Spin-fluctuation theory for weak itinerant-electron ferromagnets: revisited

Kaul, S. N.

doi:10.1088/0953-8984/11/39/315

Cited by 48 publications

(80 citation statements)

References 68 publications

(72 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…spin fluctuations). Examples of this behavior include the weak itinerant ferromagnets ZrZn 2 , Ni 3 Al and the highly renormalized paramagnets Ni 3 Ga and Sr 3 Ru 2 O 7 , 27,28,29,30,31 although the renormalizations in those materials are apparently stronger than in our measurements for BaCo 2 As 2 .…”

contrasting

confidence: 46%

Renormalized behavior and proximity ofBaCo2As2to a magnetic quantum critical point

et al. 2009

View full text Add to dashboard Cite

We report synthesis and single crystal measurements of magnetic, transport and thermal properties of single crystalline BaCo2As2 as well as first principles calculations of the electronic structure and magnetic behavior. These results show that BaCo2As2 is a highly renormalized paramagnet in proximity to a quantum critical point, presumably of ferromagnetic character and that BaFeNiAs2 behaves similarly. These results are discussed in relation to the properties of Ba(Fe,Co)2As2 and Ba(Fe,Ni)2As2, which are superconducting for low Co and Ni concentrations.

show abstract

contrasting

confidence: 46%

Renormalized behavior and proximity ofBaCo2As2to a magnetic quantum critical point

et al. 2009

View full text Add to dashboard Cite

show abstract

“…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…”

mentioning

confidence: 99%

“…Although not necessary [35], a convenient approximation, good near a QCP, is that χ −1 (0, 0) ≈ 0, that is, I ≈ 1/N (E F ). One can also use an expansion for χ 0 (q, ω), equivalent to Eq.…”

mentioning

confidence: 99%

Magnetism, critical fluctuations, and susceptibility renormalization in Pd

2004

View full text Add to dashboard Cite

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...

show abstract

“…The initial version of the SCR theory where zero-point SF were neglected successfully explained many properties of weak itinerant magnets including the Curie-Weiss behavior of the magnetic susceptibility [1,10]. The further version of the SCR theory partly incorporated zero-point SF and their temperature dependence [11,12]. However, the authors [11,12] used the same RPA arguments neglecting strong spin anharmonicity induced by zero-point effects.…”

Section: Introductionmentioning

confidence: 99%

Generalized theory of spin fluctuations in itinerant electron magnets: Crucial role of spin anharmonicity

Solontsov

2015

Journal of Magnetism and Magnetic Materials

View full text Add to dashboard Cite

a b s t r a c tThe paper critically overviews the recent developments of the theory of spatially dispersive spin fluctuations (SF) in itinerant electron magnetism with particular emphasis on spin-fluctuation coupling or spin anharmonicity. It is argued that the conventional self-consistent renormalized (SCR) theory of spin fluctuations is usually used aside of the range of its applicability actually defined by the constraint of weak spin anharmonicity based on the random phase approximation (RPA) arguments. An essential step in understanding SF in itinerant magnets beyond RPA-like arguments was made recently within the softmode theory of SF accounting for strong spin anharmonicity caused by zero-point SF. In the present paper we generalize it to apply for a wider range of temperatures and regimes of SF and show it to lead to qualitatively new results caused by zero-point effects.

show abstract

Spin-fluctuation theory for weak itinerant-electron ferromagnets: revisited

Cited by 48 publications

References 68 publications

Renormalized behavior and proximity ofBaCo2As2to a magnetic quantum critical point

Renormalized behavior and proximity ofBaCo2As2to a magnetic quantum critical point

Magnetism, critical fluctuations, and susceptibility renormalization in Pd

Generalized theory of spin fluctuations in itinerant electron magnets: Crucial role of spin anharmonicity

Contact Info

Product

Resources

About