Quantum criticality in itinerant metamagnets

Zacharias, Mario; Garst, Markus

doi:10.1103/physrevb.87.075119

Cited by 11 publications

(26 citation statements)

References 39 publications

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“…This applies, for example, to the Kondo volume collapse transition at zero temperature, where the asymptotic critical behavior will be governed by a solid-solid QCEP [38,39]. It is also the case for the metamagnetic QCEP [40,41], where F corresponds to a magnetic field, which will be discussed in some detail in the next chapter. Similar reasoning applies to a metaelectric QCEP, where the Ising order parameter is identified with the variation in the longitudinal electric polarization, φ = P − P cr , which increases in a critical manner at some finite electric field.…”

Section: Isostructural Elastic Transitionsmentioning

confidence: 99%

“…[48] however without considering the feedback of the lattice to the critical behavior. Moreover, Zacharias and Garst [41] analyzed in detail the critical thermodynamics close to such a QCEP within the spin-fluctuations theory as proposed in Ref. [40].…”

Section: Metamagnetic Quantum Critical End Pointmentioning

confidence: 99%

“…The resulting thermodynamics was discussed in detail in Refs. [41,49]. A linear coupling γ 1 of the order parameter to the strain field, see Eq.…”

Section: Solid-solid Quantum Critical End Point Induced By Metamagnetmentioning

confidence: 99%

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Critical elasticity at zero and finite temperature

Zacharias

Rosch

Garst

2015

Eur. Phys. J. Spec. Top.

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Abstract. Elastic phase transitions of crystals and phase transitions whose order parameter couples linearly to elastic degrees of freedom are reviewed with particular focus on instabilities at zero temperature. A characteristic feature of these transitions is the suppression of critical fluctuations by long-range shear forces. As a consequence, at an elastic crystal symmetry-breaking quantum phase transition the phonon velocity vanishes only along certain crystallographic directions giving rise to critical phonon thermodynamics described by a stable Gaussian fixed point. At an isostructural solid-solid quantum critical end point, on the other hand, the complete suppression of critical fluctuations results in true mean-field critical behavior without a diverging correlation length. Whenever an order parameter couples bilinearly to the strain tensor, the critical properties are eventually governed by critical crystal elasticity. This is, for example, the case for quantum critical metamagnetism but also for the classical critical Mott end point at finite T . We discuss and compare the solid-solid end points expected close to the Mott transition in V2O3 and κ-(BEDT-TTF)2X.

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Section: Isostructural Elastic Transitionsmentioning

confidence: 99%

Section: Metamagnetic Quantum Critical End Pointmentioning

confidence: 99%

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Critical elasticity at zero and finite temperature

Zacharias

Rosch

Garst

2015

Eur. Phys. J. Spec. Top.

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“…Ref. 6,7). The main debate is whether a Lifshitz-like transition is associated with the occurence of metamagnetism.…”

Section: Introductionmentioning

confidence: 99%

“…9 It is worthwhile to remark that just above P QCEP in the paramagnetic ground state in high magnetic field, sharp pseudometamagnetism at B m will replace the sharp first order metamagnetism below P QCEP . 6 Further increasing pressure must lead to a broadening of the pseudometamagnetic transition.…”

Section: Introductionmentioning

confidence: 99%

Ferromagnetic Quantum Criticality Studied by Hall Effect Measurements in UCoAl

et al. 2013

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Hall effect measurements were performed under pressure and magnetic field up to 2.2 GPa and 16 T on a single crystal of UCoAl. At ambient pressure, the system undergoes a first order metamagnetic transition at the critical field Bm = 0.7 T from a paramagnetic ground state to a field-induced ferromagnetic state. The Hall signal is linear at low field and shows a step-like anomaly at the transition, with only little change of the Hall coefficient. The anomaly is sharpest at the temperature of the critical end point T0 = 12 K above which the first order metamagnetic transition becomes a crossover. Under pressure Bm increases and T0 decreases. The step-like anomaly in the Hall effect disappears at PM ≈ 1.3 GPa and the metamagnetic transition is not detected above the quantum critical end point (QCEP) at P∆ ≈ 1.7 GPa, Bm ≈ 7 T. Using magnetization data, we analyse our Hall resistivity data at ambient pressure in order to quantitatively account for both ordinary and anomalous contributions to the Hall effect. Under pressure, a drastic change in the field dependence of the Hall coefficient is found on crossing the QCEP. A possible Fermi surface change at Bm remains an open question.KEYWORDS: quantum critical end point, anomalous Hall effect, metamagnetism, ferromagnetism, UCoAl IntroductionThe metamagnetism in strongly correlated electron systems with Ising-type ferromagnetic (FM) behaviour is intensively studied because it produces a variety of unconventional effects. In some itinerant ferromagnets, such as UGe 2 1, 2 or ZrZn 2 , 3 one can drive the Curie temperature T C to 0 K by tuning an external control parameter like pressure, and the ground state is found to be paramagnetic (PM) above the quantum critical point (QCP). In theory, it has been suggested -and in some cases experimentally shown -that the second order ferromagnetic transition changes to first order at a tricritical point. 4 By applying a magnetic field above the critical point in the paramagnetic phase, such systems eventually recover their ferromagnetic state by undergoing a first-order metamagnetic transition at B m , drawing a wing-shape first order transition plane in the temperature (T ) -pressure (P ) -field (B) phase diagram. The first order transition terminates at high pressure and high field at T = 0 at the so-called quantum critical end point (QCEP). In this critical region, only few experiments were carried out because of the severe experimental conditions of low temperature, high pressure, and high field. [1][2][3]5 Due to the recent focus on quantum criticality, the metamagnetism in itinerant ferromagnets has been recently revisited theoretically (see e.g. Ref. 6,7). The main debate is whether a Lifshitz-like transition is associated with the occurence of metamagnetism.A good candidate to investigate itinerant metamagnetism is the heavy fermion compound UCoAl, with ZrNiAl-type hexagonal structure, space group P62m. At ambient pressure, its ground state is paramagnetic, with strong uniaxial magnetic anisotropy. By applying mag-

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Collapse of the magnetic moment under pressure of AFe2 (A=Y, Zr, Lu and Hf) in the cubic Laves phase

Zhang

2016

Journal of Magnetism and Magnetic Materials

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The electronic structures of four Laves phase iron compounds (e.g. YFe 2 , ZrFe 2 , LuFe 2 and HfFe 2 ) have been calculated by the state-of-the-art full potential electronic structure code. The magnetic moments collapse under hydrostatic pressure. This feature is found to be universal in these materials. Its electronic origin is provided by the sharp peaks in the density of states near the Fermi level. It is shown that a first order quantum phase transition can be expected under pressure in Y(Zr, or Lu)Fe 2 , while a second order one in HfFe 2 . The bonding characteristics are discussed to elucidate the equilibrium lattice constant variation. The large spontaneous volume magnetostriction gives one of the most important character of these compounds. Invar anomalies in these compounds can be partly explained by the current work when the fast continuous magnetic moment decrease at the decrease of the lattice constant was properly considered. This work may remind the experimentalists of these "old" compounds and exploration of the quantum properties under high pressures are greatly encouraged.

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Quantum criticality in itinerant metamagnets

Cited by 11 publications

References 39 publications

Critical elasticity at zero and finite temperature

Critical elasticity at zero and finite temperature

Ferromagnetic Quantum Criticality Studied by Hall Effect Measurements in UCoAl

Collapse of the magnetic moment under pressure of AFe2 (A=Y, Zr, Lu and Hf) in the cubic Laves phase

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