The low-temperature normal-state specific heat and resistivity curves of various nonmagnetic intermetallic compounds manifest an anomalous thermal evolution. Such an anomaly is exhibited as a break in the slope of the linearized C/T versus T^2 curve and as a drop in the R versus T curve, both at the same T_βγ. It is related, not to a thermodynamic phase transition, but to an anomaly in the density of states curves of the phonon or electron subsystems. On representing these two anomalies as additional Dirac-type delta functions, situated respectively at kB.θ_L (for lattice) and kB.θ_E (for electrons), an analytical expression for the total specific heat can be obtained. A least-square fit of this expression to experimental specific heat curves of various compounds reproduced satisfactorily all the features of the anomalous thermal evolution. The obtained fit parameters (in particular the Sommerfeld constant, γ_{0}, and Debye temperatures, θ_D, compare favorably with the reported values. Furthermore, the analysis shows that (i) (T_βγ) / (θ_D) = 0.2(1\pm1/\surd6) and (ii) γ_{0} {\propto} (θ_D)^2; both relations are in a reasonable agreement with the experimental results. Finally, this analysis (based on the above arguments) justifies the often-used procedure that treats the above anomaly in terms of either a thermal variation of θ_D or an additional Einstein mode.
We present a tutorial on the principles of crystal growth of intermetallic and oxide compounds from molten solutions, with an emphasis on the fundamental principles governing the underlying phase equilibria and phase diagrams of multicomponent systems.
Pauling had proposed that charge is transferred from the more electronegative atom to the less electronegative one during metallic alloying. An expression has recently been derived for the energy of the unlike atom-pair bond using that concept. In this paper, Pauling's view is further supported by showing that the electronegativity and valence differences between unlike atoms in binary metallic alloys are of the required magnitude and direction so as to bring the metallic radii ratio R_A/R_B by charge transfer to a value r_A/r_B for ideal packing in an intermetallic compound. It is also demons…
We present an investigation on the intermetallic compound formed by HoCuBi which has a monoclinic crystalline P2 structure with lattice parameters; a = 9:8012(26)A, b = 6:0647(6)A, c = 6:1663(13)A. In this report we performed an extensive analysis of the magnetic characteristics, specific heat at low temperature mainly close to the region of the observed antiferromagnetic transition with Neel temperature about 7 K, and to the field induced spin-crossover; the metamagnetic transition typically observed in antiferromagnetic systems by measurements of M-H, (Magnetization - Magnetic Field) at low …
We explore the stability of structure exhibiting hybridization gaps across a broad range of binary and ternary intermetallic compositions by means of band structure and total energy calculations. This search reveals previously unknown metal-based insulators, some with large gaps exceeding 1 eV, such as Al2Fe and Al4IrRe. We confirm large gaps using a hybrid density functional including exact exchange, and predict a gap of 2.2 eV for AlMnSi in the Pearson type tP6 structure, which is a chemically ordered ternary variant of the prototype MoSi2 (Pearson type tI6) structure.
Magnetism of the binary intermetallic compound MnGa$_4$ is re-investigated. Band-structure calculations predict antiferromagnetic behavior in contrast to Pauli paramagnetism reported previously. Magnetic susceptibility measurements on single crystals indeed reveal an antiferromagnetic transition at $T_N=393$ K. Neutron powder diffraction and $^{69,71}$Ga nuclear quadrupole resonance spectroscopy show collinear antiferromagnetic order with magnetic moments alligned along the [111] direction of the cubic unit cell. The magnetic moment of 0.80(3)$μ_B$ at 1.5 K extracted from the neutron data is i…
High-pressure powder x-ray diffraction experiments have revealed that sodium and gold react at room temperature and form new Na-Au intermetallic compounds under high pressure. We have identified four intermetallic phases up to 60 GPa. The first phase (phase I) is the known Na2Au with the tetragonal CuAl2-type structure. It changed to the second phase (phase II) at about 0.8 GPa, which has the composition Na3Au with the trigonal Cu3As-type or hexagonal Cu3P-type structure. Phase II further transformed to phase III at 3.6 GPa. Phase III has the same composition Na3Au with the cubic BiF3-type str…
The influence of pressure on the structural and elastic properties of ScM (M = Rh, Cu, Ag, Hg) compounds has been performed by using ab initio approach pseudopotential plane- wave method based on the density functional theory within the generalized gradient approximation (GGA). The optical properties have been investigated under zero pressure. It is found that the optimized lattice parameters for all metals are in good agreement with the experimental data and other available theoretical values.
Magnetic properties of the intermetallic compound NdCo$_2$Si$_2$ are investigated by using the Monte Carlo simulation (MCs) under Metropolis algorithm. The magnetism of the compound is caused by the existence of the rare earth (Nd3+) ions with a magnetic moment taking the value 2.7 muB. Firstly, the ground state phase diagrams are presented and discussed in different planes corresponding to different physical parameters of the system. The stable phases are explored for different configurations of the Hamiltonian of the system. These stable phases are determined by the minimal energies. For non…
Using the density functional theory (DFT) formulated within the framework of the plane-wave basis projector augmented wave (PAW) method, the temperature-dependent elastic properties of MgRE (RE=Y, Dy, Pr, Sc, Tb) intermetallics with B2-type structure are presented from first-principles. Our calculations are based on the fact that the elastic moduli as a function of temperature mainly results from thermal expansion. The comparison between the predicted results and the available experimental data for a benchmark material NiAl provides good agreements. At $T=0K$, our calculated values of lattice …
The structural electronic and optical properties of intermetallic compound MgRh were investigated by using the ab-initio technique from CASTEP code. In this study we have carried out the pseudo-potential plane-wave (PP-PW) method based on the density functional theory (DFT), within the generalized gradient approximation (GGA). Our calculated structural parameters and corresponding graphical values fit with other previous available experimental data and other theoretical observations. The calculated electronic band structure reveals metallic conductivity and the major contribution comes from Rh…
The ternary intermetallic RTX compounds (R = rare earth, T = transitional metal, X = p-block metal) have been investigated extensively in the past few decades due to their interesting physical properties. Recently, much attention has been paid to the magnetocaloric effect (MCE) of these RTX compounds, especially the ones with heavy rare-earth, for their potential application in low temperature magnetic refrigeration. In this paper, we review the MCE of RTSi and RTAl systems with R = Gd~Tm, T = Fe~Cu and Pd, which are widely investigated in recent years. It is found that these RTX compounds exh…
We have synthesized the intermetallic YPrFe17 compound by arc-melting. X-ray and neutron powder diffraction show that the crystal structure is rhombohedral with View the MathML source space group (Th2Zn17-type). The investigated compound exhibits a broad isothermal magnetic entropy change ΔSM(T) associated with the ferro-to-paramagnetic phase transition (TC \approx 290 K). The |ΔSM| (\approx 2.3 J kg-1 K-1) and the relative cooling power (\approx 100 J kg-1) have been calculated for applied magnetic field changes up to 1.5 T. A single master curve for ΔSM under different values of the magnetic…
The phonon and thermodynamic properties of rare-earth-aluminum intermetallics AlRE (RE=Y, Gd, Pr, Yb) with B2-type structure are investigated by performing density functional theory and density functional perturbation theory within the quasiharmonic approximation. The phonon spectra and phonon density of states, including the phonon partial density of states and total density of states, have been discussed. Our results demonstrate that the density of states is mostly composed of Al states at the high frequency. The temperature dependence of various quantities such as the thermal expansions, th…
we present the temperature-dependent elastic constants of two ductile rare-earth intermetallic compounds YAg and YCu with CsCl-type B2 structure by using a first-principles approach. The elastic moduli as a function of temperature are predicted from the combination of static volumedependent elastic constants obtained by the first-principles total-energy method with density functional theory and the thermal expansion obtained by the first-principles phonon calculations with density-functional perturbation theory. The comparison between our calculated results and the available experimental data …
A binary intermetallic compound Er5Pd2 has been investigated using dc and ac magnetic susceptibilities, magnetic memory effect, isothermal magnetization, non-linear dc susceptibility, heat capacity and magnetocaloric effect studies. Interestingly, even though the compound does not show geometrical frustration it undergoes glassy magnetic phase transition below 17.2 K. Investigation of dc magnetisation and heat capacity data divulged absence of long-ranged magnetic ordering. Through magnetic memory effect, time dependent magnetization and ac susceptibility studies it was revealed that the compo…
High-entropy intermetallic compounds (HEICs) were fabricated by mechanical alloying and spark plasma sintering to fill a knowledge gap between the traditional high-entropy alloys (HEAs) and emerging high-entropy ceramics (HECs). Notably, several four- or five-component equimolar aluminides, such as the B2-phase (Fe1/5Co1/5Ni1/5Mn1/5Cu1/5)Al, have been made into single-phase HEICs for the first time. Thermodynamic modeling and a reversible, temperature-dependent, phase-stability experiment suggest that such B2-phase HEICs are entropy-stabilized phases. The structure of these HEICs resembles tha…
Theoretical investigation of structural, elastic, electronic and bonding properties of A-15 Nb-based intermetallic compounds Nb3B (B = Pt, Os) have been performed using first principles calculations based on the density functional theory (DFT). Optimized cell parameters are found to be in good agreement with available experimental and theoretical results. The elastic constants at zero pressure and temperature are calculated and the anisotropic behaviors of the compounds are studied. Both the compounds are mechanically stable and ductile in nature. Other elastic properties such as Pugh's ratio,…
Time-differential perturbed angular correlation (TDPAC) measurements have been carried out in stoichiometric ZrNi$_3$ and HfNi$_3$ intermetallic compounds using $^{181}$Ta probe in the temperature range 77-1073 K considering the immense technological applications of Zr-Ni and Hf-Ni intermetallic compounds. In ZrNi$_3$, four components due to the production of Zr$_2$Ni$_7$, Zr$_8$Ni$_{21}$, Zr$_7$Ni$_{10}$ and ZrNi$_3$ have been found at room temperature. The HfNi$_3$ sample produces five electric quadrupole interaction frequencies at room temperature. The phase HfNi$_3$ is strongly produced in…
The magnetocaloric effect (MCE) in many rare earth (RE) based intermetallic compounds has been extensively investigated during last two decades, not only due to their potential applications for magnetic refrigeration but also for better understanding of the fundamental problems of the materials. This paper reviews our recent progress of magnetic properties and MCE in some binary or ternary intermetallic compounds of RE with low boiling point metal(s) (Zn, Mg, and Cd). Some of them are exhibiting promising MCE properties which make them also attractive for low temperature magnetic refrigeration…
Single crystals of a new ternary aluminide ErV$_2$Al$_{20}$ were grown using a self-flux method. The crystal structure was determined by powder X-ray diffraction measurements and Rietveld refinement, and physical properties were studied by means of electrical resistivity, magnetic susceptibility and specific heat measurements. These measurements reveal that ErV$_2$Al$_{20}$ is a Curie-Weiss paramagnet down to 1.95 K with an effective magnetic moment $μ_{eff}$ = 9.27(1) $μ_B$ and Curie-Weiss temperature $Θ_{CW}$ = -0.55(4) K. The heat capacity measurements show a broad anomaly at low temperatur…
Surface alloying is a straightforward route to control and modify the structure and electronic properties of surfaces. Here, We present a systematical study on the structural and electronic properties of three novel rare earth-based intermetallic compounds, namely ReAu2 (Re = Tb, Ho, and Er), on Au(111) via directly depositing rare-earth metals onto the hot Au(111) surface. Scanning tunneling microscopy/spectroscopy measurements reveal the very similar atomic structures and electronic properties, e.g. electronic states, and surface work functions, for all these intermetallic compound systems d…
Intermetallic compounds are key materials for energy transition as they form reversible hydrides that can be used for solid state hydrogen storage or as anodes in batteries. ABy compounds (A = Rare Earth (RE); B = transition metal; 2 < y < 5) are good candidates to fulfill the required properties for practical applications. They can be described as stacking of AB5 and AB2 sub-units along the c crystallographic axis. The latter sub-unit brings a larger capacity, while the former one provides a better cycling stability. However, ABy binaries do not show good enough properties for applications. U…
Numerous technological applications of Ni-based Zr and Hf intermetallic alloys promoted comprehensive studies in Zr$_8$Ni$_{21}$ and Hf$_8$Ni$_{21}$ by perturbed angular correlation (PAC) spectroscopy, which were not studied earlier until this report. The different phases produced in the samples have been identified by PAC and X-ray diffraction (XRD) measurements. Using $^{181}$Hf probe, two non-equivalent Zr/Hf sites have been observed in both Zr$_8$Ni$_{21}$ and Hf$_8$Ni$_{21}$ compounds. From present PAC measurements in Zr$_8$Ni$_{21}$, a component due to the production of Zr$_7$Ni$_{10}$ b…
C14 Nb(Fe89.4Al10.6)2 Laves phase intermetallic compound was investigated by DC magnetization (M) measurements performed in the temperature (T) interval of 20 to 175 K,under an applied magnetic field (H) ranging between 50 and 1250 Oe. Magnetization curves were recorded in the field-cooled (FC) and in the zero-field-cooled (ZFC) modes. They clearly showed an irreversible character that vanished at H=1250 Oe. Both magnetization curves exhibited well-defined peaks around T_N =72.3 K whose positions were H-independent, so they were identified as the compound's Néel temperature. The existence of i…
We report the development of a versatile material preparation chain for intermetallic compounds that focuses on the realization of a high-purity growth environment. The preparation chain comprises of an argon glovebox, an inductively heated horizontal cold boat furnace, an arc melting furnace, an inductively heated rod casting furnace, an optically heated floating-zone furnace, a resistively heated annealing furnace, and an inductively heated annealing furnace. The cold boat furnace and the arc melting furnace may be loaded from the glovebox by means of a load-lock permitting to synthesize com…
We study the magnetic susceptibility, magnetization, resistivity and thermal conductivity of intermetallic HoAgGe single crystals at low temperatures and in magnetic fields along the $a$ and $c$ axis, while the electric and heat currents are along the $c$ axis. The magnetization curves show a series of metamagnetic transitions and small hysteresis at low field for $B \parallel a$, and a weak metamagnetic transition for $B \parallel c$, respectively. Both the magnetic susceptibility and $ρ(T)$ curve show anomalies at the antiferromagnetic transition ($T\rm_N \sim$ 11.3 K) and spin reorientation…
Intermetallic compounds possess unique atomic arrangements that often lead to exceptional material properties, but their extreme brittleness usually causes fracture at a limited strain of less than 1% and prevents their practical use. Therefore, it is critical for them to exhibit either plasticity or some form of structural transition to absorb and release a sufficient amount of mechanical energy before failure occurs. This study reports that the ThCr2Si2-structured intermetallic compound (CaFe2As2) and a hybrid of its structure (CaKFe4As4) with 2 μm in diameter and 6 μm in height can exhibit …
Here, we demonstrate two reliable routes for the fabrication of armchair-edge graphene nanoribbons (GNRs) on TbAu2/Au(111), belonging to a class of two-dimensional ferromagnetic rare earth-gold intermetallic compounds. On-surface synthesis directly on TbAu2 leads to the formation of GNRs, which are short and interconnected with each other. In contrast, the intercalation approach - on-surface synthesis of GNRs directly on Au(111) followed by rare earth intercalation - yields GNRs on TbAu2/Au(111), where both the ribbons and TbAu2 are of high quality comparable with those directly grown on clean…
The present study investigates the partial substitutions of Mn and Cu for Fe in the TiFe-system to gain better understanding of the role of elemental substitution on its hydrogen storage properties. The TiFe0.88-xMn0.02Cux (x = 0, 0.02, 0.04) compositions were studied. From X-Ray Diffraction (XRD) and Electron Probe Micro-Analysis (EPMA), it was found that all alloys are multi-phase, with TiFe as a major phase, together with \b{eta}-Ti and Ti4Fe2O-type as secondary precipitates, of all them containing also Mn and Cu. Increasing the Cu content augments the secondary phase amounts. Low quantity …
We investigate the electronic structure and several properties, and topological character, of the cubic time-reversal invariant intermetallic compounds PbPd$_3$ and SnPd$_3$ using density functional theory based methods. These compounds have a dispersionless band along the $Γ-X$ line, forming the top of the Pd $4d$ bands and lying within a few meV of the Fermi level $E_F$. Effects of the flat band on transport and optical properties have been inspected by varying the doping concentration treated with the virtual crystal approximation for substitution on the Pb site. In the absence of spin-orbi…
Magnetocaloric effect in Mn4FeGe3-xSix compounds has been studied by dc magnetization measurements. For the parent compound Mn4FeGe3, the paramagnetic to ferromagnetic transition temperature TC is above room temperature (320 K), which initially remains constant for small Si substitution at the Ge site and then decreases marginally with an increase in Si concentration. A large change in magnetic entropy at the TC, under a magnetic field variation of 50 kOe, with typical values of 5.9, 6.5, 5.9 and 4.4 J kg-1 K-1 for x = 0, 0.2, 0.6, and 1 samples, respectively, along with a broad operating temp…
Neutron scattering studies have been carried out on polycrystalline samples of a series of rare earth intermetallic compounds RCuAs$_2$ (R = Pr, Nd, Dy, Tb, Ho and Yb) as a function of temperature to determine the magnetic structures and the order parameters. These compounds crystallize in the ZrCuSi$_2$ type structure, which is similar to that of the RFeAsO (space group P4/nmm) class of iron-based superconductors. PrCuAs$_2$ develops commensurate magnetic order with K = (0, 0, 0.5) below T$_N$ = 6.4 (2) K, with the ordered moments pointing along the c-axis. The irreducible representation anal…
The discovery of the 1144-phase, e.g. CaKFe$_4$As$_4$, creates opportunities to build novel intermetallics with alternative stacking of two parent compounds. Here we formalize the idea by defining a class of bulk crystalline solids with $A$-$B$ stacking (including 1144-phases and beyond), which is a generalization of hetero-structures from few-layer or thin-film semi-conductors to bulk intermetallics. Theoretically, four families of phosphides \textit{AB}(TM)$_4$P$_4$ (TM=Fe, Ru, Co, Ni) are investigated by first-principles calculations, wherein configurational, vibrational and electronic degr…
Iron and cobalt distannides \ce{MSn2} (M = Fe, Co) are regarded as a promising conversion-type anode material for lithium- and sodium-ion batteries, but their properties are not well understood. In this work, we report a first-principles study of alkali metal (A = Li, Na) substitutional effect on the structural, mechanical, lattice vibrational, electronic and defect properties of these distannides. Special attention is paid to systematic comparison between \ce{FeSn2} and \ce{CoSn2}. Our calculations reveal that M/A substitution induces a lattice expansion and decrease of elastic constants, whi…
Low temperature scanning tunneling spectroscopy of HfNiSn shows a V^m(m < 1) zero bias anomaly around the Fermi level. This local density of states with a fractional power law shape is well known to be a consequence of electronic correlations. For comparison, we have also measured the tunneling conductances of other half-Heusler compounds with 18 valence electrons. ZrNiPb shows a metal-like local density of states, whereas ZrCoSb and NbFeSb show a linear and V^2 anomaly. One interpretation of these anomalies is that a correlation gap is opening in these compounds. By analyzing the magnetoresis…
Structural, elastic and electronic band structure properties of A-15 type Nb-based intermetallic compounds Nb3B (B = Os, Pt, Au) have been revisited using first principles calculations based on the density functional theory (DFT). All these show excellent agreement with previous reports. More importantly, electronic bonding, charge density distribution and Fermi surface features have been studied in detail for the first time. Vickers hardness of these compounds is also studied. The Fermi surfaces of Nb3B contain both hole- and electron-like sheets, the features of which change systematically a…
{Spin polarization tuning in Mn$_{x}$Fe$_{1-x}$Ge$_{3}$
在实验上，最近已经显示金属间化合物Mn $_{4}$ FeGe $_{3}$与Mn $_{5}$ Ge $_{3}$母体化合物相比表现出增强的磁性和自旋极化。本{ \em ab-initio}研究的重点是铁取代的电子和磁性的化合物的影响。我们的计算结果表明，费米面的掺杂化合物的变化是显着的，并提供了增强的自旋极化观察到的解释。最后，我们表明，它确实是可能的，以调整自旋极化的程度后，Fe掺杂，从而使Mn $_{1-x}$ Fe $_{x}$ Ge $_{3}$金属间合金非常有前途的未来自旋电子学应用。
Two types of solute-solute interactions are investigated in this work. Quadrupole interactions caused by nearby Ag-solute atoms were measured at nuclei of 111In/Cd solute probe atoms in the binary compound GdAl2 using the method of perturbed angular correlation of gamma rays (PAC). Locations of In-probes and Ag-solutes on both Gd- and Al-sublattices were identified by comparing site fractions in Gd-poor and Gd-rich GdAl2(Ag) samples. Interaction enthalpies between solute-atom pairs were determined from temperature dependences of observed site fractions. Repulsive interactions were observed for…
This work has been presented by RJCV to obtain his PhD degree at Fluminense Federal University, in March of 2017. We focused on the synthesis of compounds and then on their magneto-strucutral characterization; mainly due to the interplay of these physical properties. We have prepared intermetallic alloys (including Heusler alloys) and perovskite oxides (manganites and cobaltites); in bulk and nanoparticles. A thorough analysis of the influence of the morphology and crystal structure on the magnetic properties of these compounds is addressed.
Spin ices are exotic phases of matter characterized by frustrated spins obeying local ice rules, in analogy with the electric dipoles in water ice. In two dimensions, one can similarly define ice rules for in-plane Ising-like spins arranged on a kagome lattice. These ice rules require each triangle plaquette to have a single monopole, and can lead to various unique orders and excitations. Using experimental and theoretical approaches including magnetometry, thermodynamic measurements, neutron scattering and Monte Carlo simulations, we establish HoAgGe as a crystalline (i.e. non-artificial) sys…
Magnetic and magnetoresistance behavior of Tb7Rh3, an intermetallic compound with a negative temperature coefficient of electrical resistivity in the paramagnetic state, and Paramagnetic Giant Magnetoresistance Phenomenon
直流磁化，电和磁电阻和热容量测量（2-300 K）的结果Tb 7 Rh 3，在Th 7 Fe 3型六方结构结晶，报告。在这种化合物中，磁有序集在约90 K，在低温下具有额外的转变，并且电阻率（R）的温度系数dR/dT在顺磁状态下在很宽的温度范围内为负。磁化结果表明，该化合物在磁场-温度相图中具有丰富的特征。主要强调的一点是，顺磁状态下的dR/dT的符号可以通过施加磁场而逐渐改变。结果，除了在磁有序状态下的巨磁阻行为之外，磁阻（MR）的幅度即使在室温附近（远高于磁有序温度）也相当大。与该系列的其他重稀土元素类似，这类化合物可以被归类为顺磁性巨磁阻系统。一种新的理论方法是必要的，以了解这一现象。
