Thermoelectric power investigations of YbAgGe across the quantum critical point

Abstract

The magnetic field and temperature dependences of the thermoelectric power (TEP) of the antiferromagnetically ordered heavy fermion compound YbAgGe are measured across the field-induced quantum critical point. These TEP measurements reproduce the earlier H-T phase diagram and identify an additional domelike phase between ∼45and ∼70 kOe. On the low-field side of this region, H>Hc∼45 kOe, the sign of the TEP changes from negative to positive; on the high-field side of this region, H≈70 kOe, a nonFermi-liquid state is evidenced as the logarithmic temperature dependence of S(T)/T, in agreement with previous specific heat results C(T)/T∝−log(T). For higher fields, H>70 kOe, the observed large value of α, S(T)=αT, is indicative of the heavy fermion state and shows a correlation with C(T)/T. Keywords Physics and Astronomy Disciplines Condensed Matter Physics CommentsThis article is from Physical Review B 82 (2010) The magnetic field and temperature dependences of the thermoelectric power ͑TEP͒ of the antiferromagnetically ordered heavy fermion compound YbAgGe are measured across the field-induced quantum critical point. These TEP measurements reproduce the earlier H-T phase diagram and identify an additional domelike phase between ϳ45 and ϳ70 kOe. On the low-field side of this region, H Ͼ H c ϳ 45 kOe, the sign of the TEP changes from negative to positive; on the high-field side of this region, H Ϸ 70 kOe, a non-Fermi-liquid state is evidenced as the logarithmic temperature dependence of S͑T͒ / T, in agreement with previous specific heat results C͑T͒ / T ϰ −log͑T͒. For higher fields, H Ͼ 70 kOe, the observed large value of ␣, S͑T͒ = ␣T, is indicative of the heavy fermion state and shows a correlation with C͑T͒ / T.

Quantum Bicriticality in the Heavy-Fermion Metamagnet YbAgGe

“…[14]. The regions a to d are interpreted as symmetry-broken phases because their boundaries have been located by anomalies in thermodynamics and transport [14,15,17], although some of them are only weak. The antiferromagnetic ordering wave vectors of the a, b, and c phases were identified by neutron scattering [16,18,19], whereas the order parameter of the d phase remains elusive.…”

Ubiquity of amplitude-modulated magnetic ordering in the H−T phase diagram of the frustrated non-Fermi-liquid YbAgGe

“…Thus the anisotropy is essentially the same as in the TmAgGe [14] member of the RAgGe family as well as the isostructural TbPtIn [14]. Low-temperature thermodynamic and transport results [1][2][3][4][5]14,17,18] distinguish YbAgGe from other RAgGe compounds with well localised R moments. The electronic specific-heat coefficient γ ranges from 0.15 to 1 J/molK 2 and the entropy release is only ∼5% of Rln2 at 1 K [1,3,14].…”

“…Several topical themes of modern solid-state researchfrustrated magnetism, non-Fermi-liquid behavior, and fieldinduced quantum criticality-converge in YbAgGe, a system that has been in the focus of experimental studies for more than a decade [1][2][3][4][5][6][7][8][9][10][11][12].…”

“…The complex H-T phase diagram of YbAgGe [Fig. 1(a)], constructed from detailed bulk measurements [1][2][3][4][5]14,17,18], contains up to six different phases labeled by the letters a to f [5]. Earlier magnetic neutron elastic-scattering studies were able to identify the ordering wave vectors of the first two of these phases.…”

Magnetic structure and crystalline electric field effects in the triangular antiferromagnet CePtAl4Ge2

“…Experimentally, frustrated magnetic structures have been reported in a breadth of f -electron compounds including CePdAl [7,11], UNi 4 B [12], YbPtIn [13], and YbAgGe [13,14]. Magnetic frustration also gives rise to a skyrmion lattice in Gd 2 PdSi 3 [15], an electronic nematic state in CeRhIn 5 [16][17][18], and field-/pressure-induced quantum criticality in CePdAl [19][20][21][22], CeAgGe [23][24][25], and CeRhSn [26][27][28]. Several theoretical works proposed that these electronic states in f -electron metallic systems could be ascribed to the interplay between the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction, the Kondo effect, and the strength of the magnetic frustration [29][30][31].…”