Dc Resistivity Measurements Research Articles

Composition dependence of structural, magnetic and electrical properties of Co substituted magnesium ferrite

In this work cobalt substituted magnesium spinel ferrite having general formula Mg1-xCoxFe2O4 (where x = 0.0, 0.1, 0.15,0.2,0.25 and 0.3) was synthesized by solid state reaction method. All the sample are characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Vibrating sample magnetometer (VSM) and dc resistivity measurements. XRD analysis confirms the formation of single phase spinel and the calculated lattice constant ‘aexp’ from XRD decreases as substitution of Co (x) is increased. The FTIR spectra reveled two prominent frequency bands in the wave number range 400–600 cm−1, which confirm the cubic spinel structure. Magnetic studies revealed that the saturation magnetization attains a maximum value when x = 0.2, and then decreases for higher concentration of (x). This non-linear trend in magnetization has been explained on the basis of redistribution of magnetic and non-magnetic cations among A and B sites of the spinel lattice. A significant influence of cation distribution observed on DC electrical resistivity and activation energy.

Investigation of magnetic and transport properties of La0.8Sm0.2O0.5F0.5BiS2 superconductor under external hydrostatic pressure

The dc electrical resistivity and magnetization measurements as a function of temperature 1.8-300 K were formed at external hydrostatic pressures on normal and superconducting state of new polycrystalline BiS2 based layered La0.2Sm0.8BiS2O00.5F0.5 superconductor. In situ, electrical resistivity measurements, At ambient pressure the superconducting transition temperature (Tc) at ~3 K which are enhanced substantially under external pressure to 10.3 K at 1.74 GPa with positive pressure coefficient, dTc/dP= 4.19 K/GPa. Further increasing pressure Tc has been decreased upto 6.2 K at 1.96 GPa with negative pressure coefficient dTc/dP= -2.09 K/GPa. From the normal state resistivity exhibits the strong suppression of the semiconducting behavior in La/SmO0.5F0.5BiS2 compounds suggests that the Fermi surface is in the vicinity of some instability. We report here the enhancement of Tc from 2.83 to 5.86 K with small increase in pressure upto 0.8 GPa with similar pressure coefficient of dTc/dP= 3.78 K/GPa. However, it should be noted that either chemical substitution or physical pressure on these systems show a dome shaped Tc variation which means that the enhancement may not be achieved for higher doping concentration and (or) pressure s beyond an optimum level. In our results, exhibits which higher Tc may be achieved lies around 1.74 GPa. Above this pressure the Tc may decrease and exhibit a dome shaped behavior similar to other rare –earth systems of BiS2 and Fe-based superconductors. Substantial enhancement of superconductivity under moderate pressure in studied new BiS2 based superconductors call for the attention of condensed matter physics community.

Experimental Assessment of Microwave Loss Caused by Non-Hexavalent Chromium-Based Conversion Coatings

Abstract Conversion coatings are used to inhibit corrosion on aluminum structures while maintaining electrical conductivity. The most common type of conversion coatings in aerospace applications (MIL-DTL-5541 Type I), contain hexavalent chromium compounds as the corrosion-inhibiting additive. These Type I conversion coatings have a long pedigree and are highly effective in preventing corrosion; however, the hexavalent chromium compounds in these coatings are carcinogenic and water-soluble. Therefore, the use of these compounds is highly regulated in order to protect both workers and the public leading to high cost in both use and disposal. In addition to these regulations, use of these materials on new designs for DOD is prohibited by DFARS 48 CFR Parts 223 and 252, and is scheduled to be prohibited in Europe in September 2017 by REACH regulations. In response, new more environmentally friendly non-hexavalent chromium-based processes are becoming available. Coatings resulting from these types of processes are referred to as MIL-DTL-5541 Type II conversion coatings. The long term reliability and performance impacts resulting from the use of these coatings are not fully understood and there currently is an effort in the aerospace industry organized by NASA to fully define these impacts while hardware is still in the design stage. While significant work has been performed to define the corrosion performance of various type-II conversion coatings, there has been minimal work performed to quantify the impact a type-II conversion coating would have on RF electrical assemblies. Of particular interest is the impact a conversion coating can have on microwave loss at higher frequencies. Many RF electrical assemblies use aluminum radiator and waveguide structures to transfer energy between components and radiate into freespace. If microwave losses increase due to a change in conversion coating, there could be negative impacts to key performance parameters such as system sensitivity, dynamic range, noise figure, and radiated power. Understanding this impact is critical in determining whether the design change impact is isolated only to the conversion coating or whether it propagates to other subcomponents to compensate for the loss in performance. The standard way to quantify the electrical resistance of conversion coatings is defined by MIL-DTL-81706B. The test involves collecting a DC resistance measurement on a processed panel using a two-probe measurement with 200 psi of pressure applied to the probes. The resulting value is averaged from 10 samples of data collected across the panel. While this test in MIL-DTL-81706B is well defined, it has significant limitations that caused this research to seek another way to quantify this value. First, the repeatability of the two-point probe is not consistent across the panel. Some of the conversion coatings can be brittle and can easily be disturbed by the force applied by the probes. The poor repeatability is exacerbated when the test articles are environmentally exposed, leaving a non-uniform surface. Finally, this test methodology is performed at DC, which does not directly quantify the impact of the coating at microwave frequencies due to phenomena such as skin effect and potential plasmonic response. This talk discusses an experiment performed to assess the impact of the use of type-II conversion coatings on microwave loss. In order to assess this impact, a set of precision machined waveguide structures were used as test articles in the experiment. The advantage of using this waveguide-based approach is that it provides a distributed surface to assess the average impact of conversion coatings on surface resistivity. This average resistivity more closely maps to the RF losses seen by microwave systems. In addition, testing the waveguide test article provides a very repeatable test methodology; waveguide technology is very mature from a manufacturing perspective. Also, the waveguide flanges provide a repeatable way to connect to the test article so long as they are masked or cleaned after any potential environmental exposure. Finally, the rectangular shape of the waveguide can be canonically described by a closed form expression, improving understanding of the specific mechanisms leading to the loss. This talk discusses an experiment where multiple 3-foot pieces of WR-28 were used as test articles. The WR-28 test articles were chosen to assess the impact to performance at Ka-band. The 3-foot sections are convenient articles because they can easily be measured on a workbench while at the same time being electrically long at Ka-band (on the order of 100 wavelengths). This talk discusses three different populations of test articles, each coated with a different type of conversion coating. This talk also discusses how an initial measurement of these test articles before environmental exposure showed little difference between these populations. Finally, this talk will discuss plans for environmental testing and in-process RF measurements to be captured during these tests.

A comparative study of enhancements of critical temperature in Bi-Pb-Sr-Ca-Cu-O superconductors

In this work, the effects of sintering temperature and Na subtitution on zero critical temperature (Tc,0) in Bi-Pb-Sr-Ca-Cu-O superconductors were investigated. The Bi1.6Pb0.4Sr2Ca2-xNaxCu3O10+d bulk samples with x = 0.00 and 0.05 (BPSCCO) were prepared by using the solid state reaction technique at elevated sintering temperatures of 840 and 850oC. To examine the improvements of structural and superconducting properties of the BPSCCO samples, the X-ray diffraction (XRD), scanning electronic microscope (SEM) and DC resistance versus temperature (R-T) measurements were carried out. The experimental findings exhibit a co-existence of the high Tc (Bi-2223) and low Tc (Bi-2212) phases in all samples. The estimated volume fraction of the Bi-2223 phase was increased from 71.4 to 75.7%, and the average size of the Bi-2223 grains was enlarged from 4.5 to 9.8 mm as changing the sample preparation conditions. The improved connectivities between the Bi-2223 grains were also obtained by quantitively analyzing the relation between Tc,0 and residual resistance ratio (RRR). These improvements were likely to be reasons for the enhancements of Tc,0 in the BPSCCO samples.

Pressure induced superconductivity in very lightly doped LaFeAsO0.975F0.025

We have investigated whether or not superconductivity is induced by the application of pressure in very lightly F-doped LaFeAsO1−xFx, which shows spin density wave (SDW) state at ambient pressure, through the measurements of DC magnetization and electrical resistivity under pressure using pulse current sintered (PCS) high density polycrystalline specimens. It has been confirmed that the specimens with x = 0.025 shows superconductivity with Tcdia∼15 K under pressure above ∼ 1.3GPa. The pressure induced superconductivity can be explained by the lattice compression along c-axis, which enhances the electron doping from LaO layers to FeAs layers.

An effective research for diffusion annealing temperature and activation energy in Au surface-layered Bi-2212 ceramic composites

This study tries to respond two fundamental questions such as (I) what is the role of Au inclusions in the Bi-2212 polycrystalline materials prepared at the diffusion annealing temperature of 600–850 °C on the stabilization of superconductivity in small homogeneous regions and (II) what are the diffusion coefficient and corresponding activation energy of Au inclusions for the Bi-2212 superconducting system. Solution of the former question is in association with the characteristic pairing and coherence transitions extracted from the detailed dc resistivity versus temperature measurements when the latter questions are answered by the change of sample resistivity after the removal of thin-layer from the surface with the aid of the Arrhenius relation for the first time. The experimental measurement results show that the optimum diffusion annealing temperature is observed to be 800 °C where the minor phase, local structural distortions, dislocations, lattice defects and disorders in the Bi-2212 compounds degrade considerably and reach the global minimum points. Similarly, the Josephson coupled energy resides in the maximum value, and thus the superconducting grains become more and more coupled due to the increment in the percolation of intergrains. Moreover, the diffusion coefficient of Au individuals is obtained to increase regularly from 3.6186 × 10−8 to 2.79278 × 10−7 cm2 s−1 with the enhancement in the diffusion annealing temperature. At the same time, the temperature-dependent diffusion coefficient and related activation energy values of Au are computed to be about 2.601 × 10− 6 cm2 s−1 and 1.523 eV, respectively. According to the results calculated, 1.523 eV is the required minimum activation energy for the penetration of Au (heavy metal) ions into the Bi-2212 crystal structure.

Studies of structural, morphological, electrical, and magnetic properties of Mg-substituted Co-ferrite materials synthesized using sol-gel autocombustion method

In this work,a nonmagnetic Mg partially substituted in CoFe2O4 was considered and has been shown to have an impact on structural, electrical and magnetic properties of ferrite materials with Co1−xMgxFe2O4 (x = 0, 0.25, 0.45, and 0.75) forms. Sol-gel synthesis route has been followed to synthesize these materials using citric acid as a fuel. Structural parameters were calculated from powder X-ray diffraction data. X-ray diffraction revealed that all the samples synthesized are pure cubic spinel structured materials with space group of Fd3̅m and the lattice constant varying with Mg concentration. From the field emission scanning electron microscopy (FESEM) microstructure characterizations it has been shown that the synthesized materials are well defined crystalline structured with inhomogeneous grain sizes. Besides, the grain sizes were shown to decrease with increase of Mg-content. Fourier transform Infrared (FT-IR) characterization showed the cation vibrations and stretching of other groups in the wave number range of 400–4000cm−1. The DC resistivity measurements showed an enhanced resistivity of the samples, in the order of 107Ωcm, at the highest concentration of Mg. VSM magnetic properties analysis revealed that the Coercive force decreases with increase of Mg concentration whereas the saturation magnetization varies with Mg content.

Pinning effects on flux flow instability in epitaxial Nb thin films

The flux flow properties of epitaxial niobium films with different pinning strengths are investigated by dc electrical resistance measurements and mapped to results derived within the framework of a theoretical model. The cases of weak random pinning in as-grown films, strong random pinning in Ga ion-irradiated films, and strong periodic pinning induced by a nanogroove array milled by a focused ion beam are investigated. The generic feature of the current–voltage curves of the films consists of instability jumps to the normal state at some instability current density j* as the vortex lattice reaches its critical velocity v*. While monotonically decreases for as-grown films, the irradiated films exhibit a non-monotonic dependence attaining a maximum in the low-field range. In the case of nanopatterned films, this broad maximum is accompanied by a much sharper maximum in both and , which we attribute to the commensurability effect when the spacing between the vortex rows coincides with the location of the grooves. We argue that the observed behavior of can be explained by the pinning effect on the vortex flow instability and support our claims by fitting the experimental data to theoretical expressions derived within a model accounting for the field dependence of the depinning current density.

Evaluation of Automatic Coaxial Mechanical Scanners for Precise Resistance and Capacitance Measurements

In this paper, we evaluated automatic four-terminal-pair and two-terminal-pair coaxial mechanical scanners for precise dc resistance and capacitance measurements. These scanners mechanically change a set of four-terminal-pair or two-terminal-pair BNC connections with coaxial cables using servocontrolled motors. Although originally designed for calibrating the impedance, we evaluated their performance in automating and improving high-resistance measurements. We compared the measured resistance ratios with and without the scanners in the range $1~ {\Omega }$ –1 $\text{T} {\Omega }$ . The results are found to agree to within about 10% of the expanded uncertainty. We also used the scanners to conduct precise 10-pF capacitance measurements at 1 and 1.592 kHz. The measured capacitance differences and the loss angle differences agree with the direct measurements to within the expanded uncertainty.

Effect of (Mn-Co) co-doping on the structural, morphological, optical, photoluminescence and electrical properties of SnO2

Mn and Mn-Co doped SnO2 have been successfully synthesized using co-precipitation technique. The structural properties and surface morphology were studied using x-ray diffractometer (XRD) and scanning electron microscopy (SEM) respectively. Composition analysis of the samples has been carried out from EDX data. Optical properties were studied using reflectance spectroscopy in the wavelength range 200 nm-800 nm and IR absorption spectroscopy in the wave number range 400 cm−1–4000 cm−1. Reflectance spectra revealed that the band gap of prepared samples changes with doping concentration and found to be in the range 3.91 eV–3.95 eV. Infrared (IR) absorption spectra describe the different mode of band related to a functional group present in the materials. Mn and Mn-Co doped SnO2 exhibit very strong emission near the wavelength 413 nm and 434 nm. DC resistivity measurement shows that the activation energy increases with increasing concentration of dopant.

Infrared ellipsometry study of photogenerated charge carriers at the (001) and (110) surfaces of SrTiO3 crystals and at the interface of the corresponding LaAlO3/SrTiO3 heterostructures

With infrared (IR) ellipsometry and DC resistance measurements we investigated the photo-doping at the (001) and (110) surfaces of SrTiO$_3$ (STO) single crystals and at the corresponding interfaces of LaAlO$_3$/SrTiO$_3$ (LAO/STO) heterostructures. In the bare STO crystals we find that the photo-generated charge carriers, which accumulate near the (001) surface, have a similar depth profile and sheet carrier concentration as the confined electrons that were previously observed in LAO/STO (001) heterostructures. A large fraction of these photo-generated charge carriers persist at low temperature at the STO (001) surface even after the UV light has been switched off again. These persistent charge carriers seem to originate from oxygen vacancies that are trapped at the structural domain boundaries which develop below the so-called antiferrodistortive transition at T* = 105 K. This is most evident from a corresponding photo-doping study of the DC transport in STO (110) crystals for which the concentration of these domain boundaries can be modified by applying a weak uniaxial stress. The oxygen vacancies and their trapping by defects are also the source of the electrons that are confined to the interface of LAO/STO (110) heterostructures which likely do not have a polar discontinuity as in LAO/STO (001). In the former, the trapping and clustering of the oxygen vacancies also has a strong influence on the anisotropy of the charge carrier mobility. We show that this anisotropy can be readily varied and even inverted by various means, such as a gentle thermal treatment, UV irradiation, or even a weak uniaxial stress. Our experiments suggest that extended defects, which develop over long time periods (of weeks to months), can strongly influence the response of the confined charge carriers at the LAO/STO (110) interface.

The crossover of (Ba1−xCax)(Ti0.9Sn0.1)O3 piezoelectric ceramics from single-phase to composite with studying the structural and dielectric properties

Lead-free (Ba1−xCax)(Ti0.9Sn0.1)O3 perovskite ceramics (x = 0.02–0.5) (BCTS) were synthesized using the solid-state reaction technique. X-ray diffraction was used to identify the formed phases of the prepared compositions. The morphology of ceramics has been studied using a scanning electron microscope equipped with an energy dispersive spectrometer. Field emission scanning electron microscope was used to examine the morphology of sensing film calcined powder. The crossover from BCTS single-phase (x = 0.02) to BCTS composite(x = 0.5) was obtained via coexistence of both (x = 0.3) of Ca addition. The composite powder was sintered at higher temperature rather than the single-phase powder. The calcined powder sensing film was prepared by the screen-printing technique as humidity sensors. Thereafter, DC resistance measurements were performed in the presence of relative humidity RH at room temperature. All the compositions exhibited a poor sensitivity toward the humidity sensing in the range of 0–98% RH. The compositions 0.02 and 0.06 have shown orthorhombic–tetragonal phase transition (TO−T) below the room temperature, while the other compositions have shown a pure tetragonal phase. The highest value of permittivity at Curie temperature (e = 29241 at 100 Hz) and piezoelectric coefficient (d33 = 495 pC/N) at room temperature were obtained at Ca = 0.06 due to present polymorphic phase transition. The effect of frequency on the dielectric constant and dielectric loss at room temperature were investigated. All the prepared compositions exhibited small values of dielectric loss from 50 Hz up to 100 KHz, which indicates a good reliability for electronic applications such as capacitors or memory devices.

Evidence of spin-glass like ordering and exchange bias effect in antisite-disordered nanometric La1.5Ca0.5CoMnO6 double perovskite

Single-phase polycrystalline La1.5Ca0.5CoMnO6 double perovskite nanoparticles (∼25nm) have been synthesized by chemical sol-gel method. We report here the structural, magnetic and transport properties using X-ray diffraction, dc magnetization, ac susceptibility, exchange bias and dc resistivity measurements. The Rietveld refinement of X-ray diffraction pattern reveals that the La1.5Ca0.5CoMnO6 (LCCMO) system crystallizes in orthorhombic structure with pbnm space group. Mn and Co ions are not completely ordered on the B sites due to the presence of about 30% antisite-disorder in the system. The ordering of Co2+ and Mn4+ gives rise to the ferromagnetism below 145K. A spin glass like ground state has also been observed near 37.6(4)K, arising mainly due to the presence of competing magnetic interactions and antisite-disorder in the LCCMO nanoparticles. The frequency dependence peak shift of the Ac-susceptibility peak in the glassy state follows the critical slowing down model. The observed memory effect in ac susceptibility data reveals the existence of interacting clusters in a competing magnetic interactions state. The presence of noticeable exchange bias effect can be best explained on the basis of uncompensated interface (ferromagnetic/spin-glass) spins of antisite-disordered LCCMO system. This anti-site disordered nanocompound exhibits semiconducting behavior with variable range hopping kind of electronic conduction mechanism in the temperature range of 200–300K. We have also observed large negative magnetoresistance (−30% at 100K and 60kOe) mainly due to the spin-polarized transport across the grain boundaries.

Impedance and DC resistivity studies on chromium substituted cobalt ferrite

Nanocrystalline chromium substituted cobalt ferrite has been prepared by the sol–gel method. XRD analysis reveals that the samples crystallize to cubic symmetry with $$Fd\stackrel{-}{3}m$$ spacegroup. Two transition temperatures (T D ~450 and T M ~600 K) have been observed from the impedance versus temperature measurement. T D increases with the increase in frequency due to dipole response to the frequency. T M is comparable with the para-ferrimagnetic transition temperature of cobalt ferrite, which is independent of frequency. This result is well supported by the temperature dependent DC resistivity measurement. The modified Debye relaxation could explain the impedance spectra of CoFe2−xCrxO4. The grain and grain boundary effect on impedance spectroscopy has been observed from Cole–Cole analysis. The ac conductivity follows Arrhenius behavior at different frequencies. All the samples exhibit the negative temperature coefficient of resistance behavior which reveals the semiconducting behavior of the material. The Mott VRH model could explain the DC electrical resistivity. Both ac impedance and DC resistivity are well co-related with each other to explain the electron transport properties in Cr substituted cobalt ferrite. The electrical transport properties could be explained by the electron hopping between different metal ions via oxygen in the material.

From telegraphy to the revised SI [Basic Metrology

The most reproducible measurements of dc resistance are made with a four-terminal circuit. Two of the terminals carry electrical current through the resistive element and two are used to pick off the potential difference, or voltage, between opposite ends of the element. If the resistance is known and the voltage is measured, then the current flowing through the device is determined by Ohm's law.

Application of emitter-sample hybrid terahertz time-domain spectroscopy to investigate temperature-dependent optical constants of doped InAs.

We investigate temperature-dependent carrier dynamics of InAs crystal by using reflection-type terahertz time-domain spectroscopy, particularly with a recently developed emitter-sample hybrid structure. We successfully obtain the optical conductivity in a terahertz frequency of bulk InAs whose dc conductivity is in the range of 100-150 Ω-1 cm-1. We find that both real and imaginary parts of the optical conductivity can be fit well with the simple Drude model, and the free-carrier density and the scattering rate obtained from the fit are in good agreement with corresponding values obtained by using other techniques, such as the Hall measurement and the dc-resistivity measurement. These results clearly demonstrate that the proposed technique of adopting the emitter-sample hybrid structure can be exploited to determine temperature-dependent optical constants in a reflection geometry and hence to investigate electrodynamics of bulk metallic systems.

Low temperature magnetic properties of frustrated pyrochlore ferromagnet Ho2Ir2O7

We have performed low temperature magnetic susceptibility, specific heat, electrical resistivity and neutron diffraction measurements to study the magnetic properties of frustrated pyrochlore ferromagnet Ho2Ir2O7. The magnetization and dc resistivity measurement indicate metal-insulator transition near 140 K. The accumulated value of observed entropy calculated from heat capacity data is Rln2, indicating the Ho3+ doublet ground state. The Ir sublattice order is antiferromagnetic which is evident from the magnetization measurements. The best fit of the neutron diffraction spectra at 1.8 K shows the magnetic structures with two types of components. One of the magnetic structure is all-in-all-out type, which is due to the strong coupling between Ho3+ and Ir4+ ions and develops below 18 K. It suggests that the magnetic moment of Ho3+ ions align in the field of Ir4+, ordering along local <111> directions. There is also a Ho3+ magnetic component perpendicular to <111> below 100 K. This perpendicular component may originate from the defects in the Ir sub-lattice. Defects such as Ir deficiency or an Ir atom pointing at the opposite direction will cause the emergent of the perpendicular component.

Effect of Charge Reservoir Layer on the Structural and Transport Properties of CuTlBa2−YSr Y -1223 (Y = 0 − 0.25) Superconductor

The bulk superconducting composites Cu0.5Tl0.5 Ba2−YSrYCa2Cu3O10−δ (Y = 0, 0.15, and 0.25) have been synthesized at an ambient pressure. The techniques used to characterize the samples were X-ray scans, Fourier transform infrared spectroscopy (FTIR), and dc resistivity (ρ) measurements. In CuTl-1223 system, we replaced Sr atom at Ba site and studied the superconducting properties of squeezed charge reservoir layer (CRL). From the XRD analysis, it is confirmed that the samples have orthorhombic structure and the dimensional parameters of the unit cell suppressed with the dopant atom which is most probably due to small in size of Sr atom as compared with Ba. The normal-state resistivity and critical temperatures, i.e., Tc (R = 0) and \(T_{\mathrm {c}}^{\text {onset}}\) are observed to be suppressed. The lower values of critical temperature Tc (R = 0) and activation energy Uo (eV) might be possible due to a weak flux pinning. Accordingly, a reduction of weak links and enhanced insulating nature of inter-grain coupling were observed with the doping of Sr atom in CRL. Moreover, the doping in CRL of Sr atom is also confirmed with the FTIR technique. The intrinsic parameters, i.e., coherence length ξc(0), crossover temperatures (T3D−2D), inter-layer coupling (J), etc. were calculated by fluctuation-induced conductivity (FIC) analysis.

SIMULASI HIDROTERMAL DAERAH KAWAH DOMAS DENGAN PEMODELAN KONTINU 2-D ANOMALI SELF POTENTIAL (SP)

Hydrothermal system research using Self Potential (SP) Method, 2-D DC Resistivity and surface temperature, has been done at Domas Crater (1700 masl). Potential anomaly which is associated with subsurface structure is obtained by SP measurement, whereas temperature measurement is done to get information about surface temperature distribution laterally and resistivity distribution of volcano structures is known by 2-D DC Resistivity measurement. Hydrothermal activities, which cause the existence of SP value, are modeled using this scheme modeling. This schema modeling is validated by comparing the value of SP model with field measurement. The shallow hydrothermal activities at Domas Crater are influenced by meteoric and subsurface water. The velocity of hydrothermal activities are about 10-9 - 10-7 m/s. 16.64% root mean square error is obtained by Comsol modeling, whereas 6.54% root mean square error is obtained by modeling using finite element method.

Re-entrant spin glass behaviour and large magnetocaloric effect in Er2PtSi3

We present the magnetic properties and magnetocaloric effect of ternary intermetallic compound Er2PtSi3 with the orthorhombic Ba2LiSi3-type structure. Dc magnetization, ac susceptibilit, magnetic relaxation, electrical resistivity and specific heat measurements indicate that this system undergoes two magnetic phase transitions from a paramagnetic state sequentially to an antifwerromagnetic state at TN=5.4 K and then to a random spin freezing state at Tf=2.4 K. In addition, the large magnetocaloric effect is also observed for the Er2PtSi3 alloy. Near its Néel temperature TN, the maximum magnetic entropy change, relative cooling power and maximum adiabatic temperature change are estimated to be 16.1 Jkg-1K-1, 290 Jkg-1 and 7.7 K, respectively, for a field change of 5 T. These results suggest that Er2PtSi3 should be classified as a re-entrant spin-glass system and can be considered as a potential low-temperature magnetic refrigeration material.