Theory of Itinerant Ferromagnets Exhibiting Localized-Moment Behavior above the Curie Point

Wang, S. Q.; Evenson, William E.; Schrieffer, J. R.

doi:10.1103/physrevlett.23.92

Cited by 191 publications

(27 citation statements)

References 9 publications

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“…Finally, Schrieffer and coworkers [ 4 ] , in their calculation of the many-body partition function, have got explicit solutions which may be helpful in constructing the interaction function EI needed in the present formulation. However, their simplest static approximation, for the ground state, is equivalent to HF theory.…”

Section: Discussionmentioning

confidence: 98%

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Local moments, electron correlation and density functional theory

Stoddart

March

Wiid

2009

Int. J. Quantum Chem.

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In earlier work, the magnetism of pure metals has been discussed in terms of the total energy E as a functional of the densities p*(r) of electrons with upward and downward spins.In the present paper, the problem of local moment formation when a magnetic impurity such as Fe or Co is added to a non-magnetic metallic matrix such as Cu or A1 is considered. It is shown that at the heart of the theory is a one-body spin-dependent potential V,(r) which can be divided into four parts Vn(r) = p(r) + V(r) + Vc(r) + "V,(r). Here is the potential generating the bands of the matrix metal, with dispersion relation c(k) and Wannier function w(r). V(r) generates the impurity state, with energy cd and wave function + d , while Vc(r) denotes the coupling between this d-state and the bands. Finally, and most importantly, y,(r) represents the effects of electron correlations on the impurity site.Using this one-body potential, the density p,(r) can be calculated, in principle exactly, by summing the squares of the occupied orbitals of the potential V,(r). This spin density has three components. The first involves the square of the Wannier function w, with weight determined by parameters nu . The second involves the product of+d and w, with weight mu while the third comes from +$ , with weight 1,. The total energy E[p+ , p-] becomes a function of 1, , mu and nu . I t is shown that the Hartree-Fock solution of Anderson is readily regained solely from the dependence of the energy on 1,.The present work shows how the dependence of the total energy on m and n can be formally incorporated into the theory. The main effects can be described by changes in the self-energy in the Anderson solution, this becoming now spin-dependent. If, eventually, spin and charge densities could be measured around impurities having local moments, it is pointed out that the one-body potentials V,(r) could be obtained. Matrix elements of the one-body potential with respect to +d and w(r) then give direct information on electron correlation. A brief discussion of the relation of the present approach to the calculation of Schrieffer and coworkers of the many-body partition function is given.

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Section: Discussionmentioning

confidence: 98%

“…Because of the interest which has recently focussed on the work of Schrieffer and coworkers [4], we want finally to make contact with their work. We stress that, in the present formulation of the model, we have dealt only with the ground state.…”

Section: Many-body Partition Function Of Schrieffer and Coworkers [4]mentioning

confidence: 99%

Local moments, electron correlation and density functional theory

Stoddart

March

Wiid

2009

Int. J. Quantum Chem.

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“…This is essentially a consequence of the fact that mean-field states in Ref. 13 do not possess a correct spin symmetry. Strong fluctuations are therefore required to restore spin symmetry, leading to the Kondo resonance.…”

Section: Stationary States and A New Saddle Point For The Symmetry-almentioning

confidence: 99%

Physical properties of a new coherent state of the almost degenerate infinite-U lattice Anderson model

Tolpin

1992

J Low Temp Phys

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A new approach toward understanding the heavyfermion systems (HFS) within a framework of the almost degenerate lattice Anderson Hamiltonian in the Kondo regime is proposed. In the coherent low temperature regime operators in the effective Hamiltonian are found to belong to an SU(2J 4-3) dynamical algebra. A canonical transformation is employed to decouple the quasiparticle branches, thereby setting up the decoupling equation. It is found that this decoupling equation has a solution of the symmetry-altering type 1. The thermodynamic response functions and other quantities are calculated for this new state. This solution is a consequence of the degeneracy of the uncoupled f-orbitals. It is characterized by the interatomic hopping off-electrons, which produces the spin delocalization regime and with the renormalized f-level pinned close to the Fermi level. This is also found to be the source of the apparent spin compensation regime, which is accompanied by large enhancement of the thermodynamic response functions. In addition, the caiculated phase coherence length is found to be much greater than a lattice constant, thereby showing a many-body character of this new state. It is believed that this new state provides an accurate description of the heavy Fermion state at low temperatures. The stability conditions for the new regime are also discussed.

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“…This partition function is calculated as') i (29) using a coupling constant integration [3]. I n order to get explicit results from (28) we had to Fourier transform Z,[iL,] which gives (T 6[vi -.nL]),, but this seems to be not, tract'able.…”

Section: P~~~[ V I R Imentioning

confidence: 99%

On Functional Fourier Transformation for the Hubbard Model and Similar Models

Behn

Weller

1980

Physica Status Solidi (b)

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Describing spin t -electrons the particle number operators nil are replaced under the functional integral directly by c-numbers vi~(t) using a %functional instead of the Hubbard-Stratonovich transformation. The Green function of the Hubbard model is thus exactly represented as an averaged Green function of electrons moving in a stochastic potential U v i~( t ) .The probability distribution for the stochastic process v~ containing the many body aspect and the information about the j. -electrons is determined. The vi+(t) are only allowed to jump between 0 and 1 reflecting the property of Fermion particle number operators. This exact scheme can be interpreted as a dynamically generalized alloy analogy. Fur die Beschreibung der Spin t-Elektronen werden unter dem Funktionalintegral dieTeilchenzah1-operatoren ni; unmittelbar durch c-Zahlen v i~( t )ersetzt, indem ein 8-Funktional anstelle der Hubbard-Stratonovich-Transformation benutzt wird. Die Greensche Funktion fur das Hubbardmodell wird so exakt dargestellt als eine gemitteite Greensche Funktion fur Elektronen, die sich in einem stochastischen Potential Uvii(t) bewegen. Die Wahrscheinlichkeitsverteilung fur den stochastischen ProzeD vi, die den Vielteilchenaspekt und die Information fiber die 4 -Elektronen enthalt, wird bestimmt. Die v i i ( t ) diirfen nur zwischen 0 und 1 springen als Folge der Eigenschaft von Fermiteilchenzahloperatoren. Dieses exakte Schema kann als eine dynamische Verallgemeinerung der Legierungsanalogie interpretiert werden.

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Theory of Itinerant Ferromagnets Exhibiting Localized-Moment Behavior above the Curie Point

Cited by 191 publications

References 9 publications

Local moments, electron correlation and density functional theory

Local moments, electron correlation and density functional theory

Physical properties of a new coherent state of the almost degenerate infinite-U lattice Anderson model

On Functional Fourier Transformation for the Hubbard Model and Similar Models

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