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We investigate the magnetic and crystal electric field (CEF) states of the Kondo lattice system CeCuGa3 by muon spin relaxation (muSR), neutron diffraction, and inelastic neutron scattering (INS) measurements. A noncentrosymmetric BaNiSn3-type tetragonal crystal structure (space group I4mm) is inferred from x-ray as well as from neutron powder diffraction. The low-temperature magnetic susceptibility and heat capacity data show an anomaly near 2.3 - 2.5~K associated with long range magnetic ordering, which is further confirmed by muSR and neutron diffraction data. The neutron powder diffraction collected at 1.7 K shows the presence of magnetic Bragg peaks indexed by an incommensurate magnetic propagation vector k = (0.148, 0.148, 0) and the magnetic structure is best described by a longitudinal spin density wave with ordered moments lying in ab-plane. An analysis of the INS data based on a CEF model reveals the presence of two magnetic excitations near 4.5 meV and 6.9 meV. The magnetic heat capacity data suggest an overall CEF splitting of 20.7 meV, however the excitation between 20 and 30 meV is very broad and weak in our INS data, but could provide an evidence of CEF level in this energy range in agreement with the magnetic entropy. Our analysis of INS data based on the CEF-phonon model indicates that the two excitations at 4.5 meV and 6.9 meV have their origin in CEF-phonon coupling (i.e. splitting of one CEF peak into two peaks, called vibron), with an overall splitting of 28.16 meV, similar to the case of CeCuAl3 and CeAuAl3., 13 pages, 14 figures

The cerium-based compound $\mathrm{Ce}{\mathrm{Pt}}_{6}{\mathrm{Al}}_{3}$, in which Ce atoms form a honeycomb lattice hosting magnetic frustration, has a heavy-fermion ground state. We have observed development of magnetic order in partially Pd-substituted $\mathrm{Ce}{({\mathrm{Pt}}_{1\ensuremath{-}x}{\mathrm{Pd}}_{x})}_{6}{\mathrm{Al}}_{3}$ series up to $x$ = 0.3 by the measurements of magnetic susceptibility, electrical resistivity \ensuremath{\rho}, and specific heat $C$. In the whole range of $x$, the unit cell volume remains unchanged within 0.2%, and the effective magnetic moment stays at $2.4\phantom{\rule{0.16em}{0ex}}{\ensuremath{\mu}}_{B}/\mathrm{Ce}$. For $x$ = 0.05, both $C/T$ and $\ensuremath{\rho}(T)$ jump on cooling at ${T}_{m}=1.8\phantom{\rule{0.28em}{0ex}}\mathrm{K}$. With increasing $x$ to 0.2, ${T}_{m}$ increases to 3.8 K, where $C/T$ shows a pronounced \ensuremath{\lambda}-type anomaly. Application of magnetic fields suppresses ${T}_{m}$, which is indicative of an antiferromagnetic (AFM) ordered state. Thus, a long-range AFM order is induced by the substitution of isovalent Pd for Pt in $\mathrm{Ce}{\mathrm{Pt}}_{6}{\mathrm{Al}}_{3}$ without carrier doping and chemical pressure. We attribute the emergence of AFM order in $\mathrm{Ce}{({\mathrm{Pt}}_{1\ensuremath{-}x}{\mathrm{Pd}}_{x})}_{6}{\mathrm{Al}}_{3}$ to the randomness in the spin-orbit interaction in the Pt-Pd sublattice, which weakens both the coherent Kondo effect and magnetic frustration in the honeycomb Kondo lattice.

An approach to tailor the morphology and sensing characteristics of CuO nanoplatelets for selective detection of NO2 gas is of great significance and an important step toward achieving the challeng...

We report on the effect of α-Fe₂O₃ phase in the magnetic properties and magnetic interactions in nickel ferrite (NiFe₂O₄-NFO) nanoparticles synthesized by co-precipitation method. Structural analysis confirms the formation of the cubic inverse spinel phase without any impurities for the NFO sample annealed in air at 650 °C. When the annealing temperature is increased to 750 °C and 850 °C, α-Fe₂O₃ impurity phase is formed along with the parent NFO phase. Raman spectra recorded at room temperature (RT) confirm the presence of pure NFO phase for the sample annealed at 650 °C, and presence of α-Fe₂O₃ phase is observed in the samples annealed at 750 °C and 850 °C. Saturation magnetization values at RT for the NFO samples annealed at 650 °C, 750 °C and 850 °C are 34 emu/g, 19 emu/g and 28 emu/g respectively. Zero Field Cooled (ZFC) and Field Cooled (FC) measurement reveals the super-paramagnetic behavior along with competing magnetic interactions in all the samples. For the NFO sample annealed at 750 °C and 850 °C, a drop in ZFC magnetization and a small kink in FC magnetization observed around 245 K indicate the presence of a Morin transition (TM) from the α-Fe₂O₃ phase. Anisotropy constants were calculated for all the samples using the law of approach to saturation (LAS) method. The magnetocrystalline anisotropy energy distribution function for the NFO samples annealed at 750 °C and 850 °C exhibit broad peak due to the random distribution of spins associated with different particle size.

Electronic structures and magnetic behaviours of zinc oxide nanorods (ZnO-NRs) decorated with nanocrystalline “Au”-particles (nc-Au) have been studied using different spectroscopies, superconducting quantum interference device-type magnetometer and plane wave pseudopotential density functional theory calculations. The presence of intrinsic defects viz. zinc interstitials (Zni) and/or oxygen vacancies (VO) are established using different spectroscopies measurements. Ultraviolet photoelectron spectroscopy and valence band photoemission spectroscopy suggests that the valence band density of states of O 2p - Zn 4sp hybridized states of nc-Au/ZnO-NRs is higher than pure ZnO-NRs that could be correlated with its higher ferromagnetic behaviour. An enhanced room temperature ferromagnetism has been observed when nanocrystalline (nc) gold (Au) particles are decorated on the surface of ZnO-nanorods (ZnO-NRs). This enhanced magnetic moment in nc-Au/ZnO-NRs comes from the metallic electrons of nc-Au that induces large orbital magnetic moment at the nc-Au/ZnO-NR interface. Theoretical calculations shows the enhancement of the density of states at the valence band region of ZnO with a decoration of optimum content nc-Au particles along with the increase of oxygen vacancies in nc-Au/ZnO-NRs; that further confirms the enhancement of magnetization.

We have synthesized graphene-oxide (GO) by the modified hummer's process and subsequently reduced it with gold-nanoparticles (Au-NPs) using silica coated colloidal Au-NPs and hydrazine monohydrate solutions to form r-GO:Au-NPs nanocomposites. We have studied the microstructure, electronic, electrical and magnetic properties of r-GO and r-GO:Au-NPs nanocomposites. We have observed from the Raman spectroscopy that the intensity of D-peak (disorder) gets reduced with respect to G (graphite-cluster) in r-GO:Au-NPs composites. The reduction of ID/IG ratio obtained from Raman spectra [r-GO: 1.22 → r-GO:(Au-NPs)4.88: 0.98] clearly indicates that the sp2-cluster is reduced in r-GO:Au-NPs nanocomposites. The reduction of sp2-cluster and/or enhancement of sp3-cluster is due to replacement of sp2-cluster by the Au-NPs. This observation also observed from the X-ray absorption near edge structure (XANES) spectroscopy, X-ray photoelectron spectroscopy (XPS) measurements that are consistence with reduction of conductivity as we observe from the current (I) - voltage (V) characteristics of the nanocomposites. Magnetic M-H hysteresis loops show the magnetization is enhanced in r-GO:Au-NPs nanocomposites. We believe that the reduction of conductivity and enhancement of magnetization of r-GO:Au nanocomposites would be most suitable for ferro-electro-magnetic materials for the memory storage device applications.

We report on magnetocapacitance, spin dynamics through AC succeptability measurements and dielectric anomalies in 0.3NiFe2O4 – 0.7BiFeO3 nanocomposite. Structural studies (purity and phase) and surface morphology of the 0.3NiFe2O4 – 0.7BiFeO3 nanocomposite were examined by X-ray diffraction (XRD), Raman Spectra, transmission electron microscopy (TEM) and scanning electron microscopy (SEM). TEM and SEM images indicate the uniform distribution of nanoparticles in parent pahase as well as in the composite. Energy dispersive X-ray (EDX) analysis indicates the presence of Ni, Fe, O and Bi elements in 0.3NiFe2O4 – 0.7BiFeO3 nanocomposite. Magnetization measurements were performed at 300 K, 50 K and at 2 K and the Field Cooled (FC) and Zero Field Cooled (ZFC) measurements were carried out from 350 K to 2 K. ZFC and FC magnetization curves exhibit a hump around 30 K indicating the existence of competing magnetic interactions and possible spin galss behaviour. AC succeptibility measurements at various frequencies confirm the spin glass freezing behaviour of 0.3NiFe2O4 – 0.7BiFeO3 nanocomposite around 25 K with the relaxation time and activation energy in the order of 10−7 s and 0.938 meV respectively. The dielectric constant and dielectric loss at various frequencies and temperatures indicate the dielectric relaxation behaviour of 0.3NiFe2O4 – 0.7BiFeO3 nanocomposite. A rapid increase in the dielectric constant near the antiferromagnetic transition temperature (TN ∼ 643 K) of BiFeO3 indicates the existence of magneto-electric coupling in this composite. Magnetocapacitance (MC) of 0.3NiFe2O4 – 0.7BiFeO3 composite was measured at room temperature and the MC values of 13.5% and 7.8% (at 5000 Oe) are observed when the pellet is perpendicular and parallel to the magneticfield direction respectively. The presented magnetic and dielectric studies reveal the existence of magnetoelectric coupling and spin glass frezing of 0.3NiFe2O4 – 0.7BiFeO3 nanocomposite.

Nanostructured Zn- and Al-doped cobalt spinel ferrites ZnxCo1-xFe2-xAlxO4 (0 ≤ x ≤ 1.0) with particle size in the range of 7–13 nm were synthesized by glycol-thermal reaction. XRD analysis confirmed single-phase cubic spinel structure with no impurity phases. The Mossbauer spectra for Zn- and Al-substituted fine powders could be resolved into two quadrupole doublets associated with 57Fe nuclei in paramagnetic spin phase. An unusual reducing magnetization with increasing particle size has been observed. The field cooled and zero field cooled magnetization measurements show superparamagnetic nanoparticles in the compounds investigated. The blocking temperatures (TB) are sensitive to particle size. Larger particles are blocked at higher temperatures compared to smaller particles at the same field.

We report the signatures of dynamic spin fluctuations in the layered honeycomb ${\mathrm{Li}}_{3}{\mathrm{Cu}}_{2}\mathrm{Sb}{\mathrm{O}}_{6}$ compound, with a $3d S=1/2 {d}^{9}\phantom{\rule{4pt}{0ex}}{\mathrm{Cu}}^{2+}$ configuration, through muon spin rotation and relaxation ($\ensuremath{\mu}\mathrm{SR}$) and neutron scattering studies. Our zero-field (ZF) and longitudinal-field (LF) $\ensuremath{\mu}\mathrm{SR}$ results demonstrate the slowing down of the ${\mathrm{Cu}}^{2+}$ spin fluctuations below 4.0 K. The saturation of the ZF relaxation rate at low temperature, together with its weak dependence on the longitudinal field between 0 and 3.2 kG, indicates the presence of dynamic spin fluctuations persisting even at 80 mK without static order. Neutron scattering study reveals the gapped magnetic excitations with three modes at 7.7, 13.5, and 33 meV. Our density functional theory calculations reveal that the next-nearest-neighbor (NNN) antiferromagnetic (AFM) exchange (${J}_{\text{AFM}}=31$ meV) is stronger than the NN ferromagnetic (FM) exchange (${J}_{\text{FM}}=\ensuremath{-}21$ meV), indicating the importance of the orbital degrees of freedom. Our results suggest that the physics of ${\mathrm{Li}}_{3}{\mathrm{Cu}}_{2}\mathrm{Sb}{\mathrm{O}}_{6}$ can be explained by an alternating AFM chain rather than the honeycomb lattice.

Here we report the magnetic, electronic and thermal transport properties of the heavy-fermion semimetal Pr

Reduced dimensionality offers a piece of crucial information in deciding the type of the quantum ground state in heavy fermion materials. Here we have examined the stoichiometric ${\mathrm{CeCo}}_{2}{\mathrm{Ga}}_{8}$ compound, which crystallizes in a quasi-one-dimensional crystal structure with Ga-Ce-Co chains along the $c$ axis. The low-temperature behavior of the magnetic susceptibility ($\ensuremath{\chi}\ensuremath{\sim}{T}^{\ensuremath{-}0.2}$), heat capacity (${C}_{p}/T\ensuremath{\sim}\ensuremath{-}lnT$), and resistivity ($\ensuremath{\rho}\ensuremath{\sim}{T}^{n}$ with $n\ensuremath{\sim}1$) strongly confirms the non-Fermi liquid ground state of ${\mathrm{CeCo}}_{2}{\mathrm{Ga}}_{8}$. We study the low-energy spin dynamics of the ${\mathrm{CeCo}}_{2}{\mathrm{Ga}}_{8}$ compound utilizing zero-field (ZF) and longitudinal-field muon spin relaxation ($\ensuremath{\mu}\mathrm{SR}$) measurements. ZF-$\ensuremath{\mu}\mathrm{SR}$ measurement reveals the absence of long-range magnetic ordering down to 70 mK. Interestingly, below 1 K the electronic relaxation rate rises sharply, suggesting the appearance of low-energy quantum spin fluctuations in ${\mathrm{CeCo}}_{2}{\mathrm{Ga}}_{8}$.

International audience; We report on the synthesis and physical properties of the new ternary intermetallic Ce2Rh2Ga. Its formation and dimorphism have been investigated by powder and single crystal X-ray diffractometry, as well as by differential thermal analyses. LT-and HT-Ce2Rh2Ga can be obtained by the chosen respective thermal treatment. The high-temperature form (HT-Ce2Rh2Ga), stable above 864(5)degrees C, is orthorhombic La2Ni3-type [Cmce, oS20, a = 5.851(2) angstrom, b = 9.6184(19) angstrom, c = 7.4871(17) angstrom, V = 421.3(2) angstrom(3)]; the low temperature form (LT-Ce2Rh2Ga), stable below this temperature, is monoclinic Pr2Co2Al-(Ca2Ir2Si-) type [C2/c, mS20, a = 10.0903(6) angstrom, b = 5.6041(3) angstrom, c = 7.8153(4) angstrom, b = 104.995(3)degrees C, V = 426.88(4) angstrom 3]. The magnetic measurements were conducted on two different samples, namely on the LT-Ce2Rh2Ga and the other on the HT-Ce2Rh2Ga sample. The HT-Ce2Rh2Ga compound is found to exhibit a phase transition at 128.5 K. By virtue of the sharp peak anomaly in the temperature dependence of the magnetic susceptibility this phase transition is plausibly of antiferromagnetic origin, but occurs at a remarkably high temperature compared to what is typical for Ce binary and ternary compounds. LT-Ce2Rh2Ga has a ground state of ferromagnetic nature which sets in at a paramagnetic-to-ferromagnetic phase transition at 5.2 K.

The spin–glass behavior in the ferromagnetic phase of Tm 2 Cu 2 In was investigated by dc–, ac–magnetization, and non-equilibrium dynamics characterizations. An argon arc–melted polycrystalline sample of the compound of Tm 2 Cu 2 In was found to adopt the Mo 2 FeB 2 –type tetragonal structure (space group P 4 / m b m ). The temperature variation of dc–magnetization exhibits a ferromagnetic behavior with Curie temperature T C = 32.5 K. The zero field cooled (ZFC) and field cooled (FC) magnetic curves show the thermomagnetic irreversible behavior below T C . The field dependence of irreversible temperature follows the Almeida–Thouless line. The frequency and ac–driven field dependent anomalies in ac–susceptibility results indicate the existence of a spin–glass state in Tm 2 Cu 2 In . The time dependence of magnetization further supports the spin–glass behavior observed in Tm 2 Cu 2 In . The frequency dependence of the freezing temperature in the real part of ac–susceptibility has been analyzed on the basis of a power–law divergence and Vogel–Fulcher law. The obtained results reveal that Tm 2 Cu 2 In belongs to the ferromagnetic canonical spin–glass class of compounds.

We report the synthesis, crystal structure, and thermodynamic properties of the two binary laves phases Ce3Cu and Pr3Cu, which crystallize in the tetragonal I4/mmm (space group: 139). We have investigated the compounds using dc magnetic susceptibility χdc(T), ac magnetic susceptibility χac(T), isothermal magnetization M(B) and specific heat Cp(T) measurements. Both compounds show features of strong geometrical frustration, which is driven by the arrangement of the rare-earth ions on triangular lattice sites. Ce3Cu shows a phase transition at TN = 5 K and its M(B) at 2 K reveals the presence of a metamagnetic transition near 2 T. Pr3Cu, on the other hand, shows a spin-glass behaviour with a freezing temperature of Tf1 ≃ 12 K and with an irreversible behavior in zero-field-cooled (ZFC) and field-cooled (FC) χdc(T) below about 13 K. The real part of χac(T) reveals a frequency dependence of Tf. The result, however shows the presence of another frequency-dependent phase below Tf2 ≃ 9.35 K, a feature which signals a re-entrant spin-glass behaviour in the compound. Furthermore, the frequency dependence of Tf1 follows the Vogel-Fulcher law, with an activation energy Ea∕kB = 5.3 K. This observation along with the estimated relative shift in Tf1 per decade in frequency δTf = 0.0105, irreversible behaviour in ZFC-FC χdc(T) and a slow decay in thermo-remnant magnetization provide supports for the formation of a cluster spin-glass in Pr3Cu. In addition, we observe the enhancement of the Sommerfeld coefficient, γ in both compounds with values of 0.1892(5) J/(molCe K2) and 0.5078(1) J/(molPr K2). The estimation of the Sommerfeld-Wilson ratio WR yield values of 0.576 and 1.17 for Ce3Cu and Pr3Cu, respectively.

We report the structural, magnetic properties, and magnetocaloric effect of a new polycrystalline compound of $\mathrm{Tb_2Rh_3Ge}$. This present compound crystallizes with $\mathrm{Mg_2Ni_3Si}$-type of rhombohedral Laves phases (space group $R\overline{3}m$, hR18). The magnetic properties and magnetocaloric effect of the $\mathrm{Tb_2Rh_3Ge}$ is explored through dc-magnetization measurements. Temperature dependence of magnetization revealed that the compound exhibits ferromagnetic behavior with $T_C$$=$56 K. The field dependence of magnetization indicates that $\mathrm{Tb_2Rh_3Ge}$ is a soft ferromagnet. The obtained isothermal magnetic entropy changes ($\Delta S_m$), and refrigeration capacity (relative power cooling) for a change of magnetic field 0-9 T are 12.74 J/kg-K, and 497(680) J/kg respectively. The Arrott plots and universal curve of normalized $\Delta S_m$ indicate that this compound undergoes second order ferromagnetic phase transition

The Nd 2 Pt 2 In compound was investigated by means of electrical resistivity ρ ( T ) , heat capacity C p ( T ) , magnetic susceptibility χ ( T ) , magnetization M ( μ 0 H ) and magnetocaloric effect (MCE) measurements. The material orders ferromagnetically at T C = 16 K with a second - order phase transition. In the ordered state, ρ ( T ) can be represented in terms of ferromagnetic (FM) spin - wave dispersion with an energy gap Δ R = 13(1) K in zero field. In concert, the C p ( T ) data in this region can be well described by the same model getting Δ C = 8(1) K in zero field. Above T C , the ρ ( T ) variation is characteristic of electron - phonon interaction in the presence of s − d scattering and crystalline-electric field (CEF). The 4 f - electron specific heat shows a Schottky - type anomaly around 60 K associated with CEF. On the other hand, C p ( T ) data of the non-magnetic homologue La 2 Pt 2 In can be described by the Debye - Einstein model, giving a Debye and Einstein temperature values of 190.3(5) K and 69.8(7) K respectively. At high temperatures, the χ ( T ) data follows the Curie - Weiss relation with an effective magnetic moment μ e f f = 3.61(2) μ B and a Weiss temperature θ p = 17(1) K. The magnitude of MCE was estimated from the isothermal magnetization data to be 6.25 J/(kg.K), 5.01 J/(kg.K), 3.18 J/(kg.K) and 0.47 J/(kg.K) for a field change of 7 T, 5 T, 3 T and 1 T, respectively. The characteristic behaviour of the isothermal magnetic entropy change points to a second - order character of the FM phase transition.

The magnetic ordering in Pr 2 Pt 2 In was investigated by means of magnetization and magnetic susceptibility measurements. The compound was found to order ferromagnetically at T C = 8.8(2) K with a second-order phase transition. The derived critical exponents β = 0.325(2), γ = 1.058(2) and δ = 4.26(4) are close to those expected for a 3D Ising ferromagnet.

PrCo$_2$Ga$_8$ is an orthorhombic quasi-skutterudite type compound which crystallizes in the CaCo$_2$Al$_8$ structure type, with space group $Pbam$ (No. 55). The Pr$^{3+}$ ion has a site symmetry of $C_s$ which predicts a crystal electric field (CEF) level splitting into 9 singlets for $J$ = 4. However, a phase transition at $T_m$ = 1.28~K is observed in electrical resistivity and specific heat results and is reported in this paper. The electrical resistivity shows an upturn below $T_m$ due to the superzone-gap formation. This transition is tuneable in fields and is suppressed to lower temperatures with applied magnetic fields. The electronic specific heat $C_{p}(T)/T$ increases below $T_m$ and reaches a value of 7.37 J/(mol K$^2$) at 0.4~K. The Sommerfeld coefficient, $\gamma$ extracted from the low temperature analysis of $C_\mathrm{4f}(T)/T$ is 637 mJ/(mol K$^2$) indicating a possible mass enhancement of the quasiparticles. The calculated entropy value of 3.05 J/(mol K) is recovered around $T_m$ exhibiting almost 53% of Rln2, where R is the universal gas constant. Magnetic susceptibility results obeys the Curie-Weiss law for data above 100 K with an estimated effective magnetic moment, $\mu_\mathrm{eff}$ = 3.37 $\mu_B$/Pr and Weiss temperature, $\theta_p$ = $-$124 K., Comment: 11 pages, 5 figures, SCES 2017 conference proceedings

We report on X-ray diffraction, electrical transport, heat capacity and magnetocaloric effect measurements of a polycrystalline sample of Pr 2 Pt 2 In . The compound forms in the tetragonal Mo 2 FeB 2 type structure and orders ferromagnetically at T C =9 K. In the ordered state, its thermodynamic and electrical transport properties are dominated by magnon contributions with an energy gap of about 8 K in the spin-wave spectrum. The magnitude of magnetocaloric effect is similar to the values reported for most rare-earth based intermetallics. Characteristic behavior of the isothermal magnetic entropy change maximum points to a second-order character of the ferromagnetic phase transition in the compound studied.

The orthorhombic, space group Cmcm YbFe 2 Al 10 structure type series of compounds are known to form with practically the entire series of rare-earth elements R, but only with the three d − electron elements Fe, Ru, and Os. The Ce-derivatives in particular have been of much interest since the first reports of their highly unusual physical properties. Classified as Kondo insulators, CeRu 2 Al 10 and CeOs 2 Al 10 controversially order magnetically and with uncharacteristically high Neel temperatures of ≃ 28 K. CeFe 2 Al 10 on the other hand shows pronounced semiconducting and Kondo features but remains paramagnetic. As part of our ongoing studies into the rich physics of this class of materials we have succeeded in synthesizing new members of the 1:2:10 stoichiometry involving the chemical element Rh for the first time. CeRh 2 Al 10 is found to crystallize in the tetragonal system with space group I 4 1 / amd . Yb Rh 2 Al 10 on the other hand forms in the serial Cmcm orthorhombic structure type. We discuss important similarities between the two types. At 5.310 A the shortest Ce–Ce distance is, likewise to the situation in CeRu 2 Al 10 and CeOs 2 Al 10 , also well above the Hill limit of 3.40 A. Despite the cage-like structure and large rare-earth separation distances, this study reveals the onset of long-range magnetic ordering in CeRh 2 Al 10 at 3.9 K. The magnetic ordering develops out of an incoherent Kondo state that dominates the electrical resistivity below about 40 K.

The Frank-Kasper cage compound EuV 2 Al 20 crystallizes in the cubic structure with Fd 3 ‾ m space group and exhibits unusual magnetic and transport properties. The system undergoes an antiferromagnetic transition below 5.6 K wherein the Eu 2+ moments are aligned anti-parallel along 〈1 1 1〉 direction and the system exhibits a weak metamagetic transition at the field of 1 T. Arrott plots ( M 2 vs H / M ) show a “S” shaped variation in the low fields below T N and the plausible reason for the occurrence of negative slope is discussed. Isothermal magnetic entropy change is estimated from both magnetization and heat capacity measurements invoking the Maxwell’s thermodynamic relations. Temperature variation of Δ S m showed a weak negative minimum and a sign reversal at the field value of 1 T due to field induced metamagnetic transition. Universal master curve is constructed by rescaling the Δ S m vs T curves in the context of analysing the nature of the magnetic transition.

We present an extended research on characterization of the ground state in a polycrystalline compound Ce2Ir3Al9 using powder x-ray diffraction, magnetic susceptibility χ(T), isothermal magnetization M(B), specific heat Cp(T), electrical resistivity ρ(T), magnetoresistivity ρ(B), thermoelectric power S(T) and thermal conductivity κ(T) measurements, together with a theoretical description of the obtained data to develop a more profound understanding of the physics in this compound. Ce2Ir3Al9 crystallizes in the orthorhombic Y2Co3Ga9-type of structure (space group Cmcm, No. 63, oC56, Z = 4). The χ(T) and Cp(T)/T data reveal the signatures of intermediate valence behaviour on Ce ions with the approximate value of the Kondo temperature TK = 96 K and the Sommerfeld coefficient γ = 31 mJ/mol ⋅ K2. In contrast to the magnetometric and thermodynamic measurements, the transport data (ρ(T) and S(T)) indicate the development of the Kondo lattice state. Accordingly, we expect that for Ce2Ir3Al9 the most likely scenario, which develops in a wide T range is the coexistence and competition of two energy scales of interactions between conduction electrons and 4f spins on Ce ions, located in one unique crystallographic site in the unit cell, in consequence carrying out our system from Ce4+ T e m p . → Ce3+. At higher temperatures, where the Kondo interaction becomes dominant the influence of the crystal electric field effect seems to play an influential role in the ground state of this compound too.

The two new rare-earth pyrocoboltates R 2 Co2O7 (R = Ce, Yb) adopt the layered monoclinic Ca2Nb2O7-type structure with the space group P21 (No. 4). Both compounds have been investigated by DC magnetic susceptibility χ dc ( T ) , AC magnetic susceptibility χ ac ( T ) and isothermal magnetization M ( B ) measurements. The observed effective magnetic moment of Ce2Co2O7 indicates a contribution from the Co sublattice while that of Yb2Co2O7 is mainly from the localized 4 f 13 electronic configuration of Yb3+ ion. A magnetic ordering of the antiferromagnetic-type is observed in Ce2Co2O7 at T N ≃ 34 K. This ordering is accompanied by the opening of a magnetic spectral gap, Δ = 57.7 K ( ~ 5.0 meV) in the spin-wave spectrum and it survives in an external magnetic field of 7 T. In addition to the transition at T N , χ ac ( T ) measurements reveal a dome-like feature centered at ≃ 20 K in high frequency which indicates the presence of possible short-range correlation. In Yb2Co2O7, a magnetic phase transition is observed below T N = 2.94 K, which is suppressed below 1.9 K in an external magnetic field of 3 T. In the low-T region where the crystal electric field effects can be neglected, an effective spin-1/2 state is realized in Yb2Co2O7, with a Lande-g factor of 3.76 which is comparable to values observed from electron spin resonance (ESR) measurements on related systems. In addition, M ( B ) of Yb2Co2O7 shows a metamagnetic-like feature at a critical field of H C ≈ 2.5 T. Signatures from both compounds reveal the presence of strong magnetic frustrations with frustration index f of 9.17 and 15.12 for Ce2Co2O7 and Yb2Co2O7, respectively.

We report the magnetic, electronic and transport properties of the quasi-skutterudite compound Pr3Ir4Ge13 by means of magnetic susceptibility χ(T), electrical resistivity ρ(T), specific heat Cp(T), thermal conductivity κ(T), thermoelectric power S(T) and Hall coefficient RH(T) measurements. Pr3Ir4Ge13 does not show any phase transition down to 1.9 K. Magnetic, and specific measurements show that the system possesses a crystal electric field singlet ground state that is separated from the first excited state by about 37 K. ρ(T) shows a negative temperature coefficient of resistance for the whole temperature range studied and which can be explained in terms of Mott’s impurity band conduction mechanism. RH(T) measurements show that Pr3Ir4Ge13 is a low-carrier density semiconductor and its transport properties indicate a metallic-non metallic cross over behaviour. Large Seebeck coefficient was observed for the entire temperature range of investigation, and the analysis of temperature variation of S and S∕T showed no sign of strong correlation between the Pr 4f2 and conduction electron states near Fermi level.

Dc and ac – magnetic susceptibility (χ), specific heat ( C P ), electrical resistivity (ρ) and magnetoresistance measurements performed on the new polycrystalline compound Gd 2 AgSi 3 , crystallizing in the α – ThSi 2 tetragonal structure, are reported. Two magnetic phase transitions were observed in dc and ac susceptibility, specific heat and resistivity measurements at temperatures T N 1 = 11 K and T N 2 = 20 K, despite a single site occupied by Gd atom, which is an indication of the complex magnetic behavior. Gd 2 AgSi 3 turns out be one of the rare Gd compound in which a minimum is observed in the temperature dependence of resistivity in the paramagnetic state and also negative magnetoresistance over a wide temperature range (above T N 2 ), mimicking the behavior of exotic Gd 2 PdSi 3 , in this ternary family. The isothermal magnetic entropy change, adiabatic temperature change, and refrigerant capacity reach a value of 9.5 J/kg-K, 7.5 K and 302 J/kg, respectively for the change of magnetic field 0-9 T.

We report the magnetotransport and thermodynamic properties of PrPtSi which crystallizes with the noncentrosymmetric LaPtSi-type structure (space group: I41md). Signatures from specific heat and magnetic susceptibility reveal an anomaly at T* ≃ 5.5 K which is attributed to crystal field effects. We find a negative magnetoresistance whose magnitude grows with decreasing temperature, with a value of −17.4% at 1.9 K and in 7 T. Results from the electronic-derived specific heat C4f reveal an upturn in C4f(T)/T at low temperature and traces a −logT dependence, attaining values of 1.1 J/(mol K2) and 3.6 J/(mol K2) at 0.38 K in zero and 4 T, respectively.

We report on dielectric anomalies, competing magnetic interactions and relaxor ferroelectric behaviors of xPMN–PT–(1 – x)NiFe2O4 (x = 0.2 and 0.4) nanocomposites. The crystal structure and surface morphology of the pure and composite nanomaterials were examined by X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Phase formation and purity of the NiFe2O4, PMN–PT and the composites were confirmed from XRD measurements. Uniformly distributed nanoparticles and nanowires and the presence of Ni, Fe, O, Pb, Nb, Mg, and Ti in NiFe2O4 and PMN–PT are confirmed from FESEM and energy dispersive X-ray (EDX) measurements. Structural disordering due to phase transition around 453 K in both composites was examined from temperature variation Raman studies. Magnetization measurements at room temperature and at 40 K, zero field cooled (ZFC) and field cooled (FC) magnetization measurements for both composites were carried out from 2 to 350 K. Competing magnetic interacti...

A new member of the RET 2 Al 10 family was synthesized and its crystal structure was determined from single crystal X-ray diffraction. The first aluminide with rhodium adopts a new structure type of 1:2:10 stoichiometry. CeRh 2 Al 10 crystallizes in the tetragonal space group I 4 1 / amd with cell parameters a = 8.9284(11) A and c = 21.769(3) A and is a substitution variant of CePd 3 Al 9 compound. The mutual arrangement of Rh and Al neighbors within the 20-vertex Ce polyhedron differs in comparison with that of the CeRu 2 Al 10 structure. This leads to the different packing of Ce polyhedra in the unit cell. In CeRh 2 Al 10 , zig-zag chains of the shortest Ce Ce contacts extend in the two mutually perpendicular directions – along the a -axis and along the b -axis. In contrast, in CeRu 2 Al 10 , zig-zag chains of the shortest Ce Ce contacts run in one direction – along the c -axis. We illustrate using key physical properties how the variation in crystal structure produces physical properties in CeRh 2 Al 10 that differ strikingly from the situation in CeRu 2 Al 10 .

Graphene oxide potentially used as an intermediary in the production of single layer or few-layer graphene sheets. To achieve this, an oxidization and reduction process is used to developed single/few-layers and separate them without changing their structure. Graphene oxide has potential applications in many areas, e.g., electronics, magnetic, catalysis, and energy storage, because of its high charge-carrier mobility and high specific surface area. This study investigates the electronic and magnetic properties of graphene oxide (GO), and nitrogen functionalised graphene oxide (GO-Nx). GO is prepared using chemical process and hence functionalized with nitrogen precursors. GO and GO-Nx are characterised using X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy and Raman spectroscopy. Nitrogen functionalized GO become more graphitic in structure as observed from Raman spectroscopy and N 1s XPS spectrum that turn into higher magnetization observed from M-H hysteresis loops. The electronic density of states of GO-Nx is significantly higher than as compared to the GO as a result the magnetic properties also enhanced on GO-Nx. Our experimental results thus provide new evidences to control the magnetic and electronic properties of GO and GO-Nx for different electronic and magnetic device applications.

We report on structural, spin glass behaviour and competing magnetic interactions in xNiFe2O4 - (1-x)BaTiO3 (x = 0.2 and 0.3) nanocomposites prepared by sol-gel method. The structure and surface morphology of the NiFe2O4-BaTiO3 composites were examined by X-ray diffraction (XRD) and scanning electron microscope (SEM). XRD measurements of composite materials show the presence of both NiFe2O4 and BaTiO3 phases. FESEM and energy dispersive X-ray (EDX) measurements indicate uniformly distributed nano size particles and presence of Ni, Fe, O, Ba and Ti elements respectively. Temperature variation Raman spectra indicates large structural disordering (Peak broadening and shift) around 395 K due to the structural transformation of BaTiO3. Magnetization, zero field cooled (ZFC) and field cooled (FC) measurements were carried out from 2 K to 320 K for both composites. ZFC and FC measurements reveal the spin glass and Superparamagnetism like behaviour along with competing magnetic interaction in both composites. Saturation magnetization value is seen to increase from 6.7 to 10 emu/g with increasing Ni ferrite composition from x = 0.2 to x = 0.3. Distribution function associated with magnetocrystalline anisotropy energy barrier exhibits broad peaks due to the random distribution of spins associated with different particle size in the x = 0.3 composition.

The alloys Ce 8 Pd 24 ( Al 1 − x Sn x ) with 0 ≤ x ≤ 1 were studied by means of electrical resistivity, thermal conductivity, thermoelectric power, magnetic susceptibility and magnetization measurements. In the entire composition range, an antiferromagnetic (AFM) long-range ordering has been established at low temperatures, with the Neel temperature increasing linearly from T N = 4.3 K for Ce 8 Pd 24 Al to T N = 7 K for Ce 8 Pd 24 Sn . Below T N , the electrical resistivity is dominated by scattering conduction electrons on spin-wave excitations. In the paramagnetic state, the electrical transport in the alloys with 0 ≤ x ≤ 0.7 reveals both coherent Kondo lattice scattering and crystal-electric field (CEF) effect, while that in the alloys with x ≥ 0.8 appears governed by CEF only. Above T N , all the alloys exhibit well localized magnetic behavior due to trivalent Ce ions. At high temperatures, the thermoelectric power can be interpreted in terms of a phenomenological resonance model giving an estimate of the CEF effect. The thermoelectric figure of merit of Al-rich alloys is small compared to those of commercial thermoelectric materials.

The superconducting phase transition at $$T_\mathrm{c} = 2.3$$ K was observed for the electrical resistivity $$\rho ({T})$$ and magnetic susceptibility $$\chi (T)$$ measurements in the ternary compound La $$_{5}\hbox {Ni}_{2}\hbox {Si}_{3}$$ that crystallizes in the hexagonal-type structure. Although a single-phase character with the nominal stoichiometry of the synthesized sample was confirmed, a small trace of the La–Ni phase was found, being probably responsible for the superconducting behaviour in the investigated compound. The magnetization loop recorded at $${T} = 0.5$$ K resembles a star-like shape which indicates that the density of the critical current can be strongly suppressed by a magnetic field. The low- $$T _{\rho }(T)$$ and specific heat $${C}_\mathrm{p}({T})$$ data in the normal state reveal simple metallic behaviour. No clear evidence of a phase transition to any long- or short-range order was found for $$C_\mathrm{p}(T)$$ measurements in the T-range of 0.4–300 K.

The interplay of antiferromagnetic (AFM) and Kondo effect in Ce 8 Pd 24 Al with the dilution of Ce with La is investigated by means of electrical and thermal transport and magnetic properties measurements. X - ray diffraction studies confirm a cubic AuCu 3 - type crystal structure with space group Pm 3 ¯ m for all compositions in the alloy series ( Ce 1 − x La x ) 8 Pd 24 Al ( 0 ≤ x ≤ 1 ) . Electrical resistivity, ρ ( T ) results show evolution from coherent Kondo lattice scattering with a well defined Kondo peak at Tmax to incoherent single-ion Kondo scattering with increasing La content x. Magnetoresistivity MR measurements on Ce dilute alloys are negative and analyzed based on the calculations by Schlottmann for the Bethe - ansatz in the framework of the Coqblin - Schrieffer model and yield values of the Kondo temperature TK and the effective moment of the Kondo ion μK. The decrease of Tmax and TK is described by the compressible Kondo lattice model. The thermoelectric power, S(T) measurements are interpreted within the phenomenological resonance model. The Lorentz number, L / L 0 increases rapidly on cooling the samples and reaches a maximum value around 6 K. The magnetic susceptibility, χ ( T ) data at high temperature follow the Curie - Weiss behaviour and yield effective magnetic moments, μeff values across the series close to the value of 2.54 μB expected for the free Ce 3 + - ion. The low temperature χ ( T ) shows an AFM anomaly associated with a Neel temperature TN for alloys in the range 0 ≤ x ≤ 0.2 . No metamagnetic transition was observed from the magnetization results, M ( μ 0 H ) .

In this article, we report the modification of the electronic and magnetic properties of few-layered graphene (FLG) nanoflakes by nitrogen functionalization carried out using radio-frequency plasma-enhanced chemical vapor deposition (rf-PECVD) and electron cyclotron resonance (ECR) plasma processes. Even though the rf-PECVD N2 treatment led to higher N-doping levels in the FLG (4.06 atomic %) as compared to the ECR process (2.18 atomic %), the ferromagnetic behavior of the ECR FLG (118.62 × 10–4 emu/g) was significantly higher than that of the rf-PECVD FLG (0.39 × 10–4 emu/g) and pristine graphene (3.47 × 10–4 emu/g). Although both plasma processes introduce electron-donating N atoms into the graphene structure, distinct dominant nitrogen bonding configurations (pyridinic, pyrrolic) were observed for the two FLG types. Whereas the ECR plasma introduced more sp2-type nitrogen moieties, the rf-PECVD process led to the formation of sp3-coordinated nitrogen functionalities, as confirmed through Raman measurem...

We report a detailed study of the magnetization modulus as a function of temperature and applied magnetic field under varying angle in Sr$_{4}$Ru$_{3}$O$_{10}$ close to the metamagnetic transition at $H_{c}\backsimeq 2.5\,$T for $H \perp c$. We confirm that the double-feature at $H_{c}$ is robust without further splitting for temperatures below 1.8 K down to 0.48 K. The metamagnetism in Sr$_{4}$Ru$_{3}$O$_{10}$ is accompanied by a reduction of the magnetic moment in the plane of rotation and large field-hysteretic behavior. The double anomaly shifts to higher fields by rotating the field from $H\,\perp \,c$ to $H\,\parallel\,c$. We compare our experimental findings with numerical simulations based on spin reorientation models caused by intrinsic magnetocrystalline anisotropy and Zeeman effect. Crystal anisotropy is able to explain a metamagnetic transition in the ferromagnetic ordered system Sr$_{4}$Ru$_{3}$O$_{10}$, but a Dzyaloshinskii-Moriya term is crucial to account for a reduction of the magnetic moment as discovered in the experiments., Comment: 7 pages, 8 figures

The effects of substituting moment-bearing Tb in CePt 2 Si 2 are reported through X-ray diffraction (XRD), electrical resistivity ( ρ ( T ) ), magnetic susceptibility, ( χ ( T ) ), and magnetization, ( σ ( μ 0 H ) ) measurements. XRD results for all compositions of ( Ce 1 − x Tb x ) Pt 2 Si 2 system indicate a tetragonal CaBe 2 Ge 2 - type structure with space group P 4 / n m m . ρ ( T ) results indicate a rapid evolution from a coherent Kondo lattice for the CePt 2 Si 2 parent compound to incoherent single-ion Kondo behaviour with substitution of Tb for Ce. However, between 90% and 100% of Tb content, the ( Ce 1 − x Tb x ) Pt 2 Si 2 system reverts back to stable local - moment, normal metal behaviour. χ ( T ) data at higher temperature follow the Curie - Weiss relation for all alloy compositions and give effective moment values μ e f f which increase gradually from the expected values of 2.54 μ B for the Ce 3 + - ion to 9.72 μ B for the Tb 3 + - ion. At low temperature χ ( T ) data exhibit antiferromagnetism at the N e ′ el temperature T N in the concentration range 0.7 ≤ x ≤ 1 . Below T N the zero-field-cooled and field-cooled susceptibility bifurcate in a 0.1 T field, suggesting an inhomogeneous magnetic ground state as a result of spin glass - like state for compositions in the range 0.6 ≤ x ≤ 1 . No evidence of metamagnetic behaviour was observed from σ ( μ 0 H ) data for all compositions.

We present magnetization measurements on Sr 4 Ru 3 O 10 as a function of temperature and magnetic field applied perpendicular to the magnetic easy c-axis inside the ferromagnetic phase. Peculiar metamagnetism evolves in Sr 4 Ru 3 O 10 below the ferromagnetic transition T C as a double step in the magnetization at two critical fields H c 1 and H c 2 . We map the H − T phase diagram with special focus on the temperature range 50 K ≤ T ≤ T C . We find that the critical field H c 1 ( T ) connects the field and temperature axes of the phase diagram, whereas the H c 2 boundary starts at 2.8 T for the lowest temperatures and ends in a critical endpoint at (1 T; 80 K). We conclude from the temperature dependence of the ratio Hc 1 Hc 2 ( T ) that the double metamagnetic transition is an intrinsic effect of the material and it is not caused by sample stacking faults such as twinning or partial in-plane rotation between layers.

High-quality single crystals of NaYbSe$_2$, which resembles a perfect triangular-lattice antiferromagnet without the intrinsic disorder, are investigated by magnetization and specific heat, as well as the local probe techniques nuclear magnetic resonance (NMR) and electron spin resonance (ESR). The low-field measurements confirm the absence of any spin freezing or long-range magnetic order down to 50~mK, which suggests a quantum spin liquid ground (QSL) state with gapless excitations. The instability of the QSL state is observed upon applying magnetic fields. For the $H\bot c$ direction, a field-induced magnetic phase transition is observed above 2~T from the $C_{\rm p}(T)$ data, agreeing with a clear $\frac{M_s}{3}$ plateau of $M(H)$, which is associated with an up-up-down (uud) spin arrangement. For the $H\|c$ direction, a field-induced transition could be evidenced at a much higher field range (9 - 21~T). The $^{23}$Na NMR measurements provide microscopic evidence for field-induced ordering for both directions. A reentrant behavior of $T_{\rm N}$, originating from the thermal and quantum spin fluctuations, is observed for both directions. The anisotropic exchange interactions $J_{\perp}\simeq$ 4.7~K and $J_z\simeq$2.33~K are extracted from the modified bond-dependent XXZ model for the spin-$\frac{1}{2}$ triangular-lattice antiferromagnet. The absence of magnetic long-range order at zero fields is assigned to the effect of strong bond-frustration, arising from the complex spin-orbit entangled $4f$ ground state. Finally, we derive the highly anisotropic magnetic phase diagram, which is discussed in comparison with the existing theoretical models for spin-$\frac{1}{2}$ triangular-lattice antiferromagnets., 6 Figures

We have investigated the physical and magnetic properties of the distorted Kagomé lattice structure compounds; Pr[Formula: see text]Al

Features of low-dimensional magnetism resulting from a square-net arrangement of Co atoms in trirutile ${\mathrm{CoTa}}_{2}{\mathrm{O}}_{6}$ are studied in the present work by means of density functional theory and are compared with the experimental results of specific heat and neutron diffraction. The small total energy differences between the ferromagnetic (FM) and antiferromagnetic (AFM) configuration of ${\mathrm{CoTa}}_{2}{\mathrm{O}}_{6}$ shows that competing magnetic ground states exist, with the possibility of transition from FM to AFM phase at low temperature. Our calculation further suggests the semiconducting behavior for ${\mathrm{CoTa}}_{2}{\mathrm{O}}_{6}$ with a band gap of $\ensuremath{\sim}0.41$ eV. The calculated magnetic anisotropy energy is $\ensuremath{\sim}2.5$ meV with its easy axis along the [100] (in-plane) direction. Studying the evolution of magnetism in ${\mathrm{Co}}_{1\ensuremath{-}x}{\mathrm{Mg}}_{x}{\mathrm{Ta}}_{2}{\mathrm{O}}_{6}$ ($x=0$, 0.1, 0.3, 0.5, 0.7, and 1), it is found that the sharp AFM transition exhibited by ${\mathrm{CoTa}}_{2}{\mathrm{O}}_{6}$ at ${T}_{N}=6.2$ K in its heat capacity vanishes with Mg dilution, indicating the obvious effect of weakening the superexchange pathways of Co. The current specific heat study reveals the robust nature of ${T}_{N}$ for ${\mathrm{CoTa}}_{2}{\mathrm{O}}_{6}$ in applied magnetic fields. Clear indication of short-range magnetism is obtained from the magnetic entropy, however, diffuse components are absent in neutron diffraction data. At ${T}_{N}, {\mathrm{CoTa}}_{2}{\mathrm{O}}_{6}$ enters a long-range ordered magnetic state which can be described using a propagation vector, ($\frac{1}{4}\frac{1}{4}0$). Upon Mg dilution at $x\ensuremath{\ge}0.1$, the long-range ordered magnetism is destroyed. The present results should motivate an investigation of magnetic excitations in this low-dimensional anisotropic magnet.

The cubic intermetallic compound Sm 3Co 4Ge 13 (space group P m 3 &macr, n ) possesses a cage-like structure composed of Ge and displays an antiferromagnetic transition at T N &asymp, 6 K in magnetization, M ( T ) , specific heat, C p ( T ) and in thermal conductivity, &kappa, ( T ). The magnetic transition at T N is observed to be robust against applied magnetic fields up to 9 T. From the analysis of specific heat, a Sommerfeld coefficient &gamma, = 80(2) mJ/mol-Sm K 2 is estimated. The magnetic entropy released at T N is estimated as lower than that of a doublet, R ln(2). A positive Seebeck coefficient is observed for the thermopower, S ( T ) . Photoemission spectroscopy reveals distinct electronic character of the near-E F valence band states arising out of Co( 3 d)-Sm( 4 f) hybridization and Sm( 4 f) electron correlation. The unusual field-independent features in magnetization, specific heat and electrical transport is an indication of the significant correlation between f and d wave functions.