Quantum Griffiths Phase in the Weak Itinerant Ferromagnetic Alloy<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi>Ni</mml:mi><mml:mrow><mml:mn>1</mml:mn><mml:mo>−</mml:mo><mml:mi>x</mml:mi></mml:mrow></mml:msub><mml:msub><mml:mi mathvariant="bold">V</mml:mi><mml:mi>x</mml:mi></mml:msub></mml:math>

Ubaid-Kassis, Sara; Vojta, Thomas; Schroeder, Almut

doi:10.1103/physrevlett.104.066402

Cited by 111 publications

(176 citation statements)

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“…4A) is too strong to be attributed entirely to that of the quasi-particle mass, reflecting instead a ferromagnetic enhancement of the susceptibility that is echoed in the unusually strong divergence of χ ac (T) ∼ T −1.4 found for B = 0. By the same token, the distinctly different temperature dependencies of C/T and χ(T) also rules out the possibility of a Griffiths phase, where both would have the same critical exponents (14,(31)(32)(33).…”

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confidence: 99%

“…High pressure experiments evade the disorder that necessarily accompanies doping, but thus far only resistivity and susceptibility measurements have been reported. Complete experimental access is possible when doping is used to suppress T C → 0, but even small amounts of compositional inhomogeneity can obscure any intrinsic critical fluctuations of T C = 0 ferromagnetic transitions, resulting in interesting complications such as the Griffiths phase (12,13,14), as well as short ranged order, including spin glasses (15). Alternative ordered states that range from unconventional superconductivity in UGe 2 (16) and UCoGe (17), antiferromagnetic order in CeRu 2 Ge 2 (18), hidden order in URu 1−x Re x Si 2 (19), and spiral order in MnSi (20) may also emerge when ferromagnetism becomes sufficiently weak, potentially masking quantum critical fluctuations associated with the underlying T C = 0 ferromagnetic transition.…”

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confidence: 99%

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Quantum critical fluctuations in layered YFe ₂ Al ₁₀

Kim

Park

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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The absence of thermal fluctuations at T = 0 makes it possible to observe the inherently quantum mechanical nature of systems where the competition among correlations leads to different types of collective ground states. Our high precision measurements of the magnetic susceptibility, specific heat, and electrical resistivity in the layered compound YFe 2 Al 10 demonstrate robust field-temperature scaling, evidence that this system is naturally poised without tuning on the verge of ferromagnetic order that occurs exactly at T = 0, where magnetic fields drive the system away from this quantum critical point and restore normal metallic behavior.quantum criticality | ferromagnet | dynamical scaling T he interplay of competing interactions is responsible for the array of ground states that are possible in correlated electron systems. It is of particular importance to understand how one such ground state gives way to another when the system is tuned at temperature T = 0, without the complications of thermal fluctuations. Consequently, much interest has focused on quantum critical points (QCPs), where an ordered phase can be created by an infinitesimal modifications of pressure, composition, or field. The onset of ferromagnetic order is perhaps the simplest T = 0 phase transition, and indeed much experimental and theoretical effort has been directed toward understanding its essential features (1-6). It is generally believed that ferromagnetic order occurs at T = 0 via a discontinuous or first order transition, as is observed in the clean ferromagnets ZrZn 2 (7) and MnSi (8) under pressure. Disorder is known to render the ferromagnetic transition continuous, leading to the mean field behavior that is found when doping drives T C = 0 in Ni 1−x Pd x (9), Zr 1−x Nb x Zn 2 (10), and Nb 1−y Fe 2+y (11). More controversial is the possibility that strong quantum fluctuations, such as those that destabilize order in low-dimensional systems, may be significant near the T C = 0 ferromagnetic transition and perhaps may even destroy its first-order character (5). A complete experimental investigation of the critical phenomena and their scaling behaviors in a carefully selected system where disorder is minimal is needed to establish that quantum critical fluctuations are both present and relevant to the destabilization of ferromagnetic order.Progress toward obtaining this information has been painstaking, although a number of systems have been identified where the Curie temperature T C has been driven to zero. High pressure experiments evade the disorder that necessarily accompanies doping, but thus far only resistivity and susceptibility measurements have been reported. Complete experimental access is possible when doping is used to suppress T C → 0, but even small amounts of compositional inhomogeneity can obscure any intrinsic critical fluctuations of T C = 0 ferromagnetic transitions, resulting in interesting complications such as the Griffiths phase (12,13,14), as well as short ranged order, including spin glasses (15). Alterna...

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Quantum critical fluctuations in layered YFe ₂ Al ₁₀

Kim

Park

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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“…In recent, some experimental signatures related to quantum Griffiths singularity been reported [36][37][38][39][40][41]. On the microscopic level, this quenched disorder introduces large rare regions, which can locally ordered in one phase and further influence the scaling behavior.…”

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confidence: 99%

Observation of quantum Griffiths singularity and ferromagnetism at the superconducting LaAlO3/SrTiO3(110) interface

et al. 2016

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Diverse phenomena emerge at the interface between band insulators LaAlO 3 and SrTiO 3 , such as superconductivity and ferromagnetism, showing an opportunity for potential applications as well as bringing fundamental research interests. Particularly, the two-dimensional electron gas formed at LaAlO 3 /SrTiO 3 interface offers an appealing platform for quantum phase transition from a superconductor to a weakly localized metal. Here we report the superconductor-metal transition in superconducting two-dimensional electron gas formed at LaAlO3/SrTiO3(110) interface driven by a perpendicular magnetic field. Interestingly, when approaching the quantum critical point, the dynamic critical exponent is not a constant but a diverging value, which is a direct evidence of quantum Griffiths singularity raised from quenched disorder at ultralow temperatures. Furthermore, the hysteretic property of magnetoresistance was firstly observed at LaAlO 3 /SrTiO 3 (110) interfaces, which suggests potential coexistence of superconductivity and ferromagnetism.

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“…These data were reinterpreted in Ref. [10] in terms of a Griffiths phase for x > x c . The interpretation of the susceptibility required adding a Curie component that was attributed to the presence of frozen spin clusters.…”

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Preasymptotic Critical Behavior and Effective Exponents in Disordered Metallic Quantum Ferromagnets

Kirkpatrick

Belitz

2014

Phys. Rev. Lett.

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We determine the pre-asymptotic critical behavior at the quantum ferromagnetic transition in strongly disordered metals. We find that it is given by effective power laws, in contrast to the previously analyzed asymptotic critical behavior, which is valid only in an unobservably small region. The consequences for analyzing experiments are discussed, in particular ways to distinguish between critical behavior and Griffiths-phase effects.PACS numbers: 64.70. Tg, 05.30.Rt, 75.40.Cx, 75.40.Gb The ferromagnetic quantum phase transition in metals has received a lot of interest in recent years. In clean systems it is now well established that the transition is generically first order. This has been observed experimentally for ferromagnets as diverse as the d-electron metals MnSi and ZrZn 2 [1, 2], and various uranium-based compounds [3]. It is in sharp contrast to early theories that predicted a second-order transition with mean-field exponents for both clean and disordered quantum ferromagnets [4], but in excellent agreement with a theory that takes into account the coupling between the magnetization and soft or gapless fermionic excitations in metals [5,6]. Disordered systems, which include almost all magnets where the quantum phase transition is triggered by chemical composition, are not as well understood. Experimentally, continuous or second-order transitions have been observed in a variety of systems, but attempts to determine exponents have yielded very different results for different systems, and even for different analyses of the same system [7][8][9][10]. Theoretically, the same framework that predicts a first-order transition in clean systems predicts a second-order one in the presence of quenched disorder [11][12][13]. Again, the coupling of gapless excitations (in this case, diffusive particle-hole excitations) leads to strong deviations from the prediction of Hertz theory [14]. The asymptotic critical behavior is given by non-mean-field power laws modified by multiplicative log-normal terms. Comparisons between this asymptotic critical behavior and experimental results are overall not satisfactory. Another important development has been the study of quantum Griffiths effects that are expected to be present in systems with quenched disorder [15,16]. These are due to rare regions devoid of disorder, occur in a whole region in the phase diagram, and are characterized by non-universal power laws. The interplay between Griffiths-phase effects and critical phenomena is incompletely understood and makes the interpretation of experiments difficult, see the discussion at the end.The quantum critical point is difficult to determine experimentally, and the distance from it can be hard to control. As a result, the experimental situation is much more difficult than in the case of classical phase transitions. For the latter, it is known that in almost all cases an observation of the asymptotic critical behavior requires measurements over two decades or more in a region within less (in some cases substantially less) t...

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Quantum Griffiths Phase in the Weak Itinerant Ferromagnetic AlloyNi1−xVx

Cited by 111 publications

References 35 publications

Quantum critical fluctuations in layered YFe ₂ Al ₁₀

Quantum critical fluctuations in layered YFe ₂ Al ₁₀

Observation of quantum Griffiths singularity and ferromagnetism at the superconducting LaAlO3/SrTiO3(110) interface

Preasymptotic Critical Behavior and Effective Exponents in Disordered Metallic Quantum Ferromagnets

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Quantum Griffiths Phase in the Weak Itinerant Ferromagnetic AlloyNi1−xVx

Cited by 111 publications

References 35 publications

Quantum critical fluctuations in layered YFe 2 Al 10

Quantum critical fluctuations in layered YFe 2 Al 10

Observation of quantum Griffiths singularity and ferromagnetism at the superconducting LaAlO3/SrTiO3(110) interface

Preasymptotic Critical Behavior and Effective Exponents in Disordered Metallic Quantum Ferromagnets

Contact Info

Product

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Quantum critical fluctuations in layered YFe ₂ Al ₁₀

Quantum critical fluctuations in layered YFe ₂ Al ₁₀