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Transport and magnetic measurements were used to examine the doping of La-site in R 0.7 Ca 0.3 MnO 3 by mixed rare earths. Magnetization and electrical transport properties are significantly impacted by partially mixed rare earth doping at La-site. Mixed rare earth doped sample displays exceptional thermal and magnetic hysteresis effects at the temperature range where the high magneto-resistance is found. The Current – Voltage characteristics I-V curves of R 0.7 Ca 0.3 MnO 3 (R = La 0.233 Pr 0.233 Nd 0.233) sample shows nonlinear conduction i.e. negative differential resistance (NDR), which is due to the appearance of metallic filaments. Moreover the strong hysteresis in both resistivity ρ(T) and magnetization M(T) curves ascribed to creation of a co-existing magnetic phase exists in mixed rare earths at La-site doping. [ABSTRACT FROM AUTHOR]

To study the effect of manganese non-stoichiometry at B-site, a series of manganites with compositional formula La 0.67 Sr 0.33 Mn 1±x O 3 (where x = 0, 0.05 and 0.1) was synthesized by oxalate precursor method. X-ray diffraction data confirm the rhombohedral structure of La 0.67 Sr 0.33 Mn 1±x O 3 along with minor phases of Mn 3 O 4. The average grain size is found to be 266 nm for x = 0 whereas its magnitude decreases with excess or deficiency in manganese concentration. An increase in the manganese non-stoichiometry leads to the coexistence of ferromagnetic and antiferromagnetic interactions. The effect of Mn 1±x on the magnetotransport properties could be understood on the basis of collective behaviour of magnetic spins, double exchange mechanism and ratio of Mn4+/Mn3+ ions. A crossover from negative to positive magnetoresistance behavior above metal-insulator transition temperature was observed for LSP-0.95 sample, whereas a positive magnetoresistance over the entire temperature region was noticed for LSP-1.10 sample. [ABSTRACT FROM AUTHOR]

• Ion beam modification has been studied for CoFe/n-Si interfaces. • Ordered array of grains has been observed which is due to recrystallization phenomenon. • Drastic change in M-H loops from antiferromagnetic coupled phase to ferromagnetic phase has been observed. • A significant electronic transport has been observed with and without magnetic field. • Magneto-resistance of ∼7% has been estimated for the structure. Interfacial structures of ferromagnetic (FM) metal combined with semiconductor (SC) are key step for realizing spintronic devices where spin degree of freedom can also be utilized in addition to the charge of electron. Tailoring of such interfaces (of FM/SC) is known to tune the magnetic, optical, structural and transport properties. Swift heavy ion irradiation (SHI) can be used as a potential tool to tailor the interfaces. In our present work, effect of ion beam irradiation (100 meV Ni+7 ions) on the CoFe/n-Si interfacial structures had been studied. Thin films of CoFe was deposited by electron beam evaporation technique using CoFe metallic alloy on Si substrate. The realized interfacial structure was characterized from structural, morphological and magnetic point of view. The surface exhibits grainy structure with very fine domain (∼50 nm) on the irradiation. Electronic transport study across the interface shows an increase in current on irradiation with significant magnetic field sensitivity and a magnetoresistance of ∼7% has been observed. The observed results of increased magnetization and enhanced magnetic field sensitivity has been understood in the realm of irradiation induced interfacial intermixing across the interfaces. The chemical phases formed and nature of the interface as a result of irradiation was probed by X-ray photoelectron spectroscopy (XPS) study which confirms the formation of various silicide phases along with the metallic phase. The results were also compared with our earlier studies [15–16] on CoFe/n-Si system and found that fluence of 1 × 1011 ions/cm2 seems significant to result in interesting magnetic and transport properties without much damage to interface. [ABSTRACT FROM AUTHOR]

Double perovskite (DP) oxide material receive extensive research interest due to exciting physical properties with potential technological application. 3 d based DP oxides are promising for exciting physics like magnetodielectric, ferroelectric, Griffiths phase, etc., specially Co/Mn DPs are gaining much research interest. In this paper we present the study of magnetic phase and transport properties in nano-crystalline Pr 2 CoMnO 6 a 3 d based double perovskite compound. This material shows a paramagnetic (PM) to ferromagnetic (FM) phase transition below 173 K marked by a rapid increase in magnetic moment due to spin ordering. We found divergence in inverse magnetic susceptibility (χ − 1) from Curie–Weiss behavior around 206 K which indicates the evolution of Griffiths phase before actual PM-FM transition. We found that the Griffiths phase suppressed with increasing applied magnetic field. For the understanding of charge transport in this material we have measured temperature dependent electrical resistivity. Pr 2 CoMnO 6 is a strong insulator where resistivity increase abruptly below magnetic phase transition. To understand the effect of magnetic field on transport behavior we have also measured the magnetoresistance (MR) at different temperatures. Sample shows the negative MR with maximum value ∼22% under applied magnetic field of 50 kOe at 125 K. MR follows quadratic field dependency above T c however below T c the MR shows deviation from this field dependency at low field. • Pr 2 CoMnO 6 shows paramagnetic to ferromagnetic phase transition around 173 K. • Griffiths phase is observed in this material marked by deviation in magnetic susceptibility. • Pr 2 CoMnO 6 is a strong insulator where resistivity shows inverse temperature dependency. • Material shows large magnetoresistance below T c ∼ 22 % in 50 kOe at 125 K. [ABSTRACT FROM AUTHOR]

The parametric torque presents a promising recording mechanism for MRAM, complementing Spin Transfer Torque and Spin Orbit Torque, enabling magnetization reversal in a nanomagnet using a DC electrical current. Its resonance nature allows for optimization of magnetization reversal at a lower current, presenting an opportunity for a lower recording current and, therefore, for efficient and high-performance operation in modern MRAM technology. The in-plane magnetic field generated by spin accumulation serves as the driving force behind this torque. Experimental measurements of the current-induced in-plane magnetic field in the FeB nanomagnet reveal its magnitude to be around 40 Gauss at a current density of 25 mA/ μ m 2 , a value adequate for facilitating parametric magnetization reversal. The parametric torque is analytically calculated by solving the Landau–Lifshitz equation. Analytical calculations demonstrate its potential in advancing modern MRAM technology. • A novel resonance torque capable of magnetization reversal via DC electrical current is introduced. • Parametric torque, complementing Spin Transfer Torque and Spin Orbit Torque, enhances MRAM's recording capabilities. • Unlike Damp-Like and Field-Like torques, Parametric torque occurs only under specific identified conditions. • Experimental measurement of the spin-accumulation-induced magnetic field in a FeCoB nanomagnet is presented. • Parametric torque is analytically calculated via a solution of Landau–Lifshitz equation. [ABSTRACT FROM AUTHOR]

• Ca 4 Mn 3-x W x O 10 (x = 0, 0.05, 0.10) synthesised using a solid-state reaction technique. • Rietveld refinements of high-quality powder XRD show good convergences. • X-ray photoelectron spectroscopy show the mixed oxidation state of Mn cations. • Semiconducting behaviour of the samples is consistent with the VRH and SPH models. • Thermopower study reveals that all samples have a small polaron hopping mechanism. This report comprehensively investigates the crystal structure, magnetism, and transport properties of tungsten (W6+) substituted polycrystalline Ca 4 Mn 3-x W x O 10 (x = 0, 0.05, 0.1) compounds. The compounds were synthesized using the solid-state method and found to exhibit a single-phase orthorhombic structure confirmed by the Rietveld refinement. The substitution of (W6+) induces a change in the Mn octahedron and enhances the unit cell volume. The morphology indicates the crystalline nature of all the samples. The FTIR spectroscopic study revealed the position of the IR bands, which is highly sensitive to the oxidation state of Mn-ions. The shift to higher wavenumbers indicates reduced oxidation from Mn4+ to Mn3+ species. The appearance of the Mn4+ oxidation state in (x = 0) and the emergence of Mn3+ on W6+ substitution for (x = 0.05, 0.1) compounds are explored. The electrical resistivity plots revealed that compounds are semiconducting. The magnitude of resistivity decreases with W6+ substitution. The reported compounds exhibit a significant negative magneto-resistance towards lower temperatures. The compounds also demonstrate short-range ferromagnetic (FM) behavior attributed to the charge compensation effect's double exchange interaction (DE) connecting Mn4+ and Mn3+. The negative value of thermoelectric power (S) suggests the presence of charge carriers such as electrons, and the value of S first increased and then decreased in doped samples. The conduction in the studied compound is attributed to small polaron hopping. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Synthesis of bulk La 0.7 Ba 0.3 Mn 1−x Al x O 3 (0 ≤ x ≤ 0.15) compounds with Al3+ substitution at Mn-site. • Significant crystal structural-relaxations in terms of bond-length, bond-angle and tolerance factor values. • Methodological investigation of magneto-transport and thermoelectric properties. • Enhanced magnetoresistance and determination of several other electronic-transport parameters that govern charge conduction. • Analysis of thermoelectric power via five degree polynomial fit and SPH/VRH polaron hopping mechanism. Abstract This report presents the structural, magnetoresistance, electrical and thermal transport properties of Aluminium substituted La 0.7 Ba 0.3 Mn 1−x Al x O 3 (0 ≤ x ≤ 0.15) compounds synthesized by solid state reaction method. To obtain crystallographic parameters, the X-ray diffraction patterns are fitted in R-3c space group with Rietveld refinement method. The resistivity and magneto-transport measurements are performed using standard four-probe assembly with and without magnetic fields. The peak resistivity ρ peak is noted at Metal-Insulator Transition temperature (T MI) and lowering in T MI is observed for higher concentrations of Al3+. The resistivity data have been analyzed in two parts. Firstly, in the metallic region below T MI the resistivity data is fitted with three degree polynomial. Secondly, in the semiconducting region above T MI data have been fitted with Variable Range Hopping (VRH) and Small Polaron Hopping (SPH) models. The Seebeck coefficients found to be positive throughout the temperature range (10 K–300 K) with holes as dominating charge carriers. Similar to the resistivity profile, in metallic region the thermo-power is explained with qualitative model based on diffusion, magnon-drag, phonon-drag and spin fluctuation contributions whereas the semiconducting region is explained with small polaron hopping model. [ABSTRACT FROM AUTHOR]

Abstract In this study, we have investigated the crystallographic structure and the temperature-dependent resistivity of an electron doped La 1-x Zr x MnO 3 manganite system. X-ray photoemission spectroscopy (XPS) for core level study has been carried out to confirm the electron doping. The results of XPS core level study suggests that Zr ions are in the tetra-valent state and Mn ions are forced to be in a mixed state of Mn3+ and Mn2+. Rietveld refinement of X-ray powder diffraction results have confirmed the rhombohedral crystal symmetry of the samples with space group R-3c. The temperature dependent resistivity and magnetization plots exhibit insulator to metal transition (MIT) accompanied with Paramagnetic to Ferromagnetic transition (T c). Three independent MIT transitions have been observed, the first sharp transition at T P1 showed a strong correlation with the magnetic transition T c confirming that the intrinsic MIT happened at T P1. The insulating behaviour below T 1 has been attributed to the competition between the short range orbital/charge order and the long range FM order. The transition at lower temperature T P2 may be attributed to the percolative transport of charge carriers through ferromagnetic metallic domains. The third upturn transition assigned as T min has been ascribed to combined effect of electron-electron and Kondo interactions, the detailed qualitative analysis and discussion of which is under preparation. Highlights • Electron doped manganite system La 1-x Zr x MnO 3 were synthesized using solid state reaction method. • The system has a rhombohedral crystal symmetry with space group R-3c. • XPS core level study suggests electron doping of the system. • The system exhibits metal to insulator (MIT) transition accompanied by the Ferromagnetic (FM) to Paramagnetic (PM) transition. • Three independent MIT transitions have been observed, attributed to different physical phenomenon. [ABSTRACT FROM AUTHOR]

The electric and thermal transport properties (electric resistivity ρ, magneto-resistance MR , Hall coefficient R H and anomalous Hall effect, thermal conductivity Κ and Seebeck coefficient S ) of the off-stoichiometric Ni 1.92 Mn 1.56 Sn 0.52 Heusler alloy were measured in a wide temperature and magnetic field range. The simultaneous measurement of several transport and magnetic properties offers a possibility to combine information arising from the received experimental results. The phonon and the charge carriers parts of complex temperature dependence of thermal conductivity K(T) were consistently separated using the Lorentz factor and temperature dependence of resistivity ρ (T) . The positive values of the Hall coefficient R H has been determined in martensite phase of the alloy at low temperatures. R H reaches zero value at temperature range where the so-called “paramagnetic gap” was observed and the negative value of R H was detected in austenite phase. Temperature dependence of the Hall coefficient R H (T) was used to derive both, the density and the mobility of charge carriers. The standard relations were used to describe the measured temperature dependence of the Seebeck coefficient. All the received result point to an important role of changes in electronic structure of the alloy in all the studied transport effects. A scenario of the complex behavior of the transport properties of the Heusler alloy based on a possible existence of an energy gap in electronic structure is discussed. [ABSTRACT FROM AUTHOR]

Abstract In this paper, the resistivity of bilayer manganite LaSr 2 Mn 2 O 7 around the metal–insulator-like transition was systematically calculated as a function of temperature and applied magnetic field. A typical mathematical function (Gauss function) was used for fitting the experimental data. The theoretical values simulated in this work such as – metal–insulator transition temperature (T p) and maximum resistivity (ρ max) showed promising agreement with the experimental data. [ABSTRACT FROM AUTHOR]

Magnetism in dilute magnetic semiconductors (DMSs) has been a controversial topic since its discovery. There are many models which predict the origin of room temperature ferromagnetism (RTFM) in TM doped wide band gap semiconductors. Here, we report RTFM in chemically synthesized cubic Zn 1-x Ni x S (0 ≤ x ≤ 0.08) DMS nanoparticles of ∼3–5 nm size. Ferromagnetic behavior (at 300 K and 5 K) was found to increase with the increase in Ni doping concentration and was understood due to defect induced ferromagnetism. The low temperature magnetization measurement (ZFC-FC) shows that the nanoparticles are strongly coupled by magnetic interactions. Optical studies showed decrease in the energy bandgap along with the presence of sulfur and zinc vacancies and surface defects. Low temperature resistivity measurement depicted the semiconducting nature of the synthesized samples. With increase in doping concentration, an increase in the resistive behavior was observed which was explained in the realm of defects states created due to doping of the Ni ions. [ABSTRACT FROM AUTHOR]

SrIrO 3 (SIO) is one of the materials known to exhibit a high spin-orbit coupling with correlated semi-metallic ground state, along with the topological states, as proven in recent times. In this regard, the SIO thin films grown by us on SrTiO 3 (001) at certain deposition conditions, exhibit a low temperature magneto-transport behavior which is analogous to the materials with topological states. Further, we have explored various deposition conditions of SIO such as partial pressure of O 2 and different temperatures of growth for different thickness of SIO. In addition, from the electrical transport properties, SIO thin films found to exhibit semi-metallic nature with either insulating-like or a crossover from metal-like to insulating-like behavior based on the conditions chosen for the growth. Moreover, the magneto-transport data of various SIO thin films are found to be obeying the usual B 2 (Lorentzian) behavior in majority of the cases. At the same time, we have also observed the weak-localization and weak-antilocalization effects; along with a linear magneto-resistance at low temperature ranges. Thus, from our extensive measurements, it becomes clear that SIO thin films can exhibit wide varieties of magneto-transport properties based on the deposition conditions. Plethora of interesting properties exhibited by the highly spin-orbit coupled SIO epitaxial thin films at lower temperatures in the presence of magnetic field makes the material to be promising for the future applications in the field of spintronics. [ABSTRACT FROM AUTHOR]

This paper reports the synthesis of different particle size La 0.7 Sr 0.3 MnO 3 (LSMO) nanoparticles using non-aqueous sol gel synthesis route by calcination at temperatures 750 °C, 850 °C and 950 °C. In the present work, the effect of particle size of LSMO nanoparticles on its structural, magnetic and transport properties has been studied in detail. The X-ray diffraction analysis confirms the formation of LSMO nanoparticles having rhombohedral ( R 3 ̅ c ) structure with average particle size of 20 nm, 22.5 nm and 25.6 nm. An increase in magnetization and decrease in coercivity with increase in particle size is attributed to the magnetically disordered surface layer. The bifurcation in ZFC-FC magnetization indicates the possibility of spin glass like behavior of the LSMO nanoparticles. The effect of particle size on the resistivity and magnetoresistance were studied by using different conduction mechanism for different temperature regions. The upturn in the ρ-T curve at lower temperatures was explained by using Kondo-like transport mechanism. The maximum LFMR achieved was 32.3% at a field of 1 T at 10 K for 20 nm LSMO nanoparticle. [ABSTRACT FROM AUTHOR]

We report the effect of MgO phase on structural, electric and thermo electric properties of La 0.8 Sr 0.2 MnO 3 (LSMO) and manganite matrix-based composite series (1− x ) La 0.7 Ca 0.2 Sr 0.1 MnO 3 + ( x ) MgO with x = 0.0, 0.05, 0.10, 0.15 (abbreviated as LCSMO - MgO) synthesized by solid-state reaction method. X-ray diffraction (XRD) data infers that manganite LSMO compound possesses a rhombohedrally-distorted structure (space group R 3 c ), LCSMO has an orthorhombic structure ( Pnma space group) while to that MgO compound crystallizes in cubic structure (space group Fd3m ). XRD shows coexistence of MgO and La 0.7 Ca 0.2 Sr 0.1 MnO 3 phases in doped composites through their characteristic peaks. The temperature dependence of resistivity shows that the transport behavior of the composites is governed by the grain boundaries. These composites shows metal–insulator transitions at T = T MI which decreases with increasing MgO concentration. The magnetoresistance (MR) in this system increases with increasing MgO content, showing a maximum value (91% at 50 K and at lower fields) for (0.85) LCSMO - (0.15) MgO sample, which is larger than the largest MR value of pure La 0.7 Ca 0.2 Sr 0.1 MnO 3 (44% at 50 K). From thermoelectric power measurements, it is observed that electron-magnon scattering process is dominant mechanism in the low temperature region. [ABSTRACT FROM AUTHOR]

We report synthesis, structural details and electrical transport properties of topological insulator Bi 2 Te 3 . The single crystalline specimens of Bi 2 Te 3 are obtained from high temperature (950 °C) melt and slow cooling (2 °C/hour). The resultant crystals were shiny, one piece (few cm) and of bright silver color. The Bi 2 Te 3 crystal is found to be perfect with clear [00l] alignment. The powder XRD pattern being carried out on crushed crystals showed that Bi 2 Te 3 crystallized in R3̅m symmetry with a = b =4.3866(2) Å, c =30.4978(13) Å and γ =120°. The Bi position is refined to (0, 0, 0.4038 (9)) at Wyckoff position 6 c and of Te are (0, 0, 0) at Wyckoff position 3 a and at (0, 0, 0.2039(8)) at 6 c . Ambient pressure and low temperature (down to 2 K) electrical transport measurements revealed metallic behavior. Magneto transport measurements under magnetic field showed huge non saturating magneto resistance (MR) reaching up to 250% at 2.5 K and under 50 kOe field. Summarily, the short communication clearly demonstrates that Bi 2 Te 3 topological insulator exhibit non-saturating large positive MR at low temperature of say below 10 K. The non saturating MR is seen right up to room temperature albeit with much decreased magnitude. Worth mentioning is the fact that these crystals are bulk in nature and hence the anomalous MR is clearly an intrinsic property and not due to the size effect as reported for nano-wires or thin films of the same. [ABSTRACT FROM AUTHOR]

Structural, magnetic and magneto transport properties of La 1-y Sr y Mn 0.5 Co 0·5 O 3±δ perovskites prepared by aqueous solution combustion synthesis were studied in detail. The effect of Sr doping on the properties of these perovskites was investigated. As-prepared perovskites were characterized using X-ray diffraction for single phase formation. Magnetic study was carried out for in depth analysis of the magnetic properties. AC susceptibility study shows a change in the behavior of undoped and doped compounds in low temperature region. Ferromagnetic interactions was found to increase in the low temperature region in the doped compounds compared to that in the undoped compound. The measurements on resistivity showed reduction with Sr doping up to y = 0.5. This is attributed to the high spin stabilized Co3+ ions which enhance the ferromagnetic interactions and the hopping probability of e g charge carriers. [ABSTRACT FROM AUTHOR]

In the present paper we studied the structural, magnetotransport and thermopower properties of a series of polycrystalline La 0.7−x Sm x Ba 0.3 MnO 3 (0≤x≤0.2) compounds which were synthesized by conventional solid state reaction techniques. The Rietveld refinement of the X-ray diffraction pattern predicts the formation of single-phase compositions and doping of La 3+ by Sm 3+ ion converted the chemical structure form rhombohedral ( R-3C ) to orthorhombic ( Imma ) The scanning electron microscopy show clean smooth and densified structure images be a sign of good crystalline nature of the samples. The temperature dependent electrical resistivity is measured by standard four-probe method between 5 and 300 K exhibits Metal–Insulator Transition MIT which shows the decreasing trend with increasing Sm doping content and metallic state (TT p2 ) are explained within the framework of variable range hopping (VRH) and small polaron hopping (SPH) models. The application of magnetic field suppresses the resistivity in entire temperature range and with increasing the Sm 3+ content the samples showed very high magnetoresistance. The thermoelectric power (S) of the reported samples exhibit a crossover from positive to negative value and it increases in doped samples. The analysis of thermoelectric power data confirms the applicability of the small polaron hopping model in high temperature region and in low temperature fitted to an equation containing diffusion, magnon drag, phonon drag and electron-spin fluctuation term. An appropriate justification for the observed behavior is specified. [ABSTRACT FROM AUTHOR]

We investigated the electrical transport properties of epitaxial La 0.7 Ca 0.3 MnO 3 thin films grown by metal organic deposition process on LaAlO 3 single crystalline substrates. To explain the coexistence of ferromagnetic (FM)-metallic and paramagnetic (PM) -insulator phases in the same specimen, the temperature dependence of resistivity was simulated by the phenomenological percolation model which is based on the phase segregation of FM-metallic to PM-insulator. The temperature dependence of resistivity ( ρ ( T ) ) curves can be well fitted by ρ ( T ) = ρ FM f + ρ PM ( 1 − f ) with ρ FM is the resistivity of the FM phase below the Curie temperature ( T C ), ρ PM is the resistivity of the PM phase above T C and “ f ” is the FM volume fraction. The obtained fitting parameters have been correlated to the change in the strain in the films having various thicknesses. The ferromagnetic volume fraction ( f (T)) and the reduced magnetization m ( T ) show monotonic and “similar” behaviors. [ABSTRACT FROM AUTHOR]

We have synthesized a series of Sm 0.55 Sr 0.45−x Ag x MnO 3 (x = 0 & 0.15) by conventional solid state reaction method to scrutinize the effect of monovalent Ag + as a replacement of Sr 2+ ion on structural, electrical, magnetotransport and thermoelectric properties. The structural parameters obtained using Rietveld refinement of X-ray diffraction data which showed perovskite structure having orthorhombic ( Pnma ) symmetry without any detectable impurity phase. It is observed that M ZFC and M FC curves become more manifested as Ag + content is increased which indicates an increase in magnetic frustration arising due to bending of Mn-O-Mn bond. The M-H plots show the narrow hysteresis loops which indicate the soft ferromagnetic nature. Magnetic studies also show that the Curie temperature T C is found to decrease with Ag + content. The metal–insulator transition temperature (T MI ) is observed which decreases with the increase of Ag + content when magnetic field is applied. The resistivity data in high temperature region are explained within the framework of variable range hopping (VRH) and small polaron hopping (SPH) models. The thermoelectric power (S) of the reported samples exhibits a crossover from positive to negative value and value of S increases in doped samples. The analysis of thermoelectric power data confirms that the small polaron hopping model in high temperature region and at low temperature electron–magnon scattering is the dominating in the FM region. With increasing the Ag + content the samples showed very high magneto-resistance (MR%) and temperature coefficient of resistance (TCR%) which make the compound more promising for scientific and technological applications. [ABSTRACT FROM AUTHOR]

At this work, spin- and valley-dependent electron transport through graphene and silicene layers are studied in the presence of Rashba spin- orbit coupling. We find that the transport properties of the related ferromagnetic/normal/ferromagnetic structure depend on the relevant parameters. A fully valley- and spin- polarized current is obtained. As another result, Rashba spin-orbit interaction plays important role in controlling the transmission characteristics. [ABSTRACT FROM AUTHOR]

We report a new fabrication strategy to obtain large area continuous NPGs-on-substrate combining graphene-on-substrate industrial techniques and swift-ion beam irradiation (SHI). Graphene membranes were synthesized on the Cu substrate and afterwards a 600 nm layer of PMMA was spin-coated on the surface to complete the PMMA-Graphene-Cu stack. The PMMA-graphene-Cu trilayer was exposed to a flow of Au heavy ions that penetrate through the entire thickness of both polymer layer and the graphene sheet creating ion-tracks and damages. A consecutive track-etching technique is used with an adequate revealing agent for PMMA, IsoPropyl Alcohol (IPA), to selectively dissolve the latent tracks and damages created during SHI irradiation in the insulating material and the graphene sheet. Resulting from SHI irradiation and track-etching, the graphene nanopores are thus perfectly aligned to the PMMA nanopores, providing, after cupper dissolution, a composite that features both well-defined and truly 2-dimensional nanopores in the graphene layer but that can be handled as a normal polymer film. [ABSTRACT FROM AUTHOR]

We report on magneto-transport experiments in a high-quality sample of highly-oriented pyrolytic graphite (HOPG). Magneto-resistance and Hall resistivity measurements were carried out in magnetic inductions up to B = 9 T applied parallel to the c -axis at fixed temperatures between T =2 K and T =12 K. The sample was submitted to three subsequent irradiations with As ions. The implanted As contents were 2.5, 5 and 10 at% at the maximum of the distribution profile. Experiments were performed after each implantation stage. Shubnikov-de Haas (SdH) oscillations were observed in both the magneto-resistance and Hall-effect measurements. Analyses of these results with fast Fourier transform (FFT) lead to fundamental frequencies and effective masses for electrons and holes that are independent of the implantation fluences. The Hall resistivity at low temperatures shows a sign reversal as a function of the field in all implanted states. We interpret the obtained results with basis on a qualitative model that supposes the existence of an extrinsic hole density associated to the defect structure of our sample. We conclude that the As implantation does not produce a semiconductor-type doping in our HOPG sample. Instead, an increase in the extrinsic hole density is likely to occur as a consequence of disorder induced by implantation. [ABSTRACT FROM AUTHOR]

In intermetallic compounds RE Co 2 Si 2 ( RE =Pr and Nd), cobalt has been partially substituted by vanadium to obtain RE (Co 1− x V x ) 2 Si 2 ( 0 ≤ x ≤ 0.35 ). The parent compounds are antiferromagnetic below about 30 K due to the ordering of localized magnetic moments that are present only on rare-earth ions, cobalt being non-magnetic in the parent compounds. The present study demonstrates that in these compounds where 3 d and 4 f ions occupy different layers in the crystal structure, V substitution and subsequent lattice expansion results in the occurrence of inequivalent magnetic ions and complex interactions that lead to multiple magnetic transitions. At temperatures around 40–50 K, the temperature dependence of magnetization indicates a ferrimagnetic transition which is accompanied by a rapid decrease in the temperature dependence of resistivity. Below temperatures ∼30 K, the samples begin to show ferromagnetic-like behavior with the appearance of a coercive field and saturation in the magnetization at magnetic fields above ∼2 T. These two magnetic transitions are indicated also by prominent λ -like peaks in specific heat measurements. At around 10 K, a sharp drop in the resistivity indicates another magnetic transition which is followed by a rapid increase in coercive field with decrease in temperature. In a magnetic field of 9 T, the latter transition shifts to a lower temperature and that leads to a positive magnetoresistance. The onset of ferromagnetism at ∼30 K is accompanied with an exchange bias field which is observed for the first time in layered intermetallic compounds. The exchange bias field increases rapidly below the transition at ∼10 K and reaches ∼16% of coercive field at 2 K. [ABSTRACT FROM AUTHOR]

In this study, we showed the crystal structure, electric resistivity, Seebeck and Hall coefficients, magneto-resistance, and magnetic susceptibility of Pr 1 − x Ca x Ba 2 Cu 4 O 8 (x = 0.0, 0.02, and 0.05) are all relevant for our understanding of physical properties along CuO double chains. The lattice parameters of Ca substituted PrBa 2 Cu 4 O 8 remained almost invariant up to x = 0.05. Contrary to the Ca doping effect in the PrBa 2 Cu 3 O 7 − δ system, the significant increases in the Seebeck and Hall coefficients due to the Ca substitution indicate a decrease in the carrier number. The significant magneto-resistance effect in the parent sample (16% at 10 K) was significantly reduced down to 5% in the x = 0.05 composition. On the basis of the two types of carrier models, we discussed the influence of Ca substitution on the electrical transport and magneto-transport properties. • Metallic double chain based Pr/Ca124 compounds with low Ca substitution were successfully synthesized by a citrate pyrolysis method. • Despite Ca2+ replacement for Pr3+, the transport and magneto-transport properties of Pr/Ca124 suggested a significant reduction in the carrier number, which is in contrast with the Pr/Ca123 system. • Assuming that a carrier suppression due to the Ca substitution is attributed to the CuO double chains, our overall data for Pr/Ca124 are well explained based on the two-types of carrier transport model. [ABSTRACT FROM AUTHOR]

The composites with composition of (1− x )La 0.67 Sr 0.33 MnO 3 (LSMO)+( x )Ni 0.5 Zn 0.5 Fe 2 O 4 (NZFO) with x =0.0 (S1), 0.04 (S2), 0.07 (S3), 0.10 (S4), 0.30 (S5) and 1.0 (S6) were synthesized by solid-state reaction route. Structural study using Rietveld refinement of X-ray diffraction (XRD) pattern indicates a rhombohedrally-distorted structure (space group R 3 c ) for LSMO phase while to that NZFO compound crystallizes in cubic structure (space group Fd 3 m ). XRD patterns and microstructural analysis show that LSMO and NZFO phase exists independently in Ni 0.5 Zn 0.5 Fe 2 O 4 doped composites. The transport properties of the compositions x =0.0, x =0.04, and x =0.07 showed that NZFO phase improves the resistivity and shifts the metal–insulator transition temperature T MI towards lower temperature. The magnetoresistance (MR) of composite samples with x =0.04 and x =0.07 decreases monotonously from 200 to 300 K in a magnetic field of 8 T. At lower temperatures (~5 K), a sharp drop of negative MR at low fields ( H <1 T) has been observed followed by a slower varying MR at a comparatively high-field regime ( H >1 T) where MR is almost linear with applied magnetic field. Temperature dependence of resistivity for composites samples with x =0.04 and x =0.07 has been best fitted by small Polaron hopping (SPH) and variable range hopping models (VRH). [ABSTRACT FROM AUTHOR]

A number of experiments have been performed to study magnetic, electronic and optical properties of HoNiSi, along with theoretical calculations. The compound crystallizes in orthorhombic crystal structure and orders antiferromagnetically at T N = 4.6 K. Magnetization isotherms show curvature in low fields, revealing a field induced metamagnetic transition. Application of field reduces the resistivity near T N , which results in a large negative MR. The maximum value of MR has been found to be −24% at 4 K for 50 kOe. Strong antiferromagnetic interactions among the moments below 4 K result in positive MR, which changes with field. The antiferromagnetic ordering with the effective magnetic moments of Ho close to the observed value is obtained in the LSDA + U calculations accounting for the electronic correlations in the 4f Ho shell. In the experimental optical conductivity interband transitions involving 4f Ho and 5d Ho forms the main features in good agreement with the theoretical electronic structure of HoNiSi. [ABSTRACT FROM AUTHOR]

In the present work, the structural, magnetic, magneto-transport and thermoelectric properties of polycrystalline compounds of La 0.8− x Bi x Ca 0.2 MnO 3 (0≤ x ≤0.1) compounds are reported. Structure refinement using Rietveld method confirms that the samples are single phased and crystallize in rhombohedral structure with R-3C space group. Magnetic studies reveal that the pristine sample exhibits T C at 221 K and it shift towards lower temperature with Bi doping. Deviation of the temperature dependent of inverse susceptibility curves from the Curie–Weiss law confirms the existence of Griffiths-like phase. All the samples exhibit metal to insulator transition at temperature T MI , which is found to decrease with increase in Bi doping which is consistent with the magnetic studies. Magneto-resistance MR % data shows that its peak value increases with Bi-doping. The analysis of electrical resistivity data in the metallic region ( T < T MI ) suggests that the electron–electron scattering is predominant in this region whereas the insulating region ( T > T MI ) is well described using Small polaron hopping ( SPH ) and Mott's variable range hopping ( VRH ) models. Analysis of thermoelectric power data in the high temperature region suggests that the SPH mechanism is operative in this regime, while the analysis of low temperature data reveals that the electron–magnon scattering is dominant in the region. [ABSTRACT FROM AUTHOR]

For half metallic magnets, spin fluctuation is the same as charge fluctuation. The length scale is controlled by electron–electron interaction and is of the order of the screening length, typically of the order of an Angstrom whereas the ordinary spin diffusion length is of the order of 100 Å or more. We examine the eigenstates for charge and spin transport for systems close to half-metallicity. Due to the electron–electron interaction, the decay length of the eigenstate that corresponds to the longitudinal spin diffusion length is much reduced, consistent with recent experimental results. We explore the consequence of this. We find that there are two parameters that characterize half-metallicity and illustrate our results numerically with a simple model. [ABSTRACT FROM AUTHOR]

A systematic investigation has been carried out on effect of Cr-doping on structural, magneto-resistance, magnetic and thermoelectric power properties of La 0.65 Ca 0.35 Mn 1− x Cr x O 3 compounds. Samples were prepared using conventional solid state reaction method. The XRD analysis using Rietveld refinement reveals that the samples are single phased. Temperature dependent electrical resistivity measurements show the existence of the expected metal–insulator transition ( T MI ) which is followed by a small hump at temperatures lower than T MI . With the application of magnetic field, resistivity of all the samples is found to decrease and T MI is observed to shift towards higher temperature. This is attributed to induced magnetic ordering of the localized t 2g spins and increased electron transfer integral between Mn 3+ /Mn 4+ via oxygen by the application of magnetic field. MR% is observed to increase with the increasing Cr concentration. Magnetic studies show that the Curie temperature, T C and magnetic moment decreases with Cr-content which is consistent with the electrical studies. Electrical resistivity and thermoelectric power data have been analyzed using theoretical models and both suggest that the small polaron hopping (SPH) model is operative in the high temperature insulating region for the entire series of samples. [ABSTRACT FROM AUTHOR]

A systematic study on the structural, electrical, magnetic and thermo-electric properties of La 0.8 Ba x Ca 0.2 − x MnO 3 (0 ⩽ x ⩽ 0.2) manganites is carried out in the present work. The samples have been prepared using solid state reaction technique. All the samples are single phased. It is seen that Ba-doping introduces a structural phase transformation viz. from rhombohedral to cubic system. Electric and magnetic studies respectively show that the metal–insulator transition temperature, T MI and Curie temperature, T C increase with Ba-content. Magneto-resistance (MR) data shows that it decreases with Ba-doping. Analyses of the electrical transport data in metallic region i.e. T < T MI shows that the electrical transport is governed predominantly by electron–electron scattering process. On the other hand, the adiabatic small polaron hopping (ASPH) model is appropriate in the high-temperature insulating range viz. T > T MI . We have used the electrical resistivity data in the entire temperature range (50–300 K) and analyzed using the phenomenological percolation model which is based on the phase segregation mechanism. We have analyzed the Seebeck coefficient data which reveals that the small polaron hopping mechanism is operative in high temperature regime and the low temperature region is examined by taking into account the impurity, electron–magnon scattering, and spin wave fluctuation terms. It is established that the electron–magnon scattering is dominating for the thermoelectric transport below T MI . [ABSTRACT FROM AUTHOR]

Influence of BTO phase on structural and electric properties of LSMO phase has been investigated by synthesizing a manganite matrix-based composite series (1 − x )La 0.67 Sr 0.33 MnO 3 + ( x )BaTiO 3 with x = 0.0, 0.05, 0.10, 0.15, 0.20, and 0.25 (abbreviated as LSMO–BTO) by solid-state reaction method. Rietveld refined X-ray diffraction (XRD) data infers that manganite LSMO compound possess a rhombohedrally-distorted structure (space group R 3 c ), while to that BTO compound crystallizes in tetragonal structure (space group P 4 mm ). The structural parameters and the reliability factors for the LSMO–BTO composite ceramics were successfully determined by the Rietveld refinement. The resistivity measurements infer that the metal–insulator transition temperature was shifted towards lower temperature as well as resistivity increases with increasing BTO content in LSMO–BTO composites. Measurement of resistivity of these samples shows more prominent extrinsic metal insulator (EMI) transition at temperature T EMI . At H = 8 T, the magnetoresistance is enhanced in the wide temperature ranges due to introduction of BaTiO 3 content in La 0.67 Sr 0.33 MnO 3 which could be explained by enhanced spin polarized tunneling. [ABSTRACT FROM AUTHOR]

The carbon-based nanomaterial would push silicon aside and create a post- complementary metal oxide semiconductor world. In this work, we proposed and theoretically investigated an all-carbon spintronic device composed of C 18 cyclo molecule and two zigzag graphene nanoribbon (ZGNR) electrodes with two different sturdy connection modes. It is found that both structures have similar excellent spin-dependent properties. Adjusting the magnetization configuration of two electrodes to be anti-parallel, electrons in different spin states are filtered unidirectionally according to the sign of the applied bias voltage. The molecular junction exhibits a perfect dual spin filtering effect. Moreover, a huge magneto-resistance ratio was found in our propose junctions. The matching of symmetry type of the spin-polarized states in two ZGNR electrodes, as well as the states of C 18 in central region plays an important role in the occurrence of these effects. • All-carbon molecular device based on C 18 cyclo molecule were proposed. • Two types of stable connection models between C 18 cyclo and zigzag graphene nanoribbon electrodes were obtained. • The molecular junction exhibits a perfect dual spin filtering effect. • Present high magneto-resistance ratio over a wide bias voltage. [ABSTRACT FROM AUTHOR]

Highlights: [•] CoFe2O4/SiO2/Co–NiFe2O4 magnetic junction was fabricated using RF/DC sputtering. [•] Spin transport through nanostructure silicon oxide with ferrite as free and pinned layer is our first report. [•] Magnetization studies were done to justify the free layer and pinned layer for our multilayer. [•] Magnetoresistance behavior shows a sharp discriminating between parallel and antiparallel alignment with TMR value of 16%. [Copyright &y& Elsevier]

Abstract: We have studied the magneto-transport of magnetite (Fe3O4) nanoparticles (MNPs) between Au nanogap electrodes (ANGEs) on surface-oxidized Si substrate. The MNP sizes are approximately 40nm and the 100nm thick magnetite thin film (which is formed of the MNP aggregation) was prepared between and around the ANGEs by use of the RF reactive magnetron sputtering method. The distance between the ANGEs and the bridge width of the ANGEs are approximately 50nm and 1.5μm, respectively. The ANGEs were produced by the tilted-angle-deposition method. The optical microscope, scanning electron microscope and atomic force microscope were used to observe the sample surface structure and morphology. To investigate the crystal structure and crystallinity of the MNPs, the X-ray diffraction measurement was performed. The electrical resistance and magneto-resistance ratio of the MNPs between the ANGEs were measured as a function of temperature. The magneto-transport mechanism is discussed on the basis of the spin dependent transport. [Copyright &y& Elsevier]

Abstract: A systematic study of the magneto-resistance (MR), magneto-reactance (MX), and magneto-impedance (MI) effects in single and multiple glass-coated amorphous Co68B15Si10Mn7 microwires is reported. Our studies reveal that the MR, MX, and MI ratios and their corresponding magnetic field sensitivities strongly depend on the number of microwires in an array and on the distance between them. We find that increasing the number of microwires increases the MR and MI ratios and their field sensitivities (ηR and ηZ , respectively) but decreases the MX ratio and its field sensitivity (ηX ). A similar trend is observed for the frequency dependence of these parameters. Increasing the distance between the wires is also found to decrease the MR and MI ratios but increase the MX ratio of the array considerably. From a sensor application perspective, it is interesting to note that for the case of a single microwire, the ηX reaches a value as high as 960%/Oe at a frequency of 1MHz, which is about 192 times of the ηR or ηZ (∼5%/Oe), revealing the possibility of developing ultrahigh sensitivity magnetic field sensors based on the principle of the MX effect. [Copyright &y& Elsevier]

Abstract: 2MeV protons and 1MeV carbon ions are bombarded on highly oriented pyrolytic graphite (HOPG) samples and their electronic transport measurements are carried out in the presence of magnetic field. The Magneto-Resistance (MR) measurements show measurable hysteresis in the resistance value after ion beam irradiation for the in-plane magnetic field direction as well as for the out-of-plane field direction. The MR depends on the thickness of the flake and the method of its separation from the bulk HOPG. The results substantiate that the ferromagnetic coupling between the magnetic moments at the vacancy defect sites in HOPG sensitively depends on the average defect separation. The average defect separation range of 1.7–0.5nm allows only a part of the 40μm thick proton beam irradiated sample to go for ferromagnetic ordering. Similar conclusions are drawn from carbon ion irradiated HOPG flake. The irradiation increases the resistance of the flake as well. [Copyright &y& Elsevier]

Abstract: The perovskite manganite systems have been the materials of tremendous interest due to their strong correlation between structure, transport and magnetism. These materials in their single-crystal form show colossal magneto-resistance (CMR), but the applied fields are very high (∼1–5T). The polycrystalline samples do show high low-field magneto-resistance (LFMR), but good amount of control over particle sizes and grain-boundary distribution is required, which is well known but less realized in practical approaches. In this context, we report on synthesis and manipulation of polycrystalline La0.7Ba0.3MnO3 (LBMO) submicron powders using citric acid chelation. The Citrate-gel route is used to synthesize poly-dispersed LBMO powders which are subjected to citrate chelation for a duration of 0 (LB0) to 4h(LB4) . The samples show improved ordering in X-ray diffraction patterns. Raman spectroscopy scans indicate changed mode signatures due to the probable chelating process, which alters the surface morphology. X-ray photoelectron microscopy shows an evidence of fine citrate layer on the grain boundaries. Low temperature B–H curves exhibit fine hysteresis loops for all samples, while room temperature B–H curves shows paramagnetic response. Scanning electron microscopy images showed the formation of well arranged, connected, mono-dispersed grains of LB4 sample, as against polydispered LB0. The magneto-resistance (at H=100kOe) is seen to enhance for LB4 at its transition temperature (75%, as compared to LB0, where it is 60%), which can be attributed to the well-controlled inter-grain tunneling phenomenon and thin insulating regions in between, created due to citrate chelation, which probably enhances the scattering phenomenon and its susceptibility to applied fields. As citric acid is known to chelate Mn ions, it probably chelates the smaller LB particulate structure and leaves behind citrate-connected submicron grains of LBMO, which are seen to be well engineered. [Copyright &y& Elsevier]

Abstract: The physical properties of Tb3+ ions substitution at A-site are investigated in the layered manganite La1.2Sr1.8Mn2O7. A series of La1.2−x Tb x Sr1.8Mn2O7 (x=0, 0.05, 0.15, and 0.20) shows that doping with a Tb ion of smaller radius in La1.2Sr1.8Mn2O7 caused diffraction peaks to shift to high angle. Some samples have an impure diffraction at about 30°, but all samples form single-phase. Samples can be well indexed on a Sr3Ti2O7-type tetragonal structure with the space group I4/mmm. According to the M-T curves, when x≤0.05, the series of samples shows ferromagnetism at low temperatures. With increasing temperature, they have two magnetic transitions at different temperatures. When x≥0.15, the magnetizations dramatically decrease. The ρ–T curves of samples show the metal–insulator transition for x=0, 0.05, and the maximum MR values in magnetic field 5T are 74% at about 73K and 94% at about 86K. When x≥0.15, the samples remain in the insulator state in the whole observed temperature range, and the maximum MR values of 86% and 69% appeared at 74K and 42K. [Copyright &y& Elsevier]

Abstract: We investigate the electrical transport and magnetic field dependence of nano-patterned La0.7Sr0.3MnO3 devices. We find that the resistivity versus temperature dependence is the same as that observed in thin films, indicating that our nano-patterning preserves the fundamental properties of the material. At temperatures below 20K there is resistivity upturn of ~5 % in the smallest and thinnest device. Structures in a “V” pattern were fabricated in order to investigate domain wall resistance. We find a much smaller resistance area product as compared to previous reports observed in nanoconstrictions and also that the switching field matches that in micromagnetic simulations. [Copyright &y& Elsevier]

Abstract: We investigated electrical- and magneto-resistance control in magnetite (Fe3O4) nanoparticle sinter (MNPS) by the regulation of heat treatment (HT) temperature. MNPS was produced from hematite (α-Fe2O3) nanoparticles (HNP’s) using a deoxidization reaction. The average size of HNP was 30nm, and HT was carried out between 400 and 800°C. X-ray diffraction, magnetization, electrical resistivity (ER), and magneto-resistivity (MR) measurements were performed at temperatures ranging from 5 to 300K. The ER and MR behaviors were considerably different at HT temperatures above and below ∼600°C. After HT below ∼600°C, ER followed the Mott-type variable-range-hopping conduction, and MR showed large values over a wide temperature range. After HT above ∼600°C, ER indicated a Verwey transition near 110K and MR showed small values, except in the vicinity of the Verwey transition temperature. Changing the HT temperature altered the coupling between adjacent magnetite nanoparticles (MNPs) and affected the crystallinity of MNPS. Below ∼600°C, ER and MR were dominated by grain-boundary conduction, while above ∼600°C they were determined by inter-grain conduction. The application of a magnetic field to the grain-boundary region, which had random localized spins, caused a large enhancement in MR. [ABSTRACT FROM AUTHOR]

Abstract: We describe device models for spin injection, transport, and magneto-resistance in structures consisting of an organic semiconductor layer sandwiched between two ferromagnetic contacts. Carrier transport in the organic semiconductor is modeled with spin-dependent transport equations in drift-diffusion approximation. The effectiveness of spin-selective tunnel contacts on spin-polarized injection and magneto-resistance is examined on the basis of a simple analytical model. In agreement with earlier results, we find that spin injection from ferromagnetic metallic contacts into organic semiconductors can be greatly enhanced if (spin-selective) tunneling is the limiting process for carrier injection. We then explore the effects of the injected space charge and of spin relaxation in the semiconductor by comparing the results of a numerical calculation with the analytical model. For relatively thick organic semiconductor layers the injected space charge has strong effects on charge injection and, hence, on spin injection at high bias. Lastly, we consider a simple model for the bias dependence of the tunnel contacts and find that this effect may limit spin injection to relatively low currents. [Copyright &y& Elsevier]

Abstract: The structural magnetic and magneto-transport properties of double perovskite system Ba2− x Sr x FeMoO6 (0⩽x⩽1.0) prepared in bulk polycrystalline form are reported in this paper. X-ray diffraction analysis showed that samples are single phase and the lattice constants decreases with increase in the Sr content. The degree of Fe–Mo ordering has been found decreasing in the series with an increase in the Sr content. Parent compound Ba2FeMoO6 exhibits saturation magnetic moment value of 3.54μB/f.u. at 85K in a magnetic field of 6000Oe. Temperature dependence of resistivity shows metallic behavior for all the samples. The magneto-resistance (MR) of the compound with x=0.4 is higher than that of the other samples. At room temperature this system shows a saturation magnetization value of 1.73μB/f.u. and MR value of 7.08% (1T). The observed variations in the structural and magnetic properties are attributed to the change of chemical pressure due to the substitution of Sr in place of Ba. The effect of antisite disorder (ASD) defects on magneto-transport properties is studied in more detail. [Copyright &y& Elsevier]

Abstract: A series of nano-crystalline Co x Ag100− x solid solutions have been prepared by NaBH4 reduction of the corresponding metal salts at room temperature in Ar gas flow. Alloys heat-treated at 600°C in Ar/H2 (5%) show the evolution of metastable fcc Co precipitates in Ag. Magnetic studies indicate that all the compositions are ferromagnetic with Curie temperatures >400K. For a nominal composition of Co60Ag40, heat-treated at 600°C, an effective negative magneto-resistance (MR) ratio of the order of ∼21% at 350K, at 2T is observed. This could arise from the influence of magnetic field on the electron–phonon scattering effects near to T c and to the spin-mixing scattering by magnons. [Copyright &y& Elsevier]

Abstract: Ferromagnetic shape memory alloy with nominal composition Co37Ni34Al29 is investigated by transport and magnetic measurements. The anomaly due to the martensitic transition is observed around 130–210K. The thermal hysteresis, observed due to martensitic transition in the dc magnetization versus temperature data, gets suppressed at higher applied field. Below 50K, magnetization varies with temperature perfectly as , which signifies that spin wave excitations are largely responsible for thermal demagnetization. The sample shows small negative magneto-resistance, which varies non-monotonically with temperature showing largest value at around 200K. [Copyright &y& Elsevier]

Abstract: We report the results from magnetic, transport and Mo zero field nuclear magnetic resonance measurements on polycrystalline Sr2Fe1− x Al x MoO6. We find that there is a small electron-doping effect induced by Al3+ substitution for Fe, which suggests that Fe is not in the 3+ state assumed in some theoretical models. We show that the decrease in the Curie temperature, T c, with increasing Al concentration can be interpreted in terms of 3D random site dilution. The saturation moment per formula unit, as determined from magnetization measurements, decreases with increasing x but the Mo moment shows a very small increase. The spin-wave dispersion is complicated in this compound and the temperature-dependent Mo moment does not follow the Bloch T 3/2 law. There is no correlation between the resistivity or the magneto-resistance at 77K with the Al concentration, which may be due to different grain boundary properties in each sample. [Copyright &y& Elsevier]

Abstract: We report results from structural, transport and magnetic measurements on polycrystalline Sr2− x Ba x FeMoO6 (, 1 and 2) half-metallic double perovskites. We find a large low field magneto-resistance (MR) of ∼−25% at 0.8T and 77K for samples that have high resistivities. We show that the low field tunneling MR can be modeled by assuming that there is a disordered region near the insulating grain boundaries as proposed by Serrate et al. It is the magnetization from this region rather than the bulk magnetization that determines the MR in polycrystalline samples. [Copyright &y& Elsevier]

Abstract: Pulsed laser deposited thin films of electron doped La0.7Ce0.3MnO3 have been irradiated with 200MeV Ag ions at different fluence values. The irradiation driven alteration on the pink noise (1/f noise), electrical and magneto-transport properties have been investigated. It is observed that the irradiation fluence adjusts the metal–insulator transition temperature, the magnetic field response to the resistance and the noise values. These parameters may assist in tuning these materials for applications. The film irradiated with the lower fluence value of 5×1010 ions/cm2 enhances the performance at room temperature. However, the film irradiated at higher fluence values manipulates these functionalities at lower temperature regime. The normalized noise values in the irradiated films are higher in ferromagnetic regime than in the paramagnetic regime. The observations have been explained on the basis of effects of the presence of swift heavy ion irradiation induced strain and defects. [Copyright &y& Elsevier]

Abstract: The influence of swift heavy ion (SHI) irradiation on electronic transport properties of epitaxial thin films of La0.75Ca0.25MnO3 is studied. The films were irradiated with 250MeV Ag17+ beam at fluence range 1010–1012 ions/cm2. A systematic variation in metal–insulator transition temperature (T p) and peak resistivity have been observed. At low fluence value (3×1010 ions/cm2) the T p is increased by 34K. With the increase in fluence it decreases but remain at upper side up to the fluence value of 3×1011 ions/cm2 as compared to the unirradiated film. The peak resistivity is also decreasing with the increase in fluence up to 3×1011 ions/cm2 and then increases with further increase of fluence. The temperature coefficient resistivity (TCR) is also increased with the fluence. The observed effects are correlated with the effects produced by the applications of hydrostatic pressure. The results are discussed in terms of SHI irradiation induced structural strains in the films. [Copyright &y& Elsevier]

Abstract: Magneto-resistance ratios (MRR) were measured for (Fe3O4)1−x (CrO2) x granular junctions between 77K and 300K, where x is the volume ratio of CrO2 in the measured samples. Since the spin polarization coefficient P of conduction electrons is −1 in Fe3O4 and 1 in CrO2, these junctions are expected to show inverse tunneling magneto-resistance (TMR) effects. In 0.4⩽ x ⩽1, low resistive CrO2/Cr2O3/CrO2 junctions characterized MR behavior, while in x ⩽0.2, high resistive Fe3O4/(γ-Fe2O3 or Fe3O4+δ )/Fe3O4 junctions dominated the magnetic conduction. The inverse TMR effect only appeared at x =0.3 near the percolation threshold x c of CrO2/Cr2O3/CrO2 paths, where CrO2 particles, enclosed by Fe3O4 particles, reached a maximum number. The switching MRR behavior of x =0.3 was very sensitive to the magnetic field. Therefore the present system of (Fe3O4)0.7(CrO2)0.3 has the possibility of realizing a new half metallic spintronics device. [Copyright &y& Elsevier]

The frequency behaviour of the electrical properties of field-aligned CrO2 needle-shape powders has been investigated by the impedance spectroscopy method. The low frequencies R(f) increase with increasing θ, the angles between the applied current direction and the easy axis of the aligned samples. The specific frequency, of which a maximum -X(f) occurred, is varied towards the lower ones as θ increased. Analysis, based on classical electromagnetism as well as equivalent circuit method, has been performed to disclose the mechanism underlying for AC conductivity. [Copyright &y& Elsevier]