Entropy Constraints in the Ground State Formation of Magnetically Frustrated Systems

Sereni, J. G.

doi:10.1007/s10909-017-1828-5

Cited by 8 publications

(10 citation statements)

References 39 publications

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“…The strong increase of the density of magnetic excitations is reflected in power law dependencies of the specific heat: C m (T )/T ∝ 1/T Q , with exponents ranging between 1 < Q ≤ 2 that clearly exceed the C m /T | T →0 values of usual nonfermi-liquids (NFL) [3] that increase as a −ln(T /T 0 ) with decreasing temperature. These compounds can be called very-heavy fermions (VHF) because their C m /T | T →0 range between ≈ 5 and ≈ 12 J/molK 2 [4].…”

Section: Introductionmentioning

confidence: 99%

Physical properties of the magnetically frustrated very-heavy-fermion compound YbCu4Ni

Sereni

Čurlík

Giovannini³

et al. 2018

Phys. Rev. B

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The physical properties of the very heavy fermion YbCu4Ni were characterized through structural, magnetic, thermal and transport studies along nearly four decades of temperature ranging between 50 milikelvin and 300 K. At high temperature, the crystal electric field levels splitting was determined with ∆1(Γ6) = 85 K and ∆2(Γ8) ≈ 200 K, the latter being a quartet in this cubic symmetry. An effective magnetic moment µ ef f ≈ 3µB is evaluated for the Γ7 ground state, while at high temperature the value for a Yb 3+ ion is observed. At low temperature this compounds shows the typical behavior of a magnetically frustrated system undergoing a change of regime at a characteristic temperature T * ≈ 200 mK into a sort of Fermi-liquid type 'plateau'of the specific heat: Cm/T |T →0 = const. The change in the temperature dependence of the specific heat coincides with a maximum and a discontinuity in respective inductive and dissipative components of the ac-susceptibility. More details from the nature of this ground state are revealed by the specific heat behavior under applied magnetic field.

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Section: Introductionmentioning

confidence: 99%

Physical properties of the magnetically frustrated very-heavy-fermion compound YbCu4Ni

Sereni

Čurlík

Giovannini³

et al. 2018

Phys. Rev. B

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“…1a belong to groups (II) and (III) respectively and better apply for CTD requirements because of their moderate slope allows a more convenient heat absorption more homogeneously distributed in temperature. Within group (II) one can mention YbCu 4 Ni [8] which represents the family of compounds showing a C m /T | T →0 ≈ 7.5±0.5 J/mol K 2 'plateau' followed by a common power law above a change of regime at T = T * [11]. The compounds included in group (III) are characterized by showing NFL behavior, like (Yb,Sc)Co 2 Zn 20 [7] and CeNi 9−x T x (where T = Co [14] with x = 0.1, and T = Cu with x = 0.4 [15] respectively).…”

Section: Analysis Of Thermomagnetic Propertiesmentioning

confidence: 99%

“…Among them are the recently synthesized Yb-intermetallic compounds [5][6][7][8][9][10], some of which have been tested as proper candidates for the proposed improvements because of their very large C m /T | T →0 values. These compounds were labeled as very HF (VHF) [11] because they largely exceed the values of classical HF [12]. According to their physical behavior within the mK range three well defined types of C m (T )/T behaviors were recognized [13]: (I) the actual VHF with C m /T | T →0 > 10 J/molK 2 , (II) those showing a constant C m /T | T →0 'plateau' around 7 J/molK 2 below a characteristic temperature T * and (III) those belonging to the non-Fermi-liquid (NFL) family [12] because of their C m (T )/T ∝ − ln(T /T 0 ) dependence.…”

Section: Introductionmentioning

confidence: 99%

Thermomagnetic properties of very heavy fermions suitable for adiabatic demagnetisation refrigeration at low temperature

Sereni

2020

Philosophical Magazine

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With the aim of improving the performance of classical paramagnetic salts for adiabatic refrigeration processes at the sub-Kelvin range, relevant thermodynamic parameters of some new Ybbased intermetallic compounds are analyzed and compared. Two alternative potential applications are recognized, like those requiring fixed temperature reference points to be reached applying low intensity magnetic fields and those requiring controlled thermal drift for temperature dependent studies. Different thermomagnetic entropy S(T, B) trajectories were identified depending on respective specific heat behaviors at very low temperature. To gain insight into the criteria to be used for a proper choice of suitable materials in respective applications, some simple relationships are proposed to facilitate a comparative description of their magnetocaloric behavior, including the referent Cerium-Magnesium-Nitride (CMN) salt in these comparisons.

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“…This is due to the fact that no order parameter, able to reduce the GS degeneracy, can develop. Since entropy accumulation cannot exceed the available degrees of freedom provided by the doublet GS, the system is forced into an alternative minimum of the free en-ergy [20]. Since this transition occurs in a continuous way, no discontinuity (or jump) is observed in C m (T )/T , whilst such a discontinuity is observed in ∂C m /∂T , i.e.…”

Section: A Entropy Trajectory and Magnetic Frustrationmentioning

confidence: 99%

Physical properties of CeIrSi with trillium-lattice frustrated magnetism

et al. 2019

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Magnetic (χ), transport (ρ) and heat capacity (Cm) properties of CeIrSi are investigated to elucidate the effect of geometric frustration in this compound with trillium type structure because, notwithstanding its robust effective moment, µ eff ≈ 2.46µB, this Ce-lattice compound does not undergo a magnetic transition. In spite of that it shows broad Cm(T )/T and χ(T ) maxima centered at Tmax ≈ 1.5 K, while a ρ ∝ T 2 thermal dependence, characteristic of electronic spin coherent fluctuations, is observed below T coh ≈ 2.5 K. Magnetic field does not affect significantly the position of the mentioned maxima up to ≈ 1 T, though χ(T ) shows an incipient structure that completely vanishes at µ0H ≈ 1 T. Concerning the ρ ∝ T 2 dependence, it is practically not affected by magnetic field up to µ0H = 9 T, with the residual resistivity ρ0(H) slightly decreasing and T coh (H) increasing. These results are compared with the physical properties observed in other frustrated intermetallic compounds.

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Entropy Constraints in the Ground State Formation of Magnetically Frustrated Systems

Cited by 8 publications

References 39 publications

Physical properties of the magnetically frustrated very-heavy-fermion compound YbCu4Ni

Physical properties of the magnetically frustrated very-heavy-fermion compound YbCu4Ni

Thermomagnetic properties of very heavy fermions suitable for adiabatic demagnetisation refrigeration at low temperature

Physical properties of CeIrSi with trillium-lattice frustrated magnetism

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