On the Theory of Spin Fluctuations around the Magnetic Instabilities   <i>Effects of Zero-Point Fluctuations</i>

Ishigaki, Aya; Moriya, Tôru

doi:10.1143/jpsj.67.3924

Cited by 47 publications

(66 citation statements)

References 31 publications

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“…The Curie-Weiss-like behavior has been observed in the doped IFMs ZrZn 2 and Sc 3.1 In [17,19], but not in the archetypical 3D IAFM Cr, in which the magnetization increased on warming [28]. The magnetic susceptibility of Cr is in disagreement with the self-consistent renormalization (SCR) theory, which predicts Curie-Weiss-like behavior for both the 2D [29] and 3D [30] antiferromagnets.…”

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confidence: 89%

Quantum critical point in the Sc-doped itinerant antiferromagnet TiAu

et al. 2017

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confidence: 89%

Quantum critical point in the Sc-doped itinerant antiferromagnet TiAu

et al. 2017

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“…This can be done using the fluctuation-dissipation theorem along the lines suggested by Moriya [33] and elaborated by many authors (see, e.g., Refs. [34][35][36]), which states that for zero-point fluctuations…”

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confidence: 99%

Magnetism, critical fluctuations, and susceptibility renormalization in Pd

2004

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Some of the most popular ways to treat quantum critical materials, that is, materials close to a magnetic instability, are based on the Landau functional. The central quantity of such approaches is the average magnitude of spin fluctuations, which is very difficult to measure experimentally or compute directly from the first principles. We calculate the parameters of the Landau functional for Pd and use these to connect the critical fluctuations beyond the local-density approximation and the band structure.The physics and materials science of weak itinerant ferromagnetic metals and highly renormalized paramagnets near magnetic instabilities has attracted renewed theoretical interest. This is a result of recent discoveries of materials with highly non-conventional metallic properties, especially, non-Fermi liquid scalings, metamagnetic behavior, and unconventional superconductivity, in several cases co-existing with ferromagnetism. Discoveries in the last three years alone include the co-existing ferromagnetism and superconductivity of Unfortunately, although model theories have been put forth, there is still not an established material specific (first principles) theoretical understanding of these phenomena. One difficulty is the usual starting point for first principles theories, density functional theory (DFT) as implemented in the local density approximation (LDA). This already includes most spin degrees of freedom, including dynamical fluctuations, as evidenced by its formally exact description of the uniform electron gas as well as its well documented success in accurately describing a wide variety of itinerant magnetic materials. However, the electron gas, upon which most density functionals are built, is not near any critical point for densities relevant to the solid state, and furthermore the proximity to itinerant magnetism of a metal is an extremely non-local quantity, in particular depending on the electronic density of states at the Fermi level N (E F ). Therefore, the exact DFT, which by definition includes all fluctuations and describes the ground state magnetization exactly, is likely to be extremely nonlocal and probably nonanalytical for the materilas near a quantum critical point.On the other hand, the LDA, while providing a good description of most itinerant ferromagnets that are not near critical points, fails to include the soft critical fluctuations in the materials of interest here. Since fluctuations are generically antagonistic to ordering, the result is that magnetic moments and magnetic energies of weak itinerant ferromagnets near critical points are overestimated in the LDA, as opposed to LDA's failure to describe (as mentioned, this latter material shows a metamagnetic quantum critical point). The basic theoretical difficulty in correcting the LDA for these materials is that there is some unknown and possibly strongly material dependent cross-over in energy (and possibly non-trivially in momentum) separating quantum critical fluctuations, not included in the LDA, from the dynamical f...

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“…In our earlier work [10], information regarding the nature of the high frequency fluctuations was obtained from the T > 3 K spin-lattice relaxation and specific heat data (see Figure 11). Following Moriya's self consistent renormalization theory (SCR) for quantum spin fluctuations [22], we observed a linear variation of 1/T 1 T with χ The FM correlations inferred from heat capacity and NMR data are surprising given the negative CW temperature extracted from high temperature magnetization and susceptibility data.…”

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confidence: 74%

Competing interactions and magnetic frustration in Yb4LiGe4

et al. 2011

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We have studied polycrystalline Yb 4 LiGe 4 , a ternary variant of the R 5 T 4 family of layered compounds characterized by a very strong coupling between the magnetic and crystallographic degrees of freedom. The system is mixed valent, with non-magnetic Yb 2+ and magnetic Yb 3+ present, and is characterized by coexisting ferromagnetic and antiferromagnetic correlations. We present measurements of resistivity, AC-susceptibility, specific heat, and muon spin relaxation (μSR), below 1 K. The low temperature measurements suggest a transition to a mesoscopically inhomogeneous magnetically ordered state below 2 K characterized by fluctuations well below the ordering temperature. This unusual state is believed to result from the enhanced twodimensionality produced by Li substitution and frustration effects inherent in the Yb sub-lattice geometry.2

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On the Theory of Spin Fluctuations around the Magnetic Instabilities Effects of Zero-Point Fluctuations

Cited by 47 publications

References 31 publications

Quantum critical point in the Sc-doped itinerant antiferromagnet TiAu

Quantum critical point in the Sc-doped itinerant antiferromagnet TiAu

Magnetism, critical fluctuations, and susceptibility renormalization in Pd

Competing interactions and magnetic frustration in Yb4LiGe4

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