Showing papers by "M. B. Maple published in 2005"
TL;DR: In this paper, the x-ray diffraction, specific-heat, electrical resistivity, and magnetization measurements were used to characterize a single-crystal compound with lattice parameter $a=9.
Abstract: The filled skutterudite compound $\mathrm{Sm}{\mathrm{Os}}_{4}{\mathrm{Sb}}_{12}$ was prepared in single-crystal form and characterized using x-ray diffraction, specific-heat, electrical resistivity, and magnetization measurements. The $\mathrm{Sm}{\mathrm{Os}}_{4}{\mathrm{Sb}}_{12}$ crystals have the $\mathrm{La}{\mathrm{Fe}}_{4}{\mathrm{P}}_{12}$-type structure with lattice parameter $a=9.3085\phantom{\rule{0.3em}{0ex}}\mathrm{\AA{}}$. Specific-heat measurements indicate a large electronic specific-heat coefficient of $\ensuremath{\approx}880\phantom{\rule{0.3em}{0ex}}\mathrm{mJ}∕\mathrm{mol}\phantom{\rule{0.2em}{0ex}}{\mathrm{K}}^{2}$, from which an enhanced effective mass ${m}^{*}\ensuremath{\approx}170{m}_{e}$ is estimated. The specific-heat data also suggest crystalline electric field (CEF) splitting of the ${\mathrm{Sm}}^{3+}J=5∕2$ multiplet into a ${\ensuremath{\Gamma}}_{7}$ doublet ground state and a ${\ensuremath{\Gamma}}_{8}$ quartet excited state separated by $\ensuremath{\sim}37\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. Electrical resistivity $\ensuremath{\rho}(T)$ measurements reveal a decrease in $\ensuremath{\rho}(T)$ below $\ensuremath{\sim}50\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ that is consistent with CEF splitting of $\ensuremath{\sim}33\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ between a ${\ensuremath{\Gamma}}_{7}$ doublet ground state and ${\ensuremath{\Gamma}}_{8}$ quartet excited state. Specific-heat and magnetic susceptibility measurements display a possible weak ferromagnetic transition at $\ensuremath{\sim}2.6\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, which could be an intrinsic property of $\mathrm{Sm}{\mathrm{Os}}_{4}{\mathrm{Sb}}_{12}$ or possibly due to an unknown impurity phase.
96 citations
Journal Article•
77 citations
TL;DR: The deviation of the physical properties of URu2-xRexSi2 from Fermi-liquid behavior is most pronounced at the ferromagnetic quantum critical point, and the NFL behavior found in theFerromagnetic phase may be consistent with the Griffiths-McCoy phase model.
Abstract: The ${\mathrm{U}\mathrm{R}\mathrm{u}}_{2\ensuremath{-}x}{\mathrm{R}\mathrm{e}}_{x}{\mathrm{S}\mathrm{i}}_{2}$ system exhibits ferromagnetic order for Re concentrations $0.3lx\ensuremath{\le}1.0$. Non-Fermi-liquid (NFL) behavior is observed in the specific heat for $0.15\ensuremath{\le}x\ensuremath{\le}0.6$ [$C/T\ensuremath{\propto}\ensuremath{-}\mathrm{ln} T$ (or ${T}^{\ensuremath{-}0.1}$)], and also in the power-law $T$ dependence of the electrical resistivity [$\ensuremath{\rho}(T)\ensuremath{\propto}{T}^{n}$] with $nl2$ for $0.15\ensuremath{\le}xl0.8$, at low $T$, providing strong evidence that the NFL behavior persists within the ferromagnetic phase. Furthermore, the deviation of the physical properties of ${\mathrm{U}\mathrm{R}\mathrm{u}}_{2\ensuremath{-}x}{\mathrm{R}\mathrm{e}}_{x}{\mathrm{S}\mathrm{i}}_{2}$ from Fermi-liquid behavior is most pronounced at the ferromagnetic quantum critical point, and the NFL behavior found in the ferromagnetic phase may be consistent with the Griffiths-McCoy phase model.
60 citations
TL;DR: In this paper, the authors investigated the electrical resistivity, magnetization, and specific heat properties of the filled-skutterudite compound O(nd) with a lattice parameter of $9.3m and showed that it conforms to mean field ferromagnetism.
Abstract: Single crystals of the filled-skutterudite compound $\mathrm{Nd}{\mathrm{Os}}_{4}{\mathrm{Sb}}_{12}$ have been investigated by means of electrical resistivity, magnetization, and specific heat measurements. The $\mathrm{Nd}{\mathrm{Os}}_{4}{\mathrm{Sb}}_{12}$ crystals have the $\mathrm{La}{\mathrm{Fe}}_{4}{\mathrm{P}}_{12}$-type cubic structure with a lattice parameter of $9.3\phantom{\rule{0.3em}{0ex}}\mathrm{\AA{}}$. Possible heavy-fermion behavior is inferred from specific heat measurements, which reveal a large electronic specific heat coefficient $\ensuremath{\gamma}\ensuremath{\approx}520\phantom{\rule{0.3em}{0ex}}\mathrm{mJ}∕\mathrm{mol}\phantom{\rule{0.2em}{0ex}}{\mathrm{K}}^{2}$, corresponding to an effective mass ${m}^{*}\ensuremath{\approx}98{m}_{e}$. Features related to a ferromagnetic transition at $\ensuremath{\sim}0.9\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ can be observed in electrical resistivity, magnetization, and specific heat. Conventional Arrott-plot analysis indicates that $\mathrm{Nd}{\mathrm{Os}}_{4}{\mathrm{Sb}}_{12}$ conforms to mean-field ferromagnetism.
55 citations
TL;DR: In this article, the authors observed an unexpected enhancement of the lower critical field H(c1)(T) and the critical current I(c)(T), in the filled skutterudite heavy fermion superconductor PrOs(4)Sb(12) near T/T(c) approximately 0.3.
Abstract: We have observed an unexpected enhancement of the lower critical field H(c1)(T) and the critical current I(c)(T) deep in the superconducting state below T approximately 0.6 K (T/T(c) approximately 0.3) in the filled skutterudite heavy fermion superconductor PrOs(4)Sb(12). From a comparison of the behavior of H(c1)(T) with that of the heavy fermion superconductors U(1-x)Th(x)Be(13) and UPt(3), we speculate that the enhancement of H(c1)(T) and I(c)(T) in PrOs(4)Sb(12) reflects a transition into another superconducting phase that occurs below T/T(c) approximately 0.3. An examination of the literature reveals unexplained anomalies in other physical properties of PrOs(4)Sb(12) near T/T(c) approximately 0.3 that correlate with the features we have observed in H(c1)(T) and I(c)(T).
47 citations
Journal Article•
TL;DR: An examination of the literature reveals unexplained anomalies in other physical properties of PrOs(4)Sb(12) near T/T(c) approximately 0.3 that correlate with the features the authors have observed in H(c1)(T) and I(c)(T).
41 citations
TL;DR: It is demonstrated that Yb(14)MnSb(11) is the first ferromagnetic Kondo lattice compound in the underscreened limit and a scenario whereby the combination of Kondo and Jahn-Teller effects provides a consistent explanation of both transport and optical data is proposed.
Abstract: We report on a comprehensive optical, transport, and thermodynamic study of the Zintl compound ${\mathrm{Yb}}_{14}{\mathrm{MnSb}}_{11}$, demonstrating that it is the first ferromagnetic Kondo lattice compound in the underscreened limit. We propose a scenario whereby the combination of Kondo and Jahn-Teller effects provides a consistent explanation of both transport and optical data.
36 citations
TL;DR: In this article, specific heat measurements were made on single crystals of the superconducting filled skutterudite series and the results showed that superconductivity was observed for all values of the Ru$ concentration with transition temperatures consistent with previous experiments, confirming a minimum in ${T}_{c}$ at $x=0.6.
Abstract: Specific heat $C(T)$ measurements were made on single crystals of the superconducting filled skutterudite series $\mathrm{Pr}{({\mathrm{Os}}_{1\ensuremath{-}x}{\mathrm{Ru}}_{x})}_{4}{\mathrm{Sb}}_{12}$ down to $0.6\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. Crystalline electric field fits in the normal state produced parameters which were in agreement with previous measurements. Bulk superconductivity was observed for all values of the $\mathrm{Ru}$ concentration $x$ with transition temperatures consistent with previous experiments, confirming a minimum in ${T}_{c}$ at $x=0.6$. The $C(T)$ data below ${T}_{c}$ appear to be more consistent with power-law behavior for $x=0$ $({\mathrm{PrOs}}_{4}{\mathrm{Sb}}_{12})$, and with exponential behavior for $0.05\ensuremath{\leqslant}x\ensuremath{\leqslant}0.2$. An enhanced electronic specific heat coefficient $\ensuremath{\gamma}$ was observed for $x\ensuremath{\leqslant}0.4$, further supporting $x\ensuremath{\simeq}0.6$ as a critical concentration where the physical properties abruptly change. Significant enhancement of $\ensuremath{\Delta}C∕{T}_{c}$ above the weak-coupling value was observed only for $x=0$ and 0.05.
33 citations
30 citations
TL;DR: It is argued that the observed non-Fermi-liquid behavior in these f-electron materials arises from the critical phenomena near a T=0 K phase transition, irrespective of the nature of the transition.
Abstract: We used inelastic neutron scattering to study magnetic excitations of Sc1-xUxPd3 for U concentrations (x=0.25, 0.35) near the spin glass quantum critical point (QCP). The excitations are spatially incoherent, broad in energy (E=variant Planck's over 2piomega), and follow omega/T scaling at all wave vectors investigated. Since similar omega/T scaling has been observed for UCu5-xPdx and CeCu6-xAux near the antiferromagnetic QCP, we argue that the observed non-Fermi-liquid behavior in these f-electron materials arises from the critical phenomena near a T=0 K phase transition, irrespective of the nature of the transition.
23 citations
TL;DR: In this paper, the existence of a quantum critical point at critical pressures was investigated by means of specific heat measurements at zero pressure and electrical resistivity measurements under nearly hydrostatic pressure up to $28\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ and the normalized residual resistivity
Abstract: Single crystals of $\mathrm{Ce}{\mathrm{Rh}}_{1\ensuremath{-}x}{\mathrm{Co}}_{x}{\mathrm{In}}_{5}$ have been investigated by means of specific heat measurements at zero pressure and electrical resistivity measurements under nearly hydrostatic pressure up to $28\phantom{\rule{0.3em}{0ex}}\mathrm{kbar}$. Specific heat measurements for samples of $\mathrm{Ce}{\mathrm{Rh}}_{1\ensuremath{-}x}{\mathrm{Co}}_{x}{\mathrm{In}}_{5}$ with cobalt concentrations of $x=0.65$, 0.71, 0.77, 0.87, and 0.93 confirm the existence of antiferromagnetism for $0\ensuremath{\leqslant}x\ensuremath{\leqslant}0.7$ and suggest the existence of a quantum critical point at ${x}_{c}\ensuremath{\sim}0.75$. Entropy versus $x$ isotherms below $\ensuremath{\sim}5\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ and the normalized residual resistivity $\ensuremath{\rho}(0\phantom{\rule{0.3em}{0ex}}\mathrm{K})∕\ensuremath{\rho}(290\phantom{\rule{0.3em}{0ex}}\mathrm{K})$ versus $x$ curve both display maxima near ${x}_{c}\ensuremath{\sim}0.75$, suggesting further evidence for the existence and location of the quantum critical point. Electrical resistivity measurements under pressure for samples with $x=0.1$, 0.2, 0.4, and 0.6 reveal antiferromagnetism, pressure-induced superconductivity, and the coexistence of antiferromagnetism and superconductivity. Normalized residual resistivity $\ensuremath{\rho}(0\phantom{\rule{0.3em}{0ex}}\mathrm{K})∕\ensuremath{\rho}(290\phantom{\rule{0.3em}{0ex}}\mathrm{K})$ versus pressure $P$ curves and the evolution of the power-law exponent $n$ favor the existence of quantum critical points at critical pressures ${P}_{c}\ensuremath{\sim}23\phantom{\rule{0.3em}{0ex}}\mathrm{kbar}$, $\ensuremath{\sim}21\phantom{\rule{0.3em}{0ex}}\mathrm{kbar}$, and $\ensuremath{\sim}7\phantom{\rule{0.3em}{0ex}}\mathrm{kbar}$ for samples with $x=0.1$, 0.2, and 0.4, respectively.
Journal Article•
TL;DR: The EXAFS data clearly show that a Ru displacement is associated with this metal-to-insulator (MI) phase transition in PrRu(4)P(12), and suggests that a slight rotation/displacement of relatively rigid RuP(6) octahedra leads to this small Ru displacement, which accompanies the MI transition at 62 K in Pr Ru(4]P( 12.
Abstract: Extended x-ray absorption fine structure (EXAFS) experiments have been carried out on ${\mathrm{P}\mathrm{r}\mathrm{R}\mathrm{u}}_{4}{\mathrm{P}}_{12}$ and ${\mathrm{P}\mathrm{r}\mathrm{O}\mathrm{s}}_{4}{\mathrm{P}}_{12}$ to study the metal-to-insulator (MI) phase transition in ${\mathrm{P}\mathrm{r}\mathrm{R}\mathrm{u}}_{4}{\mathrm{P}}_{12}$. No Pr displacement was observed across the MI transition temperature from the EXAFS data. Instead, our EXAFS data clearly show that a Ru displacement is associated with this MI transition. The very high Debye temperature for the Ru-P bond (${\ensuremath{\Theta}}_{D}=690\text{ }\mathrm{K}$) suggests that a slight rotation/displacement of relatively rigid ${\mathrm{R}\mathrm{u}\mathrm{P}}_{6}$ octahedra leads to this small Ru displacement, which accompanies the MI transition at 62 K in ${\mathrm{P}\mathrm{r}\mathrm{R}\mathrm{u}}_{4}{\mathrm{P}}_{12}$.
TL;DR: In this article, a detailed study on the transport properties of as-cast and heat treated material UCu$_4$Pd is presented, and the authors find a pronounced sample dependence of the resistivity of the material.
Abstract: We present a detailed study on the (magneto)transport properties of as-cast and heat treated material UCu$_4$Pd. We find a pronounced sample dependence of the resistivity $\rho$ of as-cast samples, and reproduce the annealing dependence of $\rho$. In our study of the Hall effect we determine a metallic carrier density for all samples, and a temperature dependence of the Hall constant which is inconsistent with the Skew scattering prediction. The magnetoresistive response is very small and characteristic for spin disorder scattering, suggesting that overall the resistivity is controlled mostly by nonmagnetic scattering processes. We discuss possible sources for the temperature and field dependence of the transport properties, in particular with respect to quantum criticality and electronic localization effects.
TL;DR: In this paper, the angular dependence of in-plane magnetoresistivity of Y1−xPrxBa2Cu3O7− single crystals with 0.0 x 0.53 was investigated.
Abstract: We investigated in-plane angular magnetoresistivity ab / ab 0° below and above the zero-field critical temperature Tc0 of Y1−xPrxBa2Cu3O7− single crystals with 0.0 x 0.53. The angular dependence of in-plane magnetoresistivity shows three temperature regimes: a a low T regime which extends from below to above the critical temperature Tc0, up to an x-dependent temperature e.g., up to 1.15 Tc0 for x=0.46 , displaying a two-dimensional 2D scaling consistent with pancakelike excitation , b an intermediate T regime, corresponding to vortex line excitations, which extends up to T Tc0, and c a high T regime in which the quasiparticles dominate the dissipation. The constructed electronic phase diagram shows that T x departs from Tc0 x for x 0.20 and reaches a maximum at x=0.46.
TL;DR: In this article, the superconductivity of the filled skutterudite compounds Pr ( Os 1 - x Ru x ) 4 Sb 12, NdOs 4 S b 12, and SmOs 4 sb 12 is discussed.
Abstract: Recent measurements on the filled skutterudite compounds Pr ( Os 1 - x Ru x ) 4 Sb 12 , NdOs 4 Sb 12 , and SmOs 4 Sb 12 are discussed. Pr ( Os 1 - x Ru x ) 4 Sb 12 displays superconductivity for all values of x with a minimum at x = 0.6 , and only the compounds with x 0.6 display heavy fermion characteristics, suggesting a competition between the unconventional heavy fermion superconductivity of PrOs 4 Sb 12 and the BCS superconductivity of PrRu 4 Sb 12 . NdOs 4 Sb 12 is a heavy fermion ferromagnet, with a sharp transition observed at 1.0 K. SmOs 4 Sb 12 is also a heavy fermion material, and it may display weak ferromagnetic behavior below 2.6 K.
TL;DR: In this paper, the superconducting phase diagram of PrOs4Sb12 was deduced from the real part χ and the imaginary part of the AC susceptibility, where full diamagnetic shielding is observed below T c 2 only.
Abstract: We report the superconducting phase diagram of PrOs4Sb12 deduced from the real-part χ ′ and the imaginary part χ ″ of the AC susceptibility. The double transition at T c 1 = 1.85 K and T c 2 = 1.75 K seen in the specific heat may be related to features in χ ′ and χ ″ , where full diamagnetic shielding is observed below T c 2 only. As function of magnetic field the phase bounded by T c 2 displays features reminiscent of the peak effect.
TL;DR: In this article, the authors carried out 115In nuclear quadrupole resonance (NQR) measurements in CeCoIn 5 under pressure P. The results showed that the system locates just at the antiferromagnetic AF instability and the anisotropic superconductivity with line nodes appears.
Abstract: We have carried out 115In nuclear quadrupole resonance (NQR) measurements in CeCoIn 5 under pressure P. The obtained nuclear spin-lattice relaxation rate, 1 / T 1 , of 115In at ambient pressure varies in proportion to T 1 / 4 in the normal state, and T 3 below the superconducting transition temperature T C . The results show that the system locates just at the antiferromagnetic AF instability and the anisotropic superconductivity with line nodes appears. The value of 1 / T 1 is strongly suppressed with increasing P, indicating that P moves the system away from the AF instability. The Fermi-liquid behavior was observed at the high P region. The P dependence of 1 / T 1 in the superconducting state shows that the magnitude of the superconducting energy gap scales with its T C up to 3 GPa.
Journal Article•
TL;DR: The filled skutterudite compound Pr 0.87Fe4Sb12 was prepared in single-crystal form and characterized via x-ray-diffraction, neutron diffraction, specific-heat, electrical-resistivity, and magnetization measurements.
Abstract: The filled skutterudite compound Pr 0.87Fe4Sb12 was prepared in single-crystal form and characterized via x-ray-diffraction, neutron-diffraction, specific-heat, electrical-resistivity, and magnetization measurements. Long-range magnetic ordering occurs at Tc<4.1 K, with the bulk magnetization described by the critical exponentsb=0.57,g=0.884, andd=2.55. The magnetic structure consists of ordered moments on both Pr and Fe sites and may involve a ferrimagnetic arrangement. The electrical resistivity exhibits a very weak dependence on both applied magnetic field and pressure at most temperatures, but at low temperatures, its power-law temperature-dependence varies with magnetic field. Specific-heat measurements indicate an enhanced effective mass.
TL;DR: In this article, the temperature dependence of the lower critical field H C 1 (T ) was obtained from measurements of dc isothermal magnetization curves for a collection of PrOs4Sb12 single crystals.
Abstract: From measurements of dc isothermal magnetization curves for a collection of PrOs4Sb12 single crystals, we have obtained the temperature dependence of the lower critical field H C 1 ( T ) . At temperatures as low as 0.05 K, the value of H C 1 does not exceed 20 Oe. A comparison of the Meissner slope, d M / d H in the limit H → 0 , with ac-magnetic susceptibility for the same sample allowed us to investigate in detail the region where two distinct superconducting anomalies have been reported. d M / d H H → 0 is temperature independent only below about 1.5 K, i.e., well below T C 2 ≃ 1.75 K .