Tricritical Point and Wing Structure in the Itinerant Ferromagnet<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi>UGe</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:math>

Taufour, Valentin; Aoki, Dai; Knebel, G.; Flouquet, J.

doi:10.1103/physrevlett.105.217201

Cited by 157 publications

(190 citation statements)

References 34 publications

(70 reference statements)

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“…6. 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].…”

Section: Quantum Wingmentioning

confidence: 52%

“…In the same way as pressure can initially decrease the freezing point of water, physicist have been able to use pressure to decrease the Curie temperature to absolute zero temperature, leading to a quantum phase transition. Surprisingly, a variety of unconventional properties have been unveiled near the ferromagnetic quantum phase transition [1], including superconductivity [2][3][4][5], non-Fermi liquid behavior [6], tri-criticality [5,[7][8][9][10], and complex magnetic structures [11][12][13][14][15][16].…”

mentioning

confidence: 99%

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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 Wingmentioning

confidence: 52%

mentioning

confidence: 99%

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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“…It was suggested that UCoAl at ambient pressure is a similar state as UGe 2 at P ∼ 2 GPa, since the presence of the similar CEP was reported on UGe 2 in the pressure region of 1.5 < P < 3 GPa. 10 Above the CEP, the borderline of the first-order transition becomes bleared and the PM state continuously connects to the FM state as crossover. This CEP reminds us of a gas-liquid transition (see in Fig.…”

Section: Introductionmentioning

confidence: 99%

Universality and critical behavior at the critical endpoint in the itinerant-electron metamagnet UCoAl

et al. 2012

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We performed nuclear-magnetic-resonance (NMR) measurements on itinerant-electron metamagnet UCoAl in order to investigate the critical behavior of the magnetism near a metamagnetic (MM) critical endpoint (CEP). We derived c-axis magnetization Mc and its fluctuation Sc from the measurements of Knight shift and nuclear spin-lattice relaxation rate 1/T1 as a function of the c-axis external field (Hc) and temperature (T ). We developed contour plots of Mc and Sc on the Hc -T phase diagram, and observed the strong divergence of Sc at the CEP. The critical exponents of Mc and Sc near the CEP are estimated, and found to be close to the universal properties of a threedimensional (3-D) Ising model. We indicate that the critical phenomena at the itinerant-electron MM CEP in UCoAl have a common feature as a gas-liquid transition.

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“…Kb, 75.50.Cc, 75.30.Gw, 75.70.Tj Fluctuations near to quantum critical points in itinerant ferromagnets (FMs) can have drastic and often surprising effects. They generically render a priori continuous phase transitions first order at low temperatures [1][2][3][4][5]. In many systems, quantum phase transitions are preempted by the formation of superconducting [5][6][7], modulated magnetic [8], or unusual spin-glass phases [9,10].…”

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confidence: 99%

Fluctuation-Driven Magnetic Hard-Axis Ordering in Metallic Ferromagnets

2014

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We investigate the interplay of quantum fluctuations and magnetic anisotropies in metallic ferromagnets. Our central result is that fluctuations close to a quantum critical point can drive the moments to point along a magnetic hard axis. As a proof of concept, we show this behavior explicitly for a generic two-band model with local Coulomb and Hund's interactions, and a spin-orbit-induced easy plane anisotropy. The phase diagram is calculated within the fermionic quantum order-bydisorder approach, which is based on a self-consistent free energy expansion around a magnetically ordered state with unspecified orientation. Quantum fluctuations render the transition of the easyplane ferromagnet first-order below a tricritical point. At even lower temperatures, directionally dependent transverse fluctuations dominate the magnetic anisotropy and the moments flip to lie along the magnetic hard axis. We discuss our findings in the context of recent experiments that show this unusual ordering along the magnetic hard direction.PACS numbers: 74.40. Kb, 75.50.Cc, 75.30.Gw, 75.70.Tj Fluctuations near to quantum critical points in itinerant ferromagnets (FMs) can have drastic and often surprising effects. They generically render a priori continuous phase transitions first order at low temperatures [1][2][3][4][5]. In many systems, quantum phase transitions are preempted by the formation of superconducting [5][6][7], modulated magnetic [8], or unusual spin-glass phases [9,10]. Other metallic FMs show an unexpected ordering along the magnetic hard axis [11,12].It is well understood that the first-order behavior arrises from the coupling of the magnetic order parameter to soft electronic particle-hole fluctuations, giving rise to non-analytic terms in the free energy [13][14][15][16]. Because of this interplay between low-energy quantum fluctuations, metallic FMs are very susceptible towards the formation of incommensurate magnetic [17], spin nematic [14] or modulated superconducting states [18]. This spatial modulation is associated with deformations of the Fermi surface that enhance the phase space for low energy particle-hole fluctuations. The phase reconstruction can therefore be viewed as a fermionic quantum orderby-disorder effect, which can be studied systematically by self-consistently calculating fluctuations around a whole class of possible broken-symmetry states [19][20][21].The coupling to electronic quantum fluctuations can also have counter-intuitive effects upon the direction of the magnetic order parameter. A notable example is the partially ordered phase of the helimagnet MnSi, in which the spiral ordering vector rotates away from the lattice favored directions [22,23]. Similar effects are possible in homogenous itinerant FMs. This is suggested by recent experiments that show unusual ordering of magnetic moments along hard magnetic directions [11,12].The first example is YbRh 2 Si 2 , which is a prototypical system for studying antiferromagnetic quantum criticality, but exhibits strong FM fluctuations [24]. In...

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Tricritical Point and Wing Structure in the Itinerant FerromagnetUGe2

Cited by 157 publications

References 34 publications

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

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

Universality and critical behavior at the critical endpoint in the itinerant-electron metamagnet UCoAl

Fluctuation-Driven Magnetic Hard-Axis Ordering in Metallic Ferromagnets

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