nm were observed when excited under near-UV (348 nm) wavelength, that corresponds to the electronic transitions 4F 9/2 → 6H 15/2 , 4F 9/2 → 6H 13/2 and 4F 9/2 → 6H 11/2 of Dy3+ ion, respectively. The optimized concentration of Dy3+ ion is observed at 1.5 mol. %. The concentration quenching occurs due to dipole-dipole interaction mechanism between the dopant ions. A band gap of 5.4 eV estimated from diffuse reflectance spectrum. Graphical abstract Image 1 Highlights • Synthesis of Dy3+ doped Mg 2 P 2 O 7 phosphors via solution combustion method. • XRD and FTIR's spectroscopy used for structure confirmation. • The electronic states of Mg, P, O and Dy are confirmed by XPS. • Optical properties of phosphor were analyzed using Photoluminescence and UV–Vis spectroscopy. [ABSTRACT FROM AUTHOR]

Abstract Magneto-electric and electronic properties of Nd 1- x Sr x MnO 3-δ (0.3 ≤ x ≤ 0.7) (NSMO) nanoparticles are investigated. NSMO nanoparticles are synthesized by glycine assisted auto combustion method. The structural and morphological properties are probed using X-ray Diffraction (XRD) and Field Emission Scanning Electron Microscopy (FESEM). NSMO crystallizes in orthorhombic structure and nearly spherical agglomerated morphology is observed. Resistivity of the order of few MOhm-cm is recorded for all the compositions and the transport mechanism is interpreted by using Mott variable range hopping (VRH) model. In absence of magnetic field all samples show insulating nature over the studied temperature region (300- 5 K), while Metal to Insulator transition is observed in the presence of magnetic field (8T). Large Colossal Magnetoresistance (CMR) is noticed below 50 K for NSMO. Observed Curie temperature is in the range of 102–115 K and it is found to be independent of Strontium doping concentration. Bifurcation in FC-ZFC, for all the samples, is at higher temperature than blocking temperature (∼72 K) indicates glassy state. We have calculated thickness of magnetic dead layer by two different ways and it lies between 1.6 and 2.9 nm. Concentration of divalent element and oxygen non-stoichiometry affects the relative fraction of Mn3+/Mn4+ ions. Mn3+/Mn4+ in our samples is determined from areas under the deconvoluted X-Ray Photoelectron Spectra (XPS) of Mn core level. The Mn3+/Mn4+ ratio is higher than the value expected from nominal composition, which indicates oxygen non-stoichiometry. Oxygen non-stoichiometry is also confirmed by chemical titration method. Highlights • Synthesis of NSMO nanoparticles by glycine assisted auto combustion method is presented. • Effect of particle size and surface stress on unit cell volume is examined. • VRH mechanism, Abeles model, oxygen deficiency and core shell model are used to explain transport properties. • Magnetic properties of NSMO nanoparticles are discussed by considering magnetic dead layer. • Oxygen non-stoichiometry is probed by XPS and Iodometric titration. [ABSTRACT FROM AUTHOR]

The present work reports preparation of polycrystalline G d F e 1 − x M n x O 3 (x = 0.0 to 0.5) samples with solid-state reaction method and characterization using x-ray diffraction, 57 Fe Mössbauer spectroscopy, magnetization measurements, leakage current density and soft x-ray absorption spectroscopy measurements. Although F e 3 + and M n 3 + have similar ionic radii, noticeable variations in lattice parameters are seen which are attributed to local distortions introduced by Jahn-Teller active M n 3 + doping. Antiferromagnetic transition temperature corresponding to F e 3 + ordering ( T N , F e ) and G d 3 + ordering ( T N , G d ) is found to decrease with Mn doping, which could be due to weakening of Fe-Fe interaction and Gd-Gd interactions respectively. The Mn substitution at Fe site in G d F e O 3 is found to induce F e 3 + spin reorientation transition ( T S R T ) at a critical concentration and T S R T is found to increase with the Mn doping. Temperature dependent 57 Fe Mössbauer measurements have been carried out to study the local distortions by estimating quadrupole shift, the evolution of magnetism and also the spin reorientation transition in G d F e O 3 with Mn doping. Leakage current density is found to increase with Mn doping in G d F e O 3 , initially very fast and almost saturating for higher concentrations of Mn doping due to the formation of multiple oxidation states of dopant Mn at lower concentrations as evidenced from soft x-ray absorption spectroscopy measurements. [ABSTRACT FROM AUTHOR]

The electronic properties of (1 1 1) oriented Cr doped Eu 2 O 3 thin film has been studied using the x ray absorption and photoemission spectroscopic techniques. Cr-2 p core level XPS and Cr- L edge XAS results confirm the 3+ ionic state of Cr, that precludes the formation of Cr metal clusters in the film. The modification in the electronic structure due to Cr doping is probed by the resonant photoemission spectroscopy measurements using variable photon energy sources at Eu 4 d → 4 f and Cr 3 p → 3 d photo absorption region. The valence band spectra (at 145 eV) shows drastic change in the intensity of feature close to Fermi level along with an additional feature in Cr doped film when compared with the valence band spectra of the undoped film. [ABSTRACT FROM AUTHOR]

Herein, we have investigated the electronic properties of Fe doped Eu 2 O 3 thin film using x-ray absorption spectroscopy (XAS), valence band spectroscopy and resonant photoemission spectroscopy (RPES). The Fe L 3, 2 edge XAS spectra confirms the “3+” ionic state of the Fe in the film. The valence band spectrum of Fe doped film shows an enhancement in the intensity of feature “A” close to Fermi level and origin of another feature “E” at 11.1 eV. The valence band spectroscopy measurements have been performed at the energies in the Eu 4 d → 4 f and Fe 3 p → 3 d photo absorption region that clearly disentangles the features in valence band to be of either Eu and Fe hybridized with O or to be of Eu and O only. [ABSTRACT FROM AUTHOR]

Resonant photoemission spectroscopy has been used to investigate the character of Fe 3 d states in FeAl alloy. Fe 3 d states have two different character, first is of itinerant nature located very close to the Fermi level, and second, is of less itinerant (relatively localized character), located beyond ∼2 eV below the Fermi level. These distinct states are clearly distinguishable in the resonant photoemission data. Comparison between the results obtained from experiments and first principle based electronic structure calculations show that the origin of the itinerant character of the Fe 3 d states is due to the ordered B 2 structure, whereas the relatively less itinerant (localized) Fe 3 d states are from the disorders present in the sample. The exchange splitting of the Fe 3 s core level peak confirms the presence of local moment in this system. It is found that the itinerant electrons arise due to the hybridization between Fe 3 d and Al 3 s and 3 p states. Presence of hybridization is observed as a shift in the Al 2 p core-level spectra as well as in the X-ray near edge absorption spectra towards lower binding energy. Our photoemission results are thus explained by the co-existence of ordered and disordered phases in the system. [ABSTRACT FROM AUTHOR]

In this study, the polycrystalline sample of La 0.5 Ca 0.5 MnO 3 (LCMO) with perovskite (Orthorhombic) crystalline structure was synthesized by citrate gel method. The temperature dependent magnetization studies exhibit both paramagnetic to ferromagnetic and ferromagnetic to antiferromagnetic transition of LCMO at ∼230 K and ∼150 K, respectively. The X-ray photoemission spectroscopy data revealed electronic structures, chemical properties, while the valence band photoemission spectra for LCMO measured at various photon energies ranging from 40 eV to 60 eV, showed Fano curve like resonance behavior for Mn 3 p to 3 d transition and also confirmed the change of DOS near Fermi level. [ABSTRACT FROM AUTHOR]

Relationship between magnetism and structure of Cu-doped ZnO was investigated at macroscopic and microscopic levels. Thin Zn 1−x Cu x O films ( x = 0.02, 0.04, 0.07 and 0.10) were prepared by a pulsed laser deposition and characterized via superconducting quantum interference device (SQUID) magnetometry, high-resolution x-ray diffraction, and Cu K -edge and Zn K -edge x-ray absorption, x-ray linear dichroism and x-ray circular magnetic dichroism spectroscopy. Even though the samples exhibit room-temperature ferromagnetism with magnetization that increases with Cu concentration, we did not detect signatures of local magnetic moments associated with Cu atoms, as evidenced by the lack of any XMCD signal. The host ZnO wurtzite lattice is not significantly altered by the addition of Cu. At the same time, most of the Cu atoms are not incorporated into the wurtzite lattice but rather have a CuO-like coordination. These results indicate that ferromagnetism of the investigated Zn 1−x Cu x O films is not directly linked to the doping atoms but rather is due to some other changes which have been introduced to the host ZnO by the dopants. [ABSTRACT FROM AUTHOR]

In the present work, important information on crystalline structure and band offset of InAs/Ge heterojunction epitaxially grown directly on Ge (111) substrate is presented. As revealed by high resolution x-ray diffraction (HRXRD) and Raman measurements the InAs nanostructures are highly crystalline and oriented with the substrate having predominantly zinc-blende (ZB) structure. The relaxation ratio of grown layer is of 95%. The lateral and vertical coherence lengths are estimated to be ∼65 nm and ∼14 nm, respectively, which closely match with atomic force microscopy results. As revealed from HRXRD experiments, two domains/sub-lattices of ZB InAs (111) structures having different stacking configurations were found to coexist. A band diagram is constructed for InO/InAs/Ge system. Valence band offset of 300 meV and conduction band offset of 20 meV for InAs/Ge have been determined. Hence, InAs/Ge (111) system can have potential application in low power devices. [ABSTRACT FROM AUTHOR]

The electronic structure of a ferromagnetic Heusler alloy Co 2 MnSn has been investigated using resonant photoemission spectroscopy to probe the Mn 3 d and Co 3 d states in the valence band region. The motivation of the present work is to understand the low value of spin polarization reported for this system, which mainly depends on the density of states present at the Fermi level. Valence band of Co 2 MnSn shows a large density of delocalized Co 3 d states present near the Fermi level. The Mn 3 d states are more localized and exist below the Fermi level. First principles calculations using density functional theory with GGA and GGA + U formalisms have been performed to understand and analyze the experimental results. The experimental density of states and magnetic moment show a good matching with the calculation carried out with on-site Coulomb correlation U of ∼3 eV on the Mn 3 d states. The presence of U on the Mn 3 d states also reduces the spin polarization at the Fermi level, which is one of the reasons for the observed low value of spin polarization reported for this system. [ABSTRACT FROM AUTHOR]

Highlights: [•] Sol–gel grown polycrystalline single phasic Zn1 − x Co x O system is synthesized. [•] X-ray Photoemission spectroscopy reveals that, Co-substitution results in the EF shift and chemical shift in ZnO. [•] Co-substitution induced electronic structure and valence band modifications in Zn1 − x Co x O (x =0, 0.5 and 0.15) samples. [•] Co 3d states around 3.4eV show resonance at ∼62eV and are hybridized with O 2p bonding states. [ABSTRACT FROM AUTHOR]

• Oxygen vacancies (V O) in SrRuO 3 (SRO) lead to enhanced correlation strength (U/W). • V O causes a reduced DOS at E F and reduced internal magnetic field strength. • Resistivity upturn at low temperatures is observed in SRO thin-film owing to V O. • Quantum effects are observed in Oxygen- deficient SRO thin-film. • At low temperatures, WL prevails over REEI in oxygen-deficient SRO thin-film. [Display omitted] Herein, the electronic, magnetic, and transport properties of an oxygen-deficient epitaxial SrRuO 3 (SRO) thin film have been investigated. The oxygen vacancies (V O) in the SRO thin-film transform a fraction of Ru4+ ions into Ru3+, resulting in an enhancement of the unit cell volume. Due to the elongated lattice parameters, the electronic bandwidth decreases and gives rise to the enhanced correlation strength. Further, distinctive effects of V O are seen in the temperature-dependent resistivity behavior [ ρ (T)]. At low temperatures, the SRO thin film exhibits a resistivity minima near 48 K along with the ferromagnetic to paramagnetic transition (T C ~ 150 K). The resistivity upturn at low temperatures is analyzed using quantum correction in the conductivity and it is found that the weak localization prevails over renormalized electron-electron interactions in the low-temperature resistivity upturn behavior of oxygen-deficient (V O) SRO thin film. [ABSTRACT FROM AUTHOR]

Abstract: Zinc oxide thin films are grown by successive ionic layer adsorption and reaction technique at room temperature. The as-grown films were annealed at different temperatures, viz. 350, 400, 450, and 500°C in air atmosphere for 2h. Effect of annealing on the physical properties of ZnO thin films has been studied. XRD analysis reveals the polycrystalline nature for ZnO thin films with hexagonal phase. The films were highly oriented along (100) and (101) planes, an enhancement in these peaks is the significance of the post-deposition annealing treatment on ZnO thin films. The optical studies of the samples show that the energy band gap was decreased in accordance with the annealing temperature. The results of optical studies were strengthened by photoluminescence (PL) studies. [Copyright &y& Elsevier]

Abstract: In the present work, the effect of Zr on the hydrogenation behaviour of CeNi5 intermetallic compound has been studied. All intermetallic compounds have been synthesized by arc melting method in the argon atmosphere and well characterized by the means of XRD and SEM. The elemental composition of each sample has also been investigated using EDX technique. EDX spectrum confirms the elements present in the sample and the exact quantitative composition of these elements. The lattice constant and volume was found to increase with Zr substitution. Pressure composition isotherm has been carried out for CeNi5−x Zr x (x =1, 2) alloys in the temperature and pressure ranges of 293≤ T ≤333K and 0.5≤ P ≤35bar, respectively. The plateau pressure was found to reduce significantly, which makes these alloys more useful for practical applications in comparison to parent alloy (CeNi5). The enthalpy and entropy for the systems has been calculated using Van’t Hoff plot. [Copyright &y& Elsevier]

Abstract: The effect of partial substitution of Ni by Cr in CeNi5 intermetallic compound has been studied by pressure–composition isotherm measurements for different temperatures. The samples were prepared of high purity materials using the standard arc melting technique in argon atmosphere. The structure and the elemental composition of different alloys have been investigated by means of XRD, SEM and EDX techniques. The unit cell volume of the alloy was found to increase with increasing Cr content. In order to calculate the hydrogen storage capacity pressure–composition isotherm has been investigated for CeNi5−x Cr x (x =1, 2) alloys in the temperature and pressure ranges of 293≤ T ≤333K and 0.5≤ P ≤35bar, respectively. The P–C–T isotherm for different alloys clearly shows the presence of three regions α, α + β and β. The enthalpy and entropy for the systems has also been calculated using Van’t Hoff plot. The variation of enthalpy and entropy with hydrogen content has also been studied. [Copyright &y& Elsevier]

Structural and magnetic response of Ni 1-x Cr x Fe 2 O 4 (x = 0 and 0.05) are presented using X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR) and SQUID magnetometer. The single phase of both the compositions is confirmed using Rietveld refinement method. The absence of any impurity is further cinched using structural sensitive techniques, namely FTIR and Raman spectroscopy. Interestingly, a pinched shaped M − H behaviour is observed for the Cr doped ferrite. In addition, we have computed magnetic moment, Mulliken's population, density of states (DOS) and Compton profiles (CPs) for NiFe 2 O 4 using linear combination of atomic orbitals (LCAO) scheme with and without hybrid functional for exchange and correlation potentials. Further, theoretical CPs have been validated using isotropic CP measurement with 137Cs radio-isotope for NiFe 2 O 4. Among the considered exchange-correlation potentials within LCAO, the hybrid B3LYP scheme based momentum densities give better agreement with the experimental CP. Majority- and minority-spin DOS have confirmed the insulating nature of NiFe 2 O 4. Peculiarities of presently deduced MP data and magnetic moments are also discussed. Image 1 • Structural and magnetic response of NiFe 2 O 4 and Ni 0.95 Cr 0.05 Fe 2 O 4 using X-ray diffraction, Raman spectroscopy, FTIR spectroscopy and SQUID magnetometer. • Confirmation of impurity less single phase for both compositions by Rietveld refinement method, FTIR and Raman spectroscopy. • Computed magnetic moment, Mulliken's population, density of states (DOS) and Compton profile (CP) for NiFe 2 O 4 using LCAO with and without hybrid functional. • Validation of LCAO-B3LYP scheme for NiFe 2 O 4 using isotropic CP measurements with 137Cs radio-isotope and M-H measurements. • Analyzed spin dependent DOS and confirmation of wide band gap nature of NiFe 2 O 4 and projected use of LCAO approximations for deducing magnetic response. [ABSTRACT FROM AUTHOR]

Temperature dependent spin momentum densities of polycrystalline CoCr 2-x Fe x O 4 (x = 0.4 and 1) with inverse spinel structure have been measured using magnetic Compton spectrometer. Estimated site specific and absolute spin moments are compared with the magnetization measurements to deduce the orbital magnetic moments. To supplement the present magnetic Compton scattering data, spin-polarized relativistic band structure calculations employing Korringa-Kohn-Rostoker Green's-function formalism have also been performed. Ferri-magnetic nature of CoCr 2-x Fe x O 4 (x = 0.4 and 1) systems have been explained on the basis of distribution of Fe and Co atoms between tetrahedral and octahedral sites. The suggested mixed spinel structure arrangement is supported by experimentally observed spin magnetic moments and minimum ground state energies which shows the potential of magnetic Compton spectroscopy in resolving the structural-cum-magnetic issues of such oxides. • Synthesized polycrystalline samples of CoCr 2-x Fe x O 4 (x = 0.4 and 1). • Role of Fe in amending magnetism is explored using MCS and magnetization measurements. • Increase in total magnetic moment and Tc are observed on increasing Fe doping. • Feasibility of Co and Fe atoms at oct and tet sites incorporated in SPR-KKR method is Validated by MCS. • Cr atoms prefer oct site while Co atoms can distribute over oct and tet sites on doping of Fe. [ABSTRACT FROM AUTHOR]