Multiple magnetic phase transitions in CePd2In4

The metallic compound EuCo2P2 with the body-centered tetragonal ThCr2Si2 structure containing Eu spins 7/2 was previously shown from single-crystal neutron diffraction measurements to exhibit a helical antiferromagnetic (AFM) structure below TN = 66.5 K with the helix axis along the c axis and with the ordered moments aligned within the ab-plane. Here we report crystallography, electrical resistivity, heat capacity, magnetization and magnetic susceptibility measurements on single crystals of this compound. We demonstrate that EuCo2P2 is a model molecular-field helical Heisenberg antiferromagnet from comparisons of the anisotropic magnetic susceptibility chi, high-field magnetization and magnetic heat capacity of EuCo2P2 single crystals at temperature T < TN with the predictions of our recent formulation of molecular field theory. Values of the Heisenberg exchange interactions between the Eu spins are derived from the data. The low-T magnetic heat capacity ~ T^3 arising from spin-wave excitations with no anisotropy gap is calculated and found to be comparable to the lattice heat capacity. The density of states at the Fermi energy of EuCo2P2 and the related compound BaCo2P2 are found from the heat capacity data to be large, 10 and 16 states/eV per formula unit for EuCo2P2 and BaCo2P2, respectively. These values are enhanced by a factor of ~2.5 above those found from DFT electronic structure calculations for the two compounds. The calculations also find ferromagnetic Eu-Eu exchange interactions within the ab-plane and AFM interactions between nearest- and next-nearest planes, in agreement with the MFT analysis of chi{ab}(T < TN).

We report the synthesis and the magnetic properties of single crystalline CeRhAl$_4$Si$_2$ and CeIrAl$_4$Si$_2$ and their non magnetic La-analogs. The single crystals of these quaternary compounds were grown using Al-Si binary eutectic as flux. The anisotropic magnetic properties of the cerium compounds were explored in detail by means of magnetic susceptibility, isothermal magnetization, electrical resistivity, magnetoresistivity and heat capacity measurements. Both CeRhAl$_4$Si$_2$ and CeIrAl$_4$Si$_2$ undergo two antiferromagnetic transitions, first from the paramagnetic to an antiferromagnetic state at $T_{\rm N1}$~=~12.6~K and 15.5~K, followed by a second transition at lower temperatures $T_{\rm N2}$~=~9.4~K and 13.8~K, respectively. The paramagnetic susceptibility is highly anisotropic and its temperature dependence in the magnetically ordered state suggests the $c$-axis to be the relatively easy axis of magnetization. Concomitantly, isothermal magnetization at 2~K along the $c$-axis shows a sharp spin-flop transition accompanied by a sizeable hysteresis, while it varies nearly linearly with field along the [100] direction up to the highest field 14~T, of our measurement. The electrical resistivity provides evidence of the Kondo interaction in both compounds, inferred from its $-lnT$ behavior in the paramagnetic region. The heat capacity data confirm the bulk nature of the two magnetic transitions in each compound, and further confirm the presence of Kondo interaction by a reduced value of the entropy associated with the magnetic ordering. From the heat capacity data below 1~K, the coefficient of the linear term in the electronic heat capacity, $\gamma$, is inferred to be 195.6 and 49.4~mJ/mol K$^2$ in CeRhAl$_4$Si$_2$ and CeIrAl$_4$Si$_2$, respectively classifying these materials as moderate heavy fermion compounds.

The title compound is characterized by magnetic susceptibility, magnetization, heat capacity, electrical resistivity, and magnetoresistivity measurements.

Magnetic, thermal and electrical properties of Er 3Co studied on single crystals

Magnetic ordering and low-temperature thermodynamic properties of ErFe 2Ge 2

Measurements of heat capacity, electrical resistivity, hemispherical total emittance, and normal spectral emittance of niobium in the temperature range 1500 to 2700 K by a subsecond duration pulse heating technique are described. Results obtained on the above properties are reported and are compared with those in the literature. A sharp increase in heat capacity above 2000 K was observed. Electrical resistivity showed a negative departure from linearity in the curve of electrical resistivity against temperature. Estimated inaccuracy of measured properties is: 2 percent for heat capacity, 0.5 percent for electrical resistivity, and 3 percent for hemispherical total and normal spectral emittances.

Evidence of phase transitions in MoO2 single crystals

A polycrystalline sample of superconducting $\mathrm{ThI}{\mathrm{r}}_{3}$ was obtained by arc-melting Th and Ir metals. Powder x-ray diffraction revealed that the compound crystalizes in a rhombohedral crystal structure (R-3m, s.g. #166) with the lattice parameters: $a=5.3394(1)\phantom{\rule{0.16em}{0ex}}\AA{}$ and $c=26.4228(8)\phantom{\rule{0.16em}{0ex}}\AA{}$. Normal and superconducting states were studied by magnetic susceptibility, electrical resistivity, and heat capacity measurements. The results showed that $\mathrm{ThI}{\mathrm{r}}_{3}$ is a type-II superconductor (Ginzburg-Landau parameter $\ensuremath{\kappa}=38)$ with the critical temperature ${T}_{\mathrm{c}}=4.41\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. The heat capacity data yielded the Sommerfeld coefficient $\ensuremath{\gamma}=17.6\phantom{\rule{0.16em}{0ex}}\mathrm{mJ}/(\mathrm{mo}\mathrm{l}\phantom{\rule{0.16em}{0ex}}{\mathrm{K}}^{2})$ and the Debye temperature ${\mathrm{\ensuremath{\Theta}}}_{\mathrm{D}}=169\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. The ratio $\mathrm{\ensuremath{\Delta}}C/(\ensuremath{\gamma}{T}_{\mathrm{c}})=1.6$, where $\mathrm{\ensuremath{\Delta}}C$ stands for the specific heat jump at ${T}_{\mathrm{c}}$, and the electron--phonon coupling constant ${\ensuremath{\lambda}}_{e\ensuremath{-}p}=0.74$ suggest that $\mathrm{ThI}{\mathrm{r}}_{3}$ is a moderate-strength superconductor. The experimental studies were supplemented by band structure calculations, which indicated that the superconductivity in $\mathrm{ThI}{\mathrm{r}}_{3}$ is governed mainly by $5d$ states of iridium. The significantly smaller band-structure value of Sommerfeld coefficient as well as the experimentally observed quadratic temperature dependence of resistivity and enhanced magnetic susceptibility suggest the presence of electronic interactions in the system, which compete with superconductivity.

Simultaneous measurements of heat capacity, electric resistivity, and hemispherical total emittance of an alloy of niobium, tantalum, and tungsten in the range 1500 to 2800 K

Lanthanide ($Ln$) based $Ln\mathrm{SbTe}$ materials have garnered significant attention due to the rich interplay of long-range magnetic ordering and topological properties, driven by unique crystalline symmetry, $4f$ electron interactions, and pronounced spin-orbit coupling (SOC) effects. DySbTe, as a heavier lanthanide based member of the $Ln\mathrm{SbTe}$ family, stands out with its SOC and larger on-site interactions on its $4f$ electrons, which arise due to the heavier Dy element. Here, we present a comprehensive study on the low-temperature bulk physical properties and the electronic structure of DySbTe using magnetic susceptibility, heat capacity, and electrical resistivity measurements, along with high-resolution angle-resolved photoemission spectroscopy (ARPES), scanning tunneling microscopy and spectroscopy (STM/S), and density functional theory calculations. Our thermodynamic measurements revealed an antiferromagnetic ordering below ${T}_{\mathrm{N}}=7.45$ K and a subsequent magnetic phase transition at ${T}_{\mathrm{N}1}=7.15$ K. Our transport studies indicate a semimetallic behavior with unusual feature in the ordered state. Our ARPES measurements revealed a diamond-shaped Fermi pocket centered at the $\overline{\mathrm{\ensuremath{\Gamma}}}$ point, with band features that evolve distinctly across various binding energies. STM/S results indicate a minimum in the density of states at around 100 meV below the Fermi level, and ARPES measurements reveal a significant gap present around the $\overline{\mathrm{X}}$ point, differentiating DySbTe from other $Ln\mathrm{SbTe}$ compounds. These findings enhance our understanding of the SOC effects on the electronic structure and topological properties in the $Ln\mathrm{SbTe}$ family, highlighting DySbTe as a promising candidate for exploring the interplay between topology and magnetism.

A technique is described for the high-speed measurement of heat capacity, electrical resistivity, hemispherical total and normal spectral emittances of electrical conductors at high temperatures (above 1900 K) with millisecond resolution. Duration of an individual experiment, in which the specimen is heated from room temperature to close to its melting point, is less than one second. Temperature measurements are made with a high-speed photoelectric pyrometer. Quantities are recorded by a high-speed digital data acquisition system which has a resolution of approximately one part in 8000. Time resolution of the entire system is 0.4 ms. Results on the above properties of molybdenum in the temperature range 1900 to 2800 K are reported and are compared with those in the literature. Estimated inaccuracy of measured properties in the above temperature range is: 2 to 3 percent for heat capacity, 0.5 percent for electrical resistivity, 3 percent for hemispherical total emittance and 2 percent for normal spectral emittance.

When immersed in liquid 3He, the nanometer strands of aerogel are coated with a thin layer of solid 3He, forming a network of irregular nanotubes. Owing to its high purity and weak interactions, this system is ideal for studying fundamental processes. We report the first experiments on solid 3He in aerogel at ultralow temperatures, cooled by direct adiabatic demagnetization. Simultaneous nuclear magnetic susceptibility and heat capacity measurements indicate a magnetic phase transition.

A sample of erbium borocarbide ErB2C was synthesized from a stoichiometric mixture of erbium, boron, and pyrographite hydride. Temperature dependent magnetic susceptibility, heat capacity and lattice parameters of borocarbide at 2–300 K were experimentally investigated, the Raman spectrum was determined and analyzed. Sharp anomalies in the heat capacity and magnetic properties of ErB2C near T = 16.3 K, caused by the transition to the antiferromagnetic state, as well as diffuse anomalies at a higher temperature, caused by the effect of the crystal field (Schottky anomalies) were revealed. It was found that the magnetic phase transition does not cause measurable anomalies in the lattice parameters of borocarbide due to the weak coupling between the Er3+ ion subsystem and the B–C layers. Almost zero thermal expansion of erbium borocarbide in the basal plane (along a and b axes) (anisotropic invar effect) as well as an unusual character of the c-axis thermal expansion were observed. The first of these features is due to the high bonding energy in the B–C layers and the weak bond between the layers in the borocarbide crystal lattice. It was found that the anomalous expansion along the c axis is a consequence of the action of the crystal field. The splitting scheme for the ground level of Er3+ ions by crystal field was determined from the analysis of the Schottky anomaly of the heat capacity.

This is a continuation of our magnetothermodynamic study of a 3.912-cm-diam spherical single crystal of CuK2(SO4)2·6H2O. The magnetic moment and heat capacity have been measured over the range 0.5–4.2°K, with fields of 0, 0.5, 1.0, 2.5, 5, 10, 15, 25, 40, 65, and 90 kG directed along the γ magnetic axis. At 0.5°K the magnetic moment reached limiting values in the field range 45–90 kG. Mγ(limit) = Mγ(sat) + χγ(dia) H = 5782.3−2.45 × 10−4H G·cm3/mole,where − 2.45 × 10−4 is the molal diamagnetic susceptibility, and 5782 is the molal saturation value of the temperature-dependent paramagnetic system. Thus, gγ = 2.071. The heat capacities at 90, 65, and 40 kG approached zero below 1°K, thus giving a common zero reference for the entropy of the lattice and electron systems. The heat required to remove quanta of h / 2π from the saturated condition was slightly larger than the magnetic work gβH as expected for a ferromagnetic system. No evidence of hysteresis was observed at temperatures above 0.5°K. Temperature-field measurements on 31 isentropes, which connected the isoerstedic heat capacity series, evaluated the entropy over the experimental range. The total electronic entropy was found to be 1.379 gibbs/mole compared to the expected R ln2 = 1.3775 gibbs/mole. Smoothed values of the heat capacity, entropy, magnetic moment, enthalpy, internal energy, differential isothermal magnetic susceptibility, differential isoerstedic temperature co-efficient of magnetic moment, and the isothermal work of magnetization are tabulated.

Analysis of structural and magnetic phase transition behaviors of La 1− xSr xCrO 3 by measurement of heat capacity with thermal relaxation technique