Inelastic neutron scattering of YbMn2Si2 – magnetic interplay of Mn and Yb sites

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Australian Institute of Nuclear Science and Engineering
The layered RT2X2 series of compounds (R = rare-earth, T = 3d, 4d transition metal, X = Si, Ge) of tetragonal body centred ThCr2Si2 –type structure (I4/mmm) is one of the most widely studied systems in condensed matter and materials science [e.g. 1]. Among the RT2X2 family, Yb- and Eu-based intermetallics continue to attract strong scientific interest, mainly as a result of their intermediate valence character and the related wide range of unusual physical and magnetic properties [e.g. 2]. Having delineated the spectral features of YbMn2Si2 in the region of the layered antiferromagnetism from TN1 = 526(4) K to TN2 = 30(5) K [3], we have investigated the crystal field splitting of YbMn2Si2 by inelastic neutron scattering using PELICAN over the temperature range 5-65 K. The high resolution - 800 µeV and dynamic range ~14 meV -svailable at λ = 2.375 Å has enabled the additional excitations observed below TN2 – the temperature below which the magnetic cell is doubled along the c-axis - to be investigated in detail. The results have been interpreted in terms of a crystal field model in which Yb3+ ions have a unique environment above TN2 with the doubled magnetic cell below TN2 leading to inequivalent sites for the Yb3+ ions. The calculated excitation spectra show good agreement with the observed spectra both above and below TN2. In particular the low temperature model describes a molecular field with components in the x, y and z directions with the x and y components related to the significant contraction of ~ 0.1 % of the c lattice parameter at TN2.
Rare earth compounds, Intermetallic compounds, Transition elements, Magnetic properties, Crystal field, Neutron diffraction
Mole, R. A., Yu, D. H., Hofmann, M., Wang, J. L., & Campbell, S. J. (2016). Inelastic neutron scattering of YbMn2Si2 – magnetic interplay of Mn and Yb sites. Paper presented at 13th AINSE-ANBUG Neutron Scattering Symposium, Sydney, NSW, Australia, 29-30 November 2016.