G. M. Schmiedeshoff

Occidental College, Los Angeles, California, United States

Are you G. M. Schmiedeshoff?

Claim your profile

Publications (71)101.5 Total impact

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We report on the development of a sensitive dilatometer based upon a AFM piezocantilever. This dilatometer has been tested at temperatures down to 25 mK and in magnetic fields up to 16 T. The layered heavy fermion superconductor $CeCoIn_5$ and its non-magnetic analog $LaRhIn_5$ have been measured to demonstrate its use in detecting phase transitions and quantum oscillations. In addition, using this dilatometer, a simultaneous multi-axis dilation measurement has been done. This compact dilatometer has many advantages such as its ability to measure very small samples with lengths at sub-mm levels, low temperature and field dependence, ability to rotate, and works well irrespective of being in a changing liquid or gas environment (i.e. within a flow cryostat or mixing chamber).
    09/2013;
  • [Show abstract] [Hide abstract]
    ABSTRACT: YbBiPt is a stoichiometric heavy fermion compound with an enormous Sommerfeld coefficient and a magnetic ground state that can be suppressed by fields of about 4 kOe. We will present and discuss recent thermodynamic and transport measurements, and the evidence for field induced quantum criticality in this material. Work at Ames Laboratory was supported by the Department of Energy, Basic Energy Sciences under Contract No. DE-AC02-07CH11358. The National High Magnetic Field Laboratory was supported by the US National Science Foundation, the State of Florida and the US Department of Energy. Work at Occidental College was supported by the National Science Foundation under DMR-1006118.
    03/2013;
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In this paper, we present the systematic measurements of the temperature and magnetic field dependences of the thermodynamic and transport properties of the Yb-based heavy fermion YbPtBi for temperatures down to 0.02 K with magnetic fields up to 140 kOe to address the possible existence of a field-tuned quantum critical point. Measurements of magnetic field and temperature dependent resistivity, specific heat, thermal expansion, Hall effect, and thermoelectric power indicate that the AFM order can be suppressed by applied magnetic field of $H_{c}$ $\sim$ 4 kOe. In the $H-T$ phase diagram of YbPtBi, three regimes of its low temperature states emerges: (I) AFM state, characterized by spin density wave (SDW) like feature, which can be suppressed to $T$ = 0 by the relatively small magnetic field of $H_{c}$ $\sim$ 4\,kOe, (II) field induced anomalous state in which the electrical resistivity follows $\Delta\rho(T) \propto T^{1.5}$ between $H_{c}$ and $\sim$ 8 kOe, and (III) Fermi liquid (FL) state in which $\Delta\rho(T) \propto T^{2}$ for $H \geq$ 8 kOe. Regions I and II are separated at $T$ = 0 by what appears to be a quantum critical point. Whereas region III appears to be a FL associated with the hybridized 4$f$ states of Yb, region II may be a manifestation of a spin liquid state.
    Physical review. B, Condensed matter 11/2012; 87(7). · 3.66 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: We report magnetotransport measurements made on the anisotropic magnetic superconductor ErNi2B2C. We observe a minimum in the magnetoresistance with fields along the a-axis, a behavior consistent with the high field quenching of magnetic scattering. When the field is applied along the c-axis the magnetoresistance is positive. The temperature of the antiferromagnetic phase transition is depressed by magnetic fields applied along the c-axis (as it is along the a-axis) and is suppressed near 17 T. A feature in the first derivative of the temperature dependent resistivity may be related to the weak ferromagnetic phase. We find the temperature at which this feature occurs to be independent of magnetic fields to 18 T.
    International Journal of Modern Physics B 01/2012; 16(20n22). · 0.46 Impact Factor
  • G. M. Schmiedeshoff, S. L. Bud'Ko, P. C. Canfield
    [Show abstract] [Hide abstract]
    ABSTRACT: YbAgGe is a stoichiometric heavy fermion antiferromagnet that exhibits field-induced quantum criticality. We present and discuss thermal expansion and magnetostriction measurements that reveal a new field-induced state. On the low-field side of this state we find evidence for a first-order phase transition and suggest that YbAgGe may be close to a quantum critical end point at 4.5 T. On the high-field side we find evidence for a second-order phase transition suppressed to a quantum critical point near 7.2 T. We will discuss these results in light of global phase diagrams proposed for Kondo lattice systems. Work at Occidental College was supported by the National Science Foundation under DMR-1006118. Work at Ames Laboratory was supported by the Department of Energy, Basic Energy Sciences under Contract No. DE-AC02-07CH11358.
    03/2011;
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Dilation and thermopower measurements on YbAgGe, a heavy-fermion antiferromagnet, clarify and refine the magnetic ?field-temperature (H-T) phase diagram and reveal a field-induced phase with T-linear resistivity. On the low-H side of this phase we find evidence for a first-order transition and suggest that YbAgGe at 4.5 T may be close to a quantum critical end point. On the high-H side our results are consistent with a second-order transition suppressed to a quantum critical point near 7.2 T. We discuss these results in light of global phase diagrams proposed for Kondo lattice systems.
    Physical review. B, Condensed matter 02/2011; · 3.66 Impact Factor
  • Source
    J-H Park, D Graf, T P Murphy, G M Schmiedeshoff, S W Tozer
    [Show abstract] [Hide abstract]
    ABSTRACT: Thermal expansion, or dilation, is closely related to the specific heat, and provides useful information regarding material properties. The accurate measurement of dilation in confined spaces coupled with other limiting experimental environments such as low temperatures and rapidly changing high magnetic fields requires a new sensitive millimeter size dilatometer that has little or no temperature and field dependence. We have designed an ultracompact dilatometer using an atomic force microscope piezoresistive cantilever as the sensing element and demonstrated its versatility by studying the charge density waves in alpha uranium to high magnetic fields (up to 31 T). The performance of this piezoresistive dilatometer was comparable to that of a titanium capacitive dilatometer.
    The Review of scientific instruments 11/2009; 80(11):116101. · 1.52 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: We have measured the molar volume of a nearly saturated He-He mixture, at temperatures below 100 mK and in magnetic fields to 16 T, by immersing capacitive dilatometers in the dilute phase of a top-loading dilution refrigerator. In zero magnetic field the coefficient of volume thermal expansion is negative and shows the linear temperature dependence expected of a Fermi liquid. Subject to experimental assumptions, we find the fractional increase in molar volume with magnetic field at 20 mK and 16 T to be about 0.01%.
    Philosophical Magazine A 08/2009; 89:2071-2078.
  • G.M. Schmiedeshoff, J.L. Smith
    [Show abstract] [Hide abstract]
    ABSTRACT: We have measured the electrical resistivity of a single crystal of UBe13 below 1 K and in high magnetic fields to 33 T. The resistivity exhibits the T 2 dependence characteristic of a Fermi liquid at low temperatures. The field dependence of the coefficient of the T 2 term in the resistivity suggests that the heavy fermion state is suppressed by high magnetic fields. We discuss these results in light of a proposed field-induced quantum critical point immersed in the novel superconducting state of this compound.
    Philosophical Magazine A 08/2009; 89(Nos. 22–24):1839-1843.
  • [Show abstract] [Hide abstract]
    ABSTRACT: We have measured the thermal expansion of the heavy fermion borocarbide YbNi2B2C from room temperature to about 0.5 K using a capacitive dilatometer. The thermal expansion is anisotropic, is consistent with a crystal-field splitting on the order of 120 K, and with intermediate-valence behavior at low temperatures. The effective Grüneisen parameter is temperature dependent and we estimate its value at T = 0 to be about -7, consistent with a moderately enhanced heavy fermion state.
    Journal of Physics Conference Series 03/2009; 150(4):042177.
  • [Show abstract] [Hide abstract]
    ABSTRACT: We present heat capacity and anisotropic thermal expansion data for Ba(Fe1-xCox)2As2. Evolution of structural/magnetic phase transition with Co-concentration is clearly detected by both measurements. Anisotropic pressure derivatives of the superconducting transition temperature are evaluated via the Ehrenfest relations and compared with directly measured hydrostatic dTc/dP.
    03/2009;
  • [Show abstract] [Hide abstract]
    ABSTRACT: YbAgGe is a stoichiometric heavy fermion compound that exhibits antiferromagnetic order and field induced quantum criticality. We will discuss this behavior, and present a unified phase diagram of this compound in the T-H plane, in light of our recent thermal expansion and magnetostriction measurements. We find a remarkable agreement between thermodynamic, transport and microscopic measurements on this model system. Work at Occidental College was supported by the National Science Foundation under DMR-0704406. Work at the Ames Laboratory was supported by the Department of Energy, Basic Energy Sciences under Contract No. DE-AC02-07CH11358.
    03/2009;
  • Source
    S. L. Bud’ko, N. Ni, S. Nandi, G. M. Schmiedeshoff, P. C. Canfield
    [Show abstract] [Hide abstract]
    ABSTRACT: Heat capacity and anisotropic thermal expansion were measured for Ba(Fe1−xCox)2As2 (x=0,0.038,0.074) single crystals. Thermal expansion is anisotropic and, in tetragonal phase, is significantly higher along the c axis. Previously reported phase transitions, including possibly split structural and magnetic for x=0.038, are clearly seen in both measurements. Uniaxial pressure derivatives of the superconducting transition temperature inferred from the Ehrenfest relation have opposite signs for in-plane and c-axis pressures for both Ba(Fe0.962Co0.038)2As2 and Ba(Fe0.926Co0.074)2As2, with the opposite sign of this anisotropy.
    Physical Review B 02/2009; 79(5). · 3.66 Impact Factor
  • Peter S. Riseborough, George M. Schmiedeshoff, James L. Smith
    [Show abstract] [Hide abstract]
    ABSTRACT: Heavy Fermion Superconductivity: A state of the art review of superconductivity in the Heavy Fermion metals is presented. Many important results are given. Theory and experiment are compared and critically discussed.
    04/2008: pages 1031-1154;
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Data on temperature-dependent, anisotropic thermal expansion in pure and doped RAgSb(2) (R = Y, Sm, La) single crystals are presented. Using the Ehrenfest relation and heat capacity measurements, uniaxial pressure derivatives for long range magnetic ordering and charge density wave transition temperatures are evaluated and compared with the results of the direct measurements under hydrostatic pressure. In-plane and c-axis pressure have opposite effects on the phase transitions in these materials, with in-plane effects being significantly weaker. Quantum oscillations in magnetostriction were observed for the three pure compounds, with the possible detection of new frequencies in SmAgSb(2) and LaAgSb(2). The uniaxial (along the c-axis) pressure derivatives of the dominant extreme orbits (β) were evaluated for YAgSb(2) and LaAgSb(2).
    Journal of Physics Condensed Matter 03/2008; 20(11):115210. · 2.22 Impact Factor
  • S. L. Bud'Ko, P. C. Canfield, G. M. Schmiedeshoff
    [Show abstract] [Hide abstract]
    ABSTRACT: In order to test whether the Ehrenfest relation is applicable to the spin glass ``transition,'' we report temperature-dependent heat capacity and thermal expansion measurements on an ``ideal'' spin glass material: single grain icosahedral Gd-Mg-Zn quasicrystal and its non-magnetic counterpart, Y-Mg-Zn. Spin-glass state related signatures are clearly seen in the Gd-Mg-Zn data sets. Directly measured pressure dependence of the freezing temperature in Gd-Mg-Zn is compared to its evaluation through the Ehrenfest relation.
    03/2008;
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We present thermal expansion and longitudinal magnetostriction data for cubic RAl3 (R = Tm, Yb, Lu) single crystals. The thermal expansion coefficient for YbAl3 is consistent with an intermediate valence of the Yb ion, whereas the data for TmAl3 show crystal electric field contributions and have strong magnetic field dependencies. de Haas-van Alphen-like oscillations were observed in the magnetostriction data of YbAl3 and LuAl3, several new extreme orbits were measured and their effective masses were estimated. Zero and 140 kOe specific heat data taken on both LuAl3 and TmAl3 for T < 200 K allow for the determination of a CEF splitting scheme for TmAl3.
    Journal of Physics Condensed Matter 10/2007; · 2.22 Impact Factor
  • Source
    S L Bud'ko, P C Canfield, E Morosan, R J Cava, G M Schmiedeshoff
    [Show abstract] [Hide abstract]
    ABSTRACT: We report measurements of thermal expansion on a number of polycrystalline Cu(x)TiSe(2) samples corresponding to the parts of x-T phase diagram with different ground states, as well as the pressure dependence of the superconducting transition temperature, T(c), for samples with three different values of Cu doping. Thermal expansion data suggest that the x-T phase diagram may be more complex than initially reported. T(c) data at elevated pressure can be scaled to the ambient pressure Cu(x)TiSe(2) phase diagram; however, significantly different scaling factors are needed to accommodate the literature data on the charge density wave transition suppression under pressure.
    Journal of Physics Condensed Matter 04/2007; 19(17):176230. · 2.22 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: We have measured the specific heat and thermal expansion of some polycrystalline BeCu alloys with an atomic concentration of Cu up to 3%. We will present and discuss our measurements in the context of a Gruneisen analysis.
    03/2007;
  • [Show abstract] [Hide abstract]
    ABSTRACT: Using a capacitive dilatometer designed to operate on the rotating stage of a top loading dilution refrigerator probe, we measured the magnetorestriction ( L(H)-L(0))/L(0), of the Heavy Fermion Superconductor CeCoIn5, along all three crystallographic direction, and with the magnetic field applied parallel both to the superconducting ab-planes and to the c-axis. When B||ab, the c-axis magnetorestriction features, besides a sharp jump at the upper critical field, a continuous, second-order like, transition at a lower field, which is consistent with previous observations from specific heat measurements. Our results are consistent with a field induced modulation of the superconducting order parameter (FFLO state), rather than with a field induced magnetic ordering.
    03/2007;

Publication Stats

264 Citations
101.50 Total Impact Points

Institutions

  • 1993–2012
    • Occidental College
      • Department of Physics
      Los Angeles, California, United States
  • 2007–2009
    • Florida State University
      • Department of Physics
      Tallahassee, FL, United States
  • 2008
    • San Diego State University
      • Department of Physics
      San Diego, California, United States
  • 2007–2008
    • Iowa State University
      • Department of Physics and Astronomy
      Ames, IA, United States
  • 1996–1997
    • National High Magnetic Field Laboratory
      Tallahassee, Florida, United States
    • University of California, Riverside
      • Department of Physics and Astronomy
      Riverside, California, United States
  • 1988–1992
    • Bowdoin College
      Brunswick, Maine, United States
  • 1987
    • Massachusetts Institute of Technology
      Cambridge, Massachusetts, United States