Abstract
We use the dynamic spin-fluctuation theory to study spin-density correlations in ferromagnetic metals above the Curie temperature. We calculate the spatial spin-correlation function, dynamic susceptibility and local magnetic moment. The dynamic susceptibility is related to the energy-integrated scattering cross-section (effective moment). Calculated effective and local moments of Fe and Ni are found in good agreement with results of polarized neutron scattering experiment over a wide temperature range. We find that short-range order remains up to distances of about 6 Å in Fe and 8 Å in Ni at TTC = 1.1 and slowly decreases with temperature.
Highlights
Polarized neutron scattering experiments and static spin fluctuation theories[1] support the existence of short-range order (SRO) in metals above the Curie temperature, but there is no agreement about the range of SRO
We use the dynamic spin-fluctuation theory[4] (DSFT) that takes into account both quantum nature and nonlocal character of the spin fluctuations without mapping of the itinerant-electron system onto an effective Hamiltonian with classical spins.[5,6]
In the DSFT the calculated effective moment for bcc Fe was found in good agreement with polarized neutron scattering experiments.[7,8,9]
Summary
Polarized neutron scattering experiments and static spin fluctuation theories[1] support the existence of short-range order (SRO) in metals above the Curie temperature, but there is no agreement about the range of SRO. We use the dynamic spin-fluctuation theory[4] (DSFT) that takes into account both quantum nature and nonlocal character of the spin fluctuations without mapping of the itinerant-electron system onto an effective Hamiltonian with classical spins.[5,6] In the DSFT the calculated effective moment for bcc Fe was found in good agreement with polarized neutron scattering experiments.[7,8,9] Here we calculate the spin correlator as a function of distance and temperature and effective moment as a function of wavevector and temperature for Ni. Calculation results are compared with experiment
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