Ferromagnetic Quantum Critical Endpoint in UCoAl

Aoki, Dai; Combier, Tristan; Taufour, Valentin; Matsuda, Tatsuma D.; Knebel, G.; Kotegawa, Hisashi; Flouquet, J.

doi:10.1143/jpsj.80.094711

Cited by 99 publications

(127 citation statements)

References 61 publications

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“…Similar experimental studies have revealed other wing-structure phase diagrams in UGe 2 [8,30,31] (also shown in Fig. 6 for comparison), Sr 3 Ru 2 O 7 [37], ZrZn 2 [9], UCoAl [35,36,40]. The behavior near the tricritical point could not be studied in Sr 3 Ru 2 O 7 and UCoAl because those compounds are already in the paramagnetic regime at ambient pressure.…”

Section: Quantum Wingsupporting

confidence: 61%

“…Besides UGe 2 and LaCrGe 3 , two ferromagnetic states have also been reported in ZrZn 2 [34]. In UCoAl, the anomaly corresponding to the field induced transition to the FM state shows two peaks in the ac susceptibility [35] and two kinks forming a plateau in electrical resistivity [36]. Two peaks in the ac susceptibility have also been reported in the metamagnetic transition of Sr 3 Ru 2 O 7 [37].…”

Section: Quantum Wingmentioning

confidence: 89%

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Ferromagnetic quantum criticality: New aspects from the phase diagram of LaCrGe3

Taufour

Kaluarachchi

Bud’ko

et al. 2018

Physica B: Condensed Matter

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Recent theoretical and experimental studies have shown that ferromagnetic quantum criticality is always avoided in clean systems. Two possibilities have been identified. In the first scenario, the ferromagnetic transition becomes of the first order at a tricritical point before being suppressed. A wing structure phase diagram is observed indicating the possibility of a new type of quantum critical point under magnetic field. In a second scenario, a transition to a modulated magnetic phase occurs. Our recent studies on the compound LaCrGe 3 illustrate a third scenario where not only a new magnetic phase occurs, but also a change of order of the transition at a tricritical point leading to a wing-structure phase diagram. Careful experimental study of the phase diagram near the tricritical point also illustrates new rules near this type of point.

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Section: Quantum Wingsupporting

confidence: 61%

Section: Quantum Wingmentioning

confidence: 89%

Ferromagnetic quantum criticality: New aspects from the phase diagram of LaCrGe3

Taufour

Kaluarachchi

Bud’ko

et al. 2018

Physica B: Condensed Matter

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“…7 is in excellent agreement with previous transport measurements. 10 Magnetization measurements 9 led to lower pressure dependence of B m , as mentioned above. This discrepancy probably comes from pressure inhomogeneities or differences in the crystal quality.…”

Section: Hall Effect Under High Pressurementioning

confidence: 69%

“…The metamagnetic transition at B m is of first order, attested by a hysteresis between increasing and decreasing field magnetization curves. 8,10 The hysteresis reduces and the metamagnetic transition gradually broadens as temperature increases, until it ends at T 0 = 12 K, marking the first-order critical end point (CEP). For T > T 0 a pseudo-metamagnetic transition fades out into a broad crossover region.…”

Section: Methodsmentioning

confidence: 99%

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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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Heavy fermions in a high magnetic field

Aoki

Knafo

Sheikin

2013

Comptes Rendus. Physique

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We give an overview on experimental studies performed in the last 25 years on heavy-fermion systems in high magnetic field. The properties of field-induced magnetic transitions in heavy-fermion materials close to a quantum antiferromagnetic-to-paramagnetic instability are presented. Effects of a high magnetic field to the Fermi surface, in particular the splitting of spin-up and spin-down bands, are also considered. Finally, we review on recent advances on the study of non-centrosymmetric compounds and ferromagnetic superconductors in a high magnetic field.To cite this article: D. Aoki, W. Knafo, and I. Sheikin, C. R. Physique XX (2012). RésuméFermions lourds en champ magnétique intense. Cette revue donne un aperçu desétudes expérimentales faites depuis 25 ans sur les systèmesà fermions lourds en champ magnétique intense. Les propriétés des transitions de phase magnétiques de composés proches d'une instabilité antiferromagnétique sont présentées. Les effets d'un champ magnétique intense sur la surface de Fermi, en particulier la séparation des bandes de spin "up" et "down", sont aussi considérées. Finalement, nous faisons le point sur les avancées récentes dans l'étude en champ magnétique intense de composés non-centrosymmétriques et de supraconducteurs ferromagnétiques.

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Ferromagnetic Quantum Critical Endpoint in UCoAl

Cited by 99 publications

References 61 publications

Ferromagnetic quantum criticality: New aspects from the phase diagram of LaCrGe3

Ferromagnetic quantum criticality: New aspects from the phase diagram of LaCrGe3

Ferromagnetic Quantum Criticality Studied by Hall Effect Measurements in UCoAl

Heavy fermions in a high magnetic field

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