Open AccessDirect observation of paramagnetic spin fluctuations in LaFe13−xSix
Author(s) -
Tom Faske,
I. Radulov,
Markus Hölzel,
Oliver Gutfleisch,
Wolfgang Donner
Publication year - 2019
Publication title -
journal of physics. condensed matter
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.908
H-Index - 228
eISSN - 1361-648X
pISSN - 0953-8984
DOI - 10.1088/1361-648x/ab5a99
Subject(s) - condensed matter physics , paramagnetism , magnetization , curie temperature , scattering , neutron diffraction , magnetic susceptibility , neutron scattering , spin (aerodynamics) , magnetostriction , phase transition , magnetic field , materials science , diffraction , physics , ferromagnetism , quantum mechanics , optics , thermodynamics
Spin fluctuations are a crucial driving force for magnetic phase transitions, but their presence usually is indirectly deduced from macroscopic variables like volume, magnetization or electrical resistivity. Here we report on the direct observation of spin fluctuations in the paramagnetic regime of the magnetocaloric model system LaFe 11.6 Si 1.4 in the form of neutron diffuse scattering. To confirm the magnetic origin of the diffuse scattering, we correlate the temperature dependence of the diffuse intensity with ac magnetic susceptibility and x-ray diffraction experiments under magnetic field. Strong spin fluctuations are already observable at 295 K and their presence alters the thermal contraction behavior of LaFe 11.6 Si 1.4 down to the Curie temperature of the first-order magneto-structural transition at 190 K. We explain the influence of the spin fluctuation amplitude on the lattice parameter in the framework of the internal magnetic pressure model and find that the critical forced magnetostriction follows Takashi’s spin fluctuation theory for itinerant electron systems.