Scaling of the magnetic entropy and magnetization in

Gegenwart, P.; Tokiwa, Y.; Neumaier, K.; Geibel, C.; Steglich, F.

doi:10.1016/j.physb.2004.12.044

Cited by 7 publications

(12 citation statements)

References 6 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Similar exponents for Γ mag and −dM/dT were found in β-YbAlB 4 [8] and Au 51 Al 34 Yb 15 [10]. For YbRh 2 (Si 0.95 Ge 0.05 ) 2 a slightly different behavior, −dM/dT ∼ B −4/3 , has been observed [23].…”

supporting

confidence: 73%

T/Bscaling without quasiparticle mass divergence:YbCo2Ge4

et al. 2016

View full text Add to dashboard Cite

YbCo2Ge4 is a clean paramagnetic Kondo lattice which displays non-Fermi liquid behavior. We report a detailed investigation of the specific heat, magnetic Grüneisen parameter (Γmag) and temperature derivative of the magnetization (M ) on a high-quality single crystal at temperatures down to 0.1 K and magnetic fields up to 7 T. Γmag and dM/dT display a divergence upon cooling and obey T /B scaling. Similar behavior has previously been found in several other Yb-based Kondo lattices and related to a zero-field quantum critical point without fine tuning of pressure or composition. However, in the approach of B → 0 the electronic heat capacity coefficient of YbCo2Ge4 saturates at low T , excluding ferromagnetic quantum criticality. This indicates that T /B scaling is insufficient to prove a zero-field quantum critical point. It is very unlikely, that a compound is accidentally located at such a special point in multidimensional phase space. Chemical substitution studies on CeNi 2 Ge 2 indeed suggest that this compound is actually located slightly beyond the QCP on the paramagnetic side [11], though the crossover between quantum critical and Fermi liquid behavior in the undoped material is too low in T to be detectable. Relatedly, for CeCoIn 5 the QCP is masked by superconductivity and the conclusion of zerofield quantum criticality relies on extrapolation [5]. On the other hand, for CeRhSn [4] and Pr 2 Ir 2 O 7 [6] zerofield quantum criticality originates from strong geometrical frustration which effectively suppresses long-range order. An even more exotic scenario would be the existence of an extended quantum critical regime. Such a quantum critical phase may be sensitive to the application of magnetic fields but stable over a substantial range of applied pressure. Evidence for pressure insensitivity of NFL behavior has been reported for β-YbAlB 4 [9] and Au 51 Al 34 Yb 15 [10]. However, the nature of a quantum critical phase, instead of singlar QCP, remains unclear. ZeroIn this paper, we discuss a new Yb-based Kondo lattice, YbCo 2 Ge 4 [12], which displays similar temperature over magnetic field, T /B scaling behavior as found previously for β-YbAlB 4 [7,8] and the quasicrystal Au 51 Al 34 Yb 15 . Note, that in contrast to the case of fieldinduced QCPs [13,14], it involves the applied field B and not a tuning parameter r = (B − B c )/B c , because the critical field B c = 0. We observe a divergence of the magnetic Grüneisen parameter and the temperature derivative of the magnetization dM/dT upon cooling in the limit of zero field similar as in the above mentioned examples. However, the heat capacity coefficient is almost constant in the respective T -B range, excluding quantum criticality as origin of T /B scaling.

show abstract

supporting

confidence: 73%

T/Bscaling without quasiparticle mass divergence:YbCo2Ge4

et al. 2016

View full text Add to dashboard Cite

show abstract

“…In addition, the temperature-field scaling observed in YbRh 2 (Si 1−x Ge x ) 2 with x = 5% (Ref. 36) is in accord with ferromagnetic criticality, provided that one interprets (B − B c ) (where B c = 0.027 T is tiny) as the field conjugate to the order parameter. However, other observations in YbRh 2 Si 2 appear inconsistent with this idea of 2d FM criticality: 37 for example, the fractional exponent observed in the T dependence of the uniform susceptibility χ u (T ) cannot be easily explained with this scenario.…”

Section: B Ybrh2si2mentioning

confidence: 89%

“…( 38), the classical dimensional crossover from 2d to 3d is perturbative as it is located outside the classical Ginzburg region. Here, we can use expression (36) for the correlation length to obtain…”

Section: Phase Boundarymentioning

confidence: 99%

See 1 more Smart Citation

Dimensional crossover in quantum critical metallic magnets

et al. 2008

View full text Add to dashboard Cite

Nearly magnetic metals often have layered lattice structures, consisting of coupled planes. In such a situation, physical properties will display, upon decreasing temperature or energy, a dimensional crossover from two-dimensional (2d) to three-dimensional (3d) behavior, which is particularly interesting near quantum criticality. Here we study this crossover in thermodynamics using a suitably generalized Landau-Ginzburg-Wilson approach to the critical behavior, combined with renormalization group techniques. We focus on two experimentally relevant cases: the crossover from a 2d to a 3d antiferromagnet, and the crossover from a 2d ferromagnet to a 3d antiferromagnet. We discuss the location of phase boundary and crossover lines and determine the crossover functions for important thermodynamic quantities. As naive scaling does not apply at and above the upper critical dimension, two crossover scales arise which can be associated with separate dimensional crossovers of classical and quantum fluctuations, respectively. In particular, we find an intermediate regime with novel power laws where the quantum fluctuations still have a 2d and the classical fluctuations already have a 3d character. For the ferromagnet-to-antiferromagnet crossover, the mismatch of the dynamical exponents between the 2d and 3d regimes leads to an even richer crossover structure, with an interesting 2d non-critical regime sandwiched between two critical regimes. For all cases, we find that thermal expansion and compressibility are particularly sensitive probes of the dimensional crossover. Finally, we relate our results to experiments on the quantum critical heavy-fermion metals CeCu(6-x)Au(x), YbRh(2)Si(2) and CeCoIn(5).Comment: 18 pages, 8 figures, published versio

show abstract

“…However, in the regime close to the QCP typically only a very small amount of the entropy is involved in these materials due to the onset of Kondo screening as the temperature is lowered below T K . For Ge-doped YbRh 2 Si 2 with T K ≈ 20 K, for example, only about 10% (2%) of R ln 2 is available below 1 K (0.1 K) [91], which is too small for practical applications. Ideal for involving a significant amount of entropy in the cooling process would be a HF metal with small T K , being located close to a QCP at very low magnetic fields.…”

Section: Cooling Through Quantum Criticalitymentioning

confidence: 99%

Grüneisen parameter studies on heavy fermion quantum criticality

Gegenwart

2016

Rep. Prog. Phys.

View full text Add to dashboard Cite

The Grüneisen parameter, experimentally determined from the ratio of thermal expansion to specific heat, quantifies the pressure dependence of characteristic energy scales of matter. It is highly enhanced for Kondo lattice systems, whose properties are strongly dependent on the pressure sensitive antiferromagnetic exchange interaction between f- and conduction electrons. In this review, we focus on the divergence of the Grüneisen parameter and its magnetic analogue, the adiabatic magnetocaloric effect, for heavy-fermion metals near quantum critical points. We compare experimental results with current theoretical models, including the effect of strong geometrical frustration. We also discuss the possibility of using materials with the divergent magnetic Grüneisen parameter for adiabatic demagnetization cooling to very low temperatures.

show abstract

Scaling of the magnetic entropy and magnetization in

Cited by 7 publications

References 6 publications

T/Bscaling without quasiparticle mass divergence:YbCo2Ge4

T/Bscaling without quasiparticle mass divergence:YbCo2Ge4

Dimensional crossover in quantum critical metallic magnets

Grüneisen parameter studies on heavy fermion quantum criticality

Contact Info

Product

Resources

About