The frequency- and wave-vector-dependent spin response function is calculated for a Heisenberg ferromagnet using the mode-coupling theory. Results are presented for the critical and paramagnetic regions. The work is motivated largely by recent, high-resolution neutron spectroscopy studies of EuO and EuS. In view of this, the Heisenberg model used incorporates nearest- and next-nearest-exchange interactions between spins on a face-centered-cubic lattice. The coupled-mode theory is shown to be successful in describing the measurements. Additional features are predicted as possible subjects of future experimental work. We present a review of various derivations of mode-coupling equations and demonstrate the equivalence of some prescriptions. The question of incorporating an external magnetic field in the theory is addressed, and we conclude that readily attainable fields have a minimal effect on the spin dynamics.

Critical and paramagnetic spin fluctuations in Heisenberg magnets / A. Cuccoli; S.W. Lovesey; V. Tognetti. - In: PHYSICAL REVIEW. B, CONDENSED MATTER. - ISSN 0163-1829. - STAMPA. - 39:(1989), pp. 2619-2631. [10.1103/PhysRevB.39.2619]

Critical and paramagnetic spin fluctuations in Heisenberg magnets

CUCCOLI, ALESSANDRO;TOGNETTI, VALERIO
1989

Abstract

The frequency- and wave-vector-dependent spin response function is calculated for a Heisenberg ferromagnet using the mode-coupling theory. Results are presented for the critical and paramagnetic regions. The work is motivated largely by recent, high-resolution neutron spectroscopy studies of EuO and EuS. In view of this, the Heisenberg model used incorporates nearest- and next-nearest-exchange interactions between spins on a face-centered-cubic lattice. The coupled-mode theory is shown to be successful in describing the measurements. Additional features are predicted as possible subjects of future experimental work. We present a review of various derivations of mode-coupling equations and demonstrate the equivalence of some prescriptions. The question of incorporating an external magnetic field in the theory is addressed, and we conclude that readily attainable fields have a minimal effect on the spin dynamics.
39
2619
2631
A. Cuccoli; S.W. Lovesey; V. Tognetti
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2158/360864
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