Magnetic interplay of Mn and Yb sites in YbMn2Si2 – crystal field and electronic structure studies

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Australian Institute of Physics
The layered RT2X2 series of compounds (R = rare-earth, T = 3d, 4d transition metal, X = Si, Ge) of bct ThCr2Si2–type structure (I4/mmm) is one of the most widely studied systems in condensed matter and materials science [e.g. 1]. Yb-based compounds are of particular interest with their intermediate valence character leading to a wide range of unusual physical and magnetic properties. Following investigation of the magnetic dynamics of YbT2Si2 for non-magnetic T = Ni, Co and Fe [2], we investigated YbMn2Si2 to explore the interaction between the crystal field excitations of Yb atoms and the magnetic ordering of Mn atoms by thermal inelastic neutron scattering [3]. Here we extend these studies of crystal field splittingof YbMn2Si2 to high resolution (800 μeV and a dynamic range of ~14 meV; PELICAN, OPAL) over the temperature range 5-65 K. The results have been analysed in terms of a crystal field model above and below TN2, the temperature at which the collinear antiferromagnetic structure AFil (TN1 = 526(4) K > T > TN2 = 32(2) K) transforms to the low temperature structure below TN2 in which the magnetic cell is doubled along the c-axis [e.g. 3]. Density functional theory with a Hubbard correction (DFT+U method) was used to model YbMn2Si2. A key finding is that the 4f electron Ueffparameter in this compound needs to be negative to stabilise the trivalent state of YbMn2Si2 with the strength of these interactions reflected in contraction of the lattice parameter.
Manganese, Ytterbium, Crystal field, Transition metals, Silicon, Germanium, Materials, Valence, Temperature range 0013-0065 K, Crystal lattices
Mole, R. A., Cortie, D. L., Hofmann, M., Wang. J., Yu, D. Wang, X., & Campbell, S. J. (2018). Magnetic interplay of Mn and Yb sites in YbMn2Si2 – crystal field and electronic structure studies. Paper presented to the 42nd Annual Condensed Matter and Materials Meeting Charles Sturt University, Wagga Wagga, NSW 30th January – 2nd February, 2018, (pp. 81). Retrieved from: