Speaker
Dr
Françoise Damay
(LLB, France)
Description
Layered triangular antiferromagnet selenide AgCrSe2 (SG : R3m) has been investigated by means of elastic and inelastic neutron scattering, combined with electrical transport, Seebeck coefficient, magnetisation and heat conductivity (kappa) measurements, in the range 5 to 300 K. Below TN = 55 K [1], long-range magnetic ordering is identified, characterized by long-wavelength incommensurate antiferromagnetic cycloids running along [110], and rotating within the ab plane (k = e e 3/2). No structural transition is observed down to 1.5 K, in contrast with structural parent AgCrS2 [2]. Spin wave modelling of the inelastic scattering spectrum in the magnetically ordered phase leads to ferromagnetic and antiferromagnetic exchange interactions between nearest and next-nearest neighbours, respectively, with a weak antiferromagnetic interplane exchange. The most remarkable features of the excitation spectra are a 3 meV phonon with an anomalous temperature behaviour above 80 K, and the persistence of a magnetic signal up to 150 K (~ 3 TN). The presence of this low energy phonon is in agreement with the extremely low thermal conductivity of AgCrSe2, which is attributed to phonon scattering by Ag+ rattling ; on the other hand, the absence of any magnetic field effect (up to 9T) on kappa suggests the absence of any additional contribution to the heat conduction from magnons [3].
[1] Bongers, P. F. et al., Journal of Physics and Chemistry of Solids 29, 977 (1968)
[2] Damay, F., et al., Physical Review B 87, 134413 (2013)
[3] Hess, C., Eur. Phys. J. Special topics 151, 73 (2007)
Primary author
Dr
Françoise Damay
(LLB, France)
Co-authors
Dr
Antoine Maignan
(CRISMAT, France)
Dr
Christine Martin
(CRISMAT, France)
Dr
Erik Elkaim
(Synchrotron Soleil, France)
Dr
François Fauth
(Alba Synchrotron, Spain)
Mr
Marcel Brandlein
(Centre Microélectronique de Provence, France)
Dr
Ramzy Daou
(CRISMAT, France)
Dr
Stéphane Rols
(ILL, France)
Dr
Sylvain Petit
(LLB, France)
