Search

In the present communication, ZnO/La0.7Sr0.3MnO3/Al2O3 (ZnO/LSMO/Al2O3) heterostructure was grown using chemical solution deposition (CSD) technique. X–ray diffraction (XRD) measurement confirms the (100) crystallographic oriented growth of LSMO manganite and polycrystalline hexagonal growth of ZnO layer. Temperature dependent resistivity behavior under different applied magnetic fields, performed for two different geometries [current in plane (CIP) and current perpendicular to plane (CPP)], suggests the modifications in metal to insulator transition temperature TP and alterations in resistivity with applied magnetic field and measurement geometry. This also implies the better charge conduction across the ZnO/LSMO interface (CPP) as compared to LSMO film layer (CIP). Various charge conduction mechanisms have been employed to understand the charge transport for observed low temperature resistivity minimum, metallic behavior, insulating state and magnetoresistance (MR) of LSMO film and ZnO/LSMO interface. Electroresistance (ER) and field effect configuration (FEC) have been investigated across the ZnO/LSMO interface by recording the LSMO channel resistance, at room temperature, that suggest the tuning of signature and value of ER by considering forward and reverse bias modes across the interface. FEC studies show the large ER ∼ +750% and −85% across the LSMO channel with its tunability under different interface biases.

Here, we report the synthesis and characterization of the Nb2Pd(S0.9Te0.1)5 superconductor. The resultant polycrystalline sample is consists of solid chunks along with mesh of fibers which are grown in thin long rod shapes having length in several millimeters with cross-sectional area around 5x3 µm2. The normal state of this superconductor behaves abnormally compared to its parent compound (Nb2PdS5) which is shown here. In high temperature regime (T > 125K) it follows the power law which is completely different from its parent analog which shows metallicity (linear behavior) in high temperature range. Below this temperature region a broad peak appears centered around T* ≈ 62K, the origin of this anomaly is unknown right now, followed by a dip which is centered around T’ ≈ 23K which may be some sort of electron localization or some gap like excitation which preceding the superconducting transition having onset at Tc (onset)≈ 6.7K. The upper critical field value Hc2(0) = 52.24T enhances in these superconducting fibers. Aslamazov-Larkin (AL) theory shows three significant (3D, 1D and short-wave (SW)) fluctuation regimes in these superconducting fibers.

In the present communication, (1–x) La0.7Ca0.3MnO3 (LCMO) + (x) ZnO (x = 0, 0.10, 0.20) nanocomposites were synthesized by sol–gel method and studied for their charge carrier transport properties. The result of X–ray diffraction (XRD) confirms mixed phases of orthorhombic LCMO with hexagonal ZnO. ZnO admixing does not show any significant change in lattice parameters of LCMO however the peak intensity and crystallinity get suppressed with increase in ZnO content. The samples have been characterized for their electrical transport behaviors using four probe resistivity measurements which confirm that all the studied samples exhibit characteristic insulator to metal transition at temperature TP that decreases with increase in ZnO content. There is a discrepancy in the resistivity values between the LCMO: ZnO nanocomposite samples having the ZnO contents x = 0.10 and 0.20. Variations in the charge carrier transport parameters (i.e. resistivity and TP) with ZnO content have been attributed to the magnetic interactions between manganite and ZnO phases and phase separation scenario in LCMO manganite phase. Various models and mechanisms have been employed to understand the charge conduction processes across the lattices of studied nanocomposites. The largest magnetoresistance (MR) has been seen for x = 0.20 in the LCMO: ZnO nanocomposite which has been attributed to the different distribution possibilities of ZnO within the LCMO manganite lattice of the nanocomposite samples.

A comprehensive study of superconducting and normal state properties of Nb2Pd(S0.9Te0.1)5 system which consists of solid chunks embedded with mesh of fibers has been presented here. Below the superconducting transition temperature, in different iso-magnetic fields, the motion of vortices in mixed state has been analyzed using thermally activated flux flow (TAFF) model and the obtained thermal activation energy (TAE) follows Kramer’s scaling which suggests the dominance of mechanism similar to grain boundary pinning in these fibers. Bulk nature of superconductivity is clearly seen in specific heat data, however with a jump of ∼0.97, less than the BCS estimate, places these fibers in weak coupling strength limit. Low temperature electronic heat capacity down to 2 ​K point towards a fully gapped s-wave superconductivity in these fibers. Moreover, normal state study using thermoelectric power data suggests a hole dominated transport in this system.

In this report, ZnO /La0.3Ca0.7MnO3 /SrTiO3 (ZnO /LCMO /STO) heterostructures, with various thicknesses of LCMO, were grown successfully using chemical solution deposition (CSD) method. X–ray diffraction (XRD) measurement confirms the presence of LCMO and ZnO phases only without any other unwanted phases. To understand the charge conduction mechanisms across ZnO /LCMO interface as well as for LCMO manganite thin layer, temperature dependent resistivity measurements have been investigated under different applied magnetic fields. The measured ρ (T) data of all the heterostructures in current perpendicular to plane (CPP; for ZnO /LCMO interface studies) mode and current in plane (CIP; for LCMO thin layer studies) mode show the semiconducting behaviour throughout the temperature and magnetic field range studied. The semiconducting state of all the heterostructures have been studied using Mott type variable range hopping (VRH) mechanism to understand the field dependence of charge carrier localization length. Observed negative magnetoresistance (MR) has been discussed in detail with its dependence on applied magnetic field, temperature and manganite layer thickness.

Nanocomposites consist of ZnO and La0.3Ca0.7MnO3 (LCMO) nanoparticles, prepared by cost effective sol–gel method, have been studied for their transport and magnetoresistance (MR) behaviors. Different ZnO nanoparticles contents (weight ratio) were mixed with LCMO nanostructured manganite to understand the possible interactions between ZnO and LCMO nanoparticles. X–ray diffraction (XRD) measurement was performed for all composites and structural quality was verified by performing Rietveld refinements. Variation in an average crystallite size for LCMO and ZnO nanoparticles in different composites has been discussed. Temperature dependent resistivity measurements under different applied magnetic fields suggest the semiconducting nature of all nanocomposites under all applied magnetic fields. Mott type variable range hopping (VRH) mechanism has been employed to understand the dependence of charge carrier localization in LCMO nanostructured manganite lattice on the applied magnetic field and ZnO nanoparticles content within the nanocomposites. Observed MR behavior has been understood under the influence of temperature and ZnO nanoparticles content in the context of spin polarized tunneling (SPT) and magnetic field induced improved conduction across the manganite lattice. Grain and grain boundary contributions to the MR behavior have been explained by using theoretical model fits to obtained MR data at different temperatures for all studied LCMO:ZnO nanocomposites. Magnetic nature of studied LCMO:ZnO nanocomposites has been understood by performing zero field cooled (ZFC) and field cooled (FC) measurement protocols based magnetization and magnetic isotherms measurements that confirm the coexisting magnetic phase in all studied nanocomposites. Magnetic nature has been understood on the basis of weakening of zener double exchange (ZDE) mechanism within the magnetic lattice of LCMO manganite and magnetic contribution from the free charge carriers within the ZnO clusters.

In this communication, structural, microstructural, transport and magnetotransport properties are reported for La0.7Pb0.3MnO3/LaAlO3 (LPMO/LAO) manganite films having different thicknesses. All the films were irradiated with 200 MeV Ag+15 swift heavy ions (SHI). Films were grown using the sol-gel method by employing the acetate precursor route. Structural measurements were carried out using the X-ray diffraction (XRD) method at room temperature, while atomic force microscopy (AFM) was performed for the surface morphology. Temperature dependent resistivity under different applied magnetic fields for all the films shows metal to insulator transition at temperature TP. In addition to the metal to insulator transition at TP, the films also exhibit low temperature resistivity upturn behavior. Resistivity, TP and upturn behavior are highly influenced by the film thickness, applied magnetic field and irradiation. To understand the nature of charge transport for the low temperature resistivity behavior and metallic and insulating (semiconducting) regions, various models and mechanisms have been verified and the most suitable mechanism has been found for each region in the resistivity curves. Magnetoresistance (MR) is affected by temperature, film thickness and irradiation. MR behavior has been understood in terms of combined and separate contributions from grains and grain boundaries in the films.

One of the serious causes for materials failure is Wear. It affects the reliability and lifetime of material leading to a number of economic losses. The containers used for the storage of bulk solids are usually called Bins, Bunkers, Silos or Tanks. Wearing of metal is one of major problems that occur during material discharge from silos. To minimize damage of metal, liners are used which are replaceable and prevents the equipment from material wear out. Generally Stainless Steel 304 is being used as liner material for bunkers because of its high strength, high corrosion resistance and high toughness. In this paper we have considered UHMWPE and Cast Nylon as Liner materials because of their high toughness, good wear resistance and low coefficient of friction. The main objective of this paper is to evaluate the wear rate on different liner materials like SS 304, Mild Steel, UHMWPE, and Cast Nylon using dry abrasion tester by varying Load and Speed.

We have reported in this work the study of correlation between electrical transport and magnetic properties of La 0.5 Ca 0.5 Mn 0.98 Bi 0.02 O 3 polycrystalline sample prepared by solid state method. Structural analysis reveals that presently studied compound crystallizes in the orthorhombic structure with Pnma space group. Temperature dependence of magnetization indicates that our studied compound undergoes a paramagnetic–ferromagnetic transition at Curie temperature T C =237 K. Magnetotransport analysis was successfully carried out using percolation model in the temperature range 40–300 K for magnetic field values up to 14 T. Strong correlation between electrical and magnetic properties was observed along with the absence of charge ordering inside the structure of our sample.

Heat capacity studies on the Kondo lattice system Ce(Ni1−x Cu x )2Al3, in the presence of magnetic fields, were reported for x = 0.0−0.4. The physical properties of the intermediate compositions like x = 0.3 and 0.4 were known for their enhanced thermoelectric power and hence have been analysed with an extra interest. It was also shown from the X-ray diffraction that these systems with x = 0.3 and 0.4 were in single phase in terms of sample purity and it stabilized the phases easily with the increase in the Cu doping in the system. The low temperature rise in C p/T below 10 K under the influence of high magnetic fields was analysed using a multi-level Schottky effect. A gradual decrease of the total angular momentum (J) with the increase of applied magnetic fields indicated a scenario of screening of Ce3+ magnetic moment while simultaneously the system settled for the Fermi liquid state. The screening thus seen was in line with the expectations of electrical conductivity measurements on these samples.

Metal to Insulator Transition (MIT) in a new series of polycrystalline samples of Cr doped FeSi is reported. X-ray diffraction, resistivity, thermopower and heat capacity measurements are carried out on Fe1-xCrxSi for Cr concentration x = 0.0–0.15. The critical concentration (xc) for MIT from resistivity is observed as xc = 0.0194 ± 0.005. The magnitude of maximum value of the thermopower and Sommerfeld coefficient show significant deviation near x = 0.02 unanimously agrees well with that of the xc obtained from the resistivity measurements. It is revealed that electronic states of Cr form an impurity band in between the valence and conduction bands for x > xc. From two parallel resister model fit to both the resistivity and thermopower measurements we have shown that low temperature metallic behavior is due to impurity conduction band and high temperature semiconducting behavior is due to excitation of the charge carriers from semiconducting bands.

Background: Hemorrhoidal disease is a painful concern to the sufferer and the treating surgeon. Several methods are available for treatment of hemorrhoids. Milligan Morgan hemorrhoidectomy is the most widely practiced Gold standard surgical technique for the management of 3 rd and 4 th degree hemorrhoids. Staplers are novel methods known for its simplicity, ease and standardization to an anastomosis. Methods: A prospective randomized control study was done including 60 consecutive patients. The patients were divided into two groups viz. Stapler hemorrhoidectomy group (SH) and Open (Milligan Morgan) hemorrhoidectomy group (OH). Randomization of the patient and assigning them to either of the group was done by the sealed envelope technique on the morning of the surgery. Pain score data sheet was filled out by the patients postoperatively. Data was analysed using SPSS. Significant difference was estimated using Chi Square test and Student’s ‘t’ independent test. Level of significance was taken as 0.05. Results: Sixty patients in two equal groups were studied. Mean age of the two groups was similar. The male: female ratio was 6.5:1 for the stapled group and 9:1 for the open group. The mean operating time for open group was significantly higher than the stapled group (P = 0.0001). The SH group returned to normal activity significantly early. There was no significant difference in pain score on day one. Pain score was significantly lower for the SH group on days 2 and 3. There was no significant difference in complication between the two groups. Conclusions: Operative time, duration of hospital stay and return to normal activity were satisfactory with stapler hemorrhoidectomy than the open method. Hence those who can afford the cost of surgery will definitely benefit, though it cannot be prescribed to all patients due to economic constraints. We still suggest long-term follow-up of all stapler hemorrhoidectomy patients.

Nb2PdS5 is a novel superconductor having promising potential for applications. Synthesis of this by solid state reaction, characterization using susceptibility and resistivity of Ta substituted Nb2PdS5 is reported in the present paper. Nb1.75Ta0.25PdS5 shows a diamagnetic transition at 6K while the onset of superconducting transition in resistivity is found at 6.73K; the slight difference is attributed to Aslamazov-Larkin paraconductivity fluctuations. This can be ascertained from the fact that the transition seen in resistivity is so broad that the zero resistance state is elusive due to weak inter grain coupling. We also report temperature dependence of resistivity under magnetic fields up to 16T that shows considerable broadening in fields that can be attributed to the field induced resistive state with underlying vortex motion. The results are explained based on models like thermally activated flux flow (TAFF) in the light of Kramer’s relation. The normal state just above Tc has a negative temperature co-efficient of resistivity reminiscent of the Anderson localization scenario. The estimated critical field of 27T is more than two times higher than that of Pauli limit.

Magnetic, resistive, and magnetoresistance measurements were used to investigate the percolative nature of A-site disordered La0.75Ca0.25−xSrxMnO3(x = 0, 0.10) manganites. La0.75Ca0.15Sr0.10MnO3 has an orthorhombic structure and second order magnetic phase transition indicates the presence of two prominent downturns T* and Tferro above the Curie temperature (TC) in the derivative of the inverse susceptibility measurements. These observations are in agreement with the percolation model and the results are discussed in the light of phase separation happening in small polarons present in the insulating phase.

Electrical resistivity and magnetoresistive behaviour of bismuth-substituted lanthanum manganites La0.4Bi0.1Ca0.5−x Sr x MnO3 (x = 0.1 and 0.2) were systematically studied by varying the temperature from 2 to 300 K and the magnetic field up to 12 T. The samples were found to crystallize in rhombohedral structure and their morphology shows near-spherical nanosize crystallites. Charge ordering was observed in both the samples under zero field conditions and corresponding transition temperature T CO was found to decrease with the increase of x. Resistivity measurements with magnetic field also showed suppression of magnetoresistivity (MR) with the increase of x and the maximum MR was found to be 98 and 93% for x = 0.1 and 0.2, respectively, at 10 T. In the high-temperature domain, the electronic transport was observed to be dominated by the variable range hopping mechanism for both the samples, whereas in the low-temperature domain the electrical conduction of x = 0.1 sample was observed to be contributed by various other electron scattering mechanisms.

CeNi2Al3 system is a potential candidate for low temperature thermoelectrics. Substitution studies, especially at the Ni site are considered to be of importance due to the drastic tuning of its physical properties. Resistivity in magnetic fields and thermoelectric power measurements of Cu doped CeNi2Al3 (x=0.0 to 0.4) system is reported in this investigation. This dense Kondo lattice system is investigated with an aim of understanding its basic transport mechanism. Negative magnetoresistance is seen for x=0.3 and 0.4 in the magnetic field up to 14 T. Deviation from the Kondo behavior occurs at temperatures close to 2 K with a down turn in resistivity. The nature of resistivity at low temperatures is investigated in view of the possible evidence for Fermi liquid behavior and also the formation of heavy Fermion in corroboration with specific heat studies. Doping dependence of linear diffusion coefficient and Sommerfeld coefficient of specific heat are analyzed and discussed in connection with the heavy Fermion formation. The results obtained show a promising trend in tuning these materials by way of Kondo route as well as by the substitution especially at the Ni site in the present system. Copyright © 2015 VBRI Press.

We have reported in this work the effect of the partial substitution of lanthanum by samarium on the structural, electrical and magnetic properties of La 0.5 Ca 0.5 MnO 3 . The magnetic study indicated that substitution promotes charge ordering and weakens ferromagnetism. Below T C =123 K, the compound La 0.4 Sm 0.1 Ca 0.5 MnO 3 is a mixture of ferromagnetic and charge ordered antiferromagnetic domains. Between T C and T CO =215 K, the structure is paramagnetic with the presence of antiferromagnetic domains. The fractions of the coexisting magnetic phases are highly dependent on the applied magnetic field value. Resistivity measurements reveal the presence of an insulating-metal transition at T ρ =123 K. The equality between T C and T ρ indicates the presence of a correlation between magnetization and resistivity. For only 1 T applied field, we have reported a colossal value of magnetoresistance reaching 73% around T C . The origin of this high value is attributed to phase separation phenomenon.

Correction for 'Charge transport mechanisms in sol-gel grown La

In this communication, structural, microstructural, transport and magnetotransport properties are reported for La

The thermoelectric power (TEP), resistivity, and heat capacity of the polycrystalline Ce(Ni1−xCux)2Al3 system, for x = 0.0–0.4, are reported. A clear enhancement of TEP at low temperatures is seen upon substitution of Cu and is expected to be useful for low-temperature thermoelectric applications. To understand such an enhanced TEP we have employed a two-band model based on the Ce-4f and conduction bands proposed by Gottwick et al. A clear evolution of a 4f band moving toward the Fermi level that is becoming sharpened is seen and is predicted to be close to resonance. The fit parameters of the TEP (S) are physically reasonable. The resistivity data shows an evolution from a simple compensated metal to a paramagnetic one via the Kondo route. This is in line with TEP parameters. In addition, a clear enhancement seen in the electronic part of the heat capacity upon Cu substitution and the evolution of magnetoresistance behavior corroborates the results. Possible bipolar effects are also taken into consideration along with an electron–phonon interaction term to explain the almost temperature-independent part of the resistivity, still yielding a considerable component of disorder.

The superconducting transition temperature of niobium silicon oxynitride (Nb0.87Si0.09□0.04)(N0.87O0.13) exhibits a gradual reduction from 16.8 K to around 11 K under an increasing applied magnetic field of up to 14 T. This relatively small Tc reduction under an applied magnetic field suggests a robustness of its superconducting behavior in comparison to that in the parent niobium oxynitride. It was similar to the flux pinning effect observed in the large magnetic hysteresis of the niobium-silicon oxynitrides in our previous study. Both Si K-edge XANES and 29Si MAS-NMR indicated that the local structure of pinning centers around the silicon atoms close to cationic vacancies was similar to that of Si in amorphous SiO2 in the rock-salt structure of niobium oxynitride.

We report here the results of transport and dc magnetization studies of Ga-doped Ni2Mn1.32In0.68 (Ni2Mn1.32In0.68−xGax, x = 0, 0.04, 0.08, 0.16, 0.20, and 0.28) alloys. The parent sample (x = 0) does not show any structural instability, however small Ga substitution at the In site (x = 0.08) suddenly induces martensitic transition in it. The studied alloys are all found to be ferromagnetic below about room temperature and the martensitic transition temperatures are found to be in the range between 175 K and 240 K depending upon x. Samples showing thermally driven maretnsitic transition ( x ≥ 0.08) are also found to be susceptible to the applied magnetic field, and both magnetization and magnetoresistance indicate the signature of field-induced transition. Upon cooling under a magnetic field, we observe kinetically arrested state which is particularly prominent in low Ga containing samples (x = 0.08, 0.16). It clearly demonstrate that these Ga doped samples posses all the properties of metamagnetic shape memory alloys. We argue that the magnetically arrested state in the alloys is closely connected to the competition between chemical and magnetic free energies associated with the martensitic and austenitic phases.

Owing to the higher magnetic transition temperature (TC), above RT and large magnetoresistance (MR) exhibited by La0.7Pb0.3MnO3 (LPMO) manganite, we have carried out the studies on the effect of 200 MeV Ag+15 ion irradiation on LPMO films. It is interesting to note that, the modifications in the surface grain morphology and roughness in higher thickness (>200 nm) LPMO films, due to irradiation, affects the transport and magnetotransport, in a prominent manner, which has been understood in the light of enhancement in the scattering of charge carriers. The results of the structural, microstructural, transport and magnetotransport properties of pristine and irradiated LPMO films (150–350 nm) have been discussed in this communication.

In this communication, we investigate the thermoelectric properties of a charge density wave material TiSe2 upon Cu intercalation. Polycrystalline Cu x TiSe2 (x=0–0.11) alloys were synthesized using solid state sintering process and their morphological and structural properties were investigated. The material grows in layered morphology and the c-lattice parameter increases linearly with x. The temperature dependent resistivity measured in the 300–5 K range, shows that increasing x leads to a systematic transition from charge density wave state to the metallic state. For x=0.11, the room temperature thermoelectric figure-of-merit is found to be 0.104, which is higher by seven orders in magnitude (i.e. 1.93×10−8) measured for pristine TiSe2 and comparable to the other reported thermoelectric materials. These results show that Cu x TiSe2 are a potential material for the low temperature thermoelectric applications.

Unusual magnetoresistance observed in weak itinerant ferromagnetic metal Fe0.9Co0.1Si is addressed. We invoke localization effects significantly contributing to the positive magnetoresistance apart from quantum interference effects (QIE), a new mechanism for magnetoresistance at low temperatures. QIE are dominant only at very low temperatures while localization effects are progressive out of the sub-Kelvin domain. Dominance of localization effects in Kelvin range with increasing applied magnetic field is demonstrated. An unconventional effect of magnetic field on resistivity, favors a least dominant role of ferromagnetic correlations. The H–T phase diagram explore the regions of H3/2 (paramagnetic region) and QIE (Δσ ∝ H1/2) and its extension into the paramagnetic region. A new region of linear field dependence of MC (Δσ ∝ H) is also found and reported. Qualitative analysis of thermopower and its correspondence with electrical resistivity strengthens the concept that the same electrons are responsible for both electrical and magnetic properties. It is also reported that the onset of magnetic and QIE effects is well above TC.

Niobium compounds continue to be an interesting family of superconductors, with the recent addition of oxynitrides to it, which can be categorized as low-Tc superconductors (LTS) because they exhibit superconductivity below Tc∼17 K. In this paper, we report the superconducting properties of three members of the family of niobium oxynitrides, viz. (Nb0.89Al0.11)(N0.84O0.16), (Nb0.95Mg0.05)(N0.92O0.08) and (Nb0.87Si0.09□0.04)(N0.87O0.13). Low temperature dc and ac magnetization measurements have been performed. In addition, heat capacity has been recorded at low temperature under applied magnetic fields. A detailed analysis of the data is presented.

Both Ba4Mn3O10 and Sr4Mn3O10 crystallize in an orthorhombic crystal structure consisting of corrugated layers containing Mn3O12 polydedra. The thermal variation of magnetic susceptibility of the compositions consists of a broad hump like feature indicating the presence of low dimensional magnetic correlation. We have systematically investigated the magnetic data of these compounds and found that the experimental results match quite well with the two dimensional Heisenberg model of spin-spin interaction. The two dimensional nature of the magnetic spin-spin interaction is supported by the low temperature heat capacity data of Ba4Mn3O10. Interestingly, both the samples show dielectric anomaly near the magnetic ordering temperature indicating multiferroic behavior.

CeNi2Al3 system has evolved in to a known thermoelectric material with a usable figure of merit at low temperatures. Kondo effect plays a crucial role in the enhancement of TEP in this system especially when the Ni site is substituted with non-magnetic elements like Cu. Effect of high magnetic fields on various properties of this system is yet to be explored. Ce(Ni0.7Cu0.3)2Al3 is a representative sample that has a significant enhancement of TEP whose reasons are being explored recently. Here we report the magnetoresistivity measurements on this sample down to 2K and fields upto 14T. The famous negative ln(T) rise with a minimum at 14.5 K is getting suppressed by the magnetic fields. Magnetic correlations are observed with increasing magnetic field strength in the form of a hump like behavior due to competition between Kondo and RKKY interactions. This hump is shifted to higher temperatures with increase in the field strength which indicates probable onset of ferromagnetic correlations that is being corro...

Nearly exponentially decaying heat capacity was observed exceptionally in a well-characterized naturally assembled hexagonal closed packed lattice of 4.0 nm nickel nanoparticles (NPs). It was also associated with quantum jumps. These were however not observed in other NP sizes and have negligible effects of high magnetic fields. Magnetic susceptibilities in contrast revealed the evolution of quantum size effects with a decrease in particle size. They exhibited sharp rise below about 30 K and vestiges of saturations below 5 K. The sharp rise was explained by Curie-like characteristics of odd electrons, while the saturations tend towards the orthogonal even-like case.

Correction for ‘Charge transport mechanisms in sol–gel grown La0.7Pb0.3MnO3/LaAlO3 manganite films’ by Eesh Vaghela et al., Phys. Chem. Chem. Phys., 2017, DOI: 10.1039/c6cp07730g.

The ground-state magnetic properties of hexagonal equiatomic alloy of nominal composition Mn_{0.8}Fe_{0.2}NiGe were investigated through dc magnetization and heat capacity measurements. The alloy undergoes first order martensitic transition below 140 K with simultaneous development of long range ferromagnetic ordering from the high temperature paramagnetic phase. The undoped compound MnNiGe has an antiferromagnetic ground state and it shows martensitic like structural instability well above room temperature. Fe doping at the Mn site not only brings down the martensitic transition temperature, it also induces ferromagnetism in the sample. Our study brings out two important aspects regarding the sample, namley (i) the observation of exchange bias at low temperature, and (ii) spin glass like ground state which prevails below the martensitic and magnetic transition points. In addition to the observed usual relaxation behavior the spin glass state is confirmed by zero field cooled memory experiment, thereby indicating cooperative freezing of spin and/or spin clusters rather than uncorrelated dynamics of superparamagnetic like spin clusters. We believe that doping disorder can give rise to some islands of antiferromagnetic clusters in the otherwise ferromagnetic background which can produce interfacial frustration and exchange pinning responsible for spin glass and exchange bias effect. A comparison is made with doped rare-earth manganites where similar phase separation can lead to glassy ground state., Accepted for Publication in Europhysics Letters

We report the results of temperature dependent magnetotransport measurements on PLD grown GdBa2Cu3OZ (Gd-123) film in the superconducting transition region, TC0 < T < TConset. It is observed that, on application of magnetic field (0 – 14T), TConset (temperature at which superconducting transition starts) remains unchanged while TC0 (temperature at which resistance becomes zero) gets suppressed with field, resulting in the increase in superconducting transition width (ΔTC). Effect of applied field on the flux dynamics, in superconducting transition region, has been understood in the light of thermally activated flux flow (TAFF) model and variation in pinning energy (U0) in Gd-123.

Electrical resistivity and heat capacity measurements on Cerium based dense Kondo compound Ce3Al have been reported. Clear signatures of first order structural transition at 108K, followed by a Kondo minimum and coherence are clearly seen in resistivity. The structural transition is robust and is not affected by magnetic fields. Heat capacity measurements reveal an anomalous enhancement in the heavy fermion character upon magnetic fields. Vollhardt invariance in specific heat C(T.H) curves have been observed at T=3.7K and at H ≈ 6T.

We report electrical resistivity of Ce2.1Nd0.9Al compound under applied magnetic fields. Magnetic field effect on the structural transition and Kondo ordering is studied. 30% Nd doping in Ce3Al makes TS = TK∼25K. Resistivity fits at low temperatures at different magnetic fields reveal a clear competition between Kondo and e-e interactions. It is demonstrated that Kondo interactions are weakened by the applied magnetic field and thus enhancing the e-e interaction. There seems a characteristic field where both the interactions contribute equally and for this sample it is around 6T.

We study, experimentally, the zero field temperature dependence of electrical resistance and Seebeck coefficient in B20 cubic type structure Fe0.8Co0.2Si. Ferromagnetic and metal like to semiconductor like transition temperatures are determined to be 32K and 70K, respectively and electron type charge carriers contributed to the Seebeck coefficient largely and resulted in negative sign. The gradual upturn in thermopower at low temperatures is attributed to change in electronic structure due course of magnetic transition from spin unpolarized to polarized state.

Here, we explore magneto-transport properties on 3d transition monosilicide MnSi. Zero field resistance as a function of temperature for MnSi shows a drop at the onset of magnetic ordering. A strong negative magnetoresistance can be explained as the suppression of spin fluctuations and magnetic field tuning of scattering strength of conduction electrons. MnSi is useful for technological application as it shows an appreciable percentage of magnetoresistance value of 12 to 20 even at moderate fields of 2-5T, respectively.

We report here induction of superconductivity by doping Copper (Cu) in the well known CDW conductor, TiSe2. Resistivity of parent TiSe2 and Cu0.08TiSe2 were measured down to 1.8K and fields upto 14T. The CDW transition in the parent compound TiSe2 is around 150K, as signaled by a huge but broad hump in the resistivity. Upon introduction of Cu in the TiSe2 matrix, superconductivity is observed. The zero field Tc is 2.92K, is quite interesting and comparable to that of literature. Various superconducting parameters are estimated and discussed.

Here, we report heat capacity and magnetocaloric effect (MCE) on R5T4 ternany compound Dy5Ge3Si. Heat capacity depicts a peak at 48.4 K which is associated with antiferromagnetic ordering. It gets suppressed and shifts towards low temperatures with field. The estimated critical field is 5 T for antiferro to ferromagnetic transition. Heat capacity plays a significant role in determining MCE, where from isothermal entropy change and adiabatic temperature change can be derived. From MCE point of view, sample shows maximum ΔS of 6.6 mJ/g‐K at 56.5 K and relative cooling power (RCP) of 356.4 J/kg for temperature range from 46–100 K and hence can be used for magnetic cooling technological applications.

Anomalously large RCP (Relative Cooling Power) and a reasonable high adiabatic change ‘ΔT’ has been observed in magnetocaloric composite sample Dy5Si4 : Dy5Si3 for a nominal ratio of 2:1. Observed magnetic ordering temperatures for such a composite is 136 K and 39 K respectively which can be assigned to its constituents. Even though the observed ‘ΔT’ is only 5 K for a field of 14 T, the combined RCP is very large, viz 1283 J/kg. Added merit is the width of temperature over which cooling can be done is 95 K. This makes the system more promising and may be a possible candidate for the Ericsson cycle over a temperature range from 140–35 K.

Skutterudites is known to have fascinating ground states depending upon the void filling. Heat capacity of partially filled Pr0.8Pt4Ge12 and doubly filled Pr0.8Nd0.2Pt4Ge12 skutterudites has been investigated. Superconducting gaps have been quantified through heat capacity in the presence of magnetic fields. C/T versus T2 plot of Pr0.8Nd0.2Pt4Ge12 shows an upturn at low temperatures and this tendency increases with magnetic field, suggesting the possibility of a field induced NFL like states due to magnetic correlations co‐existing with superconductivity.