Determination of the Crystal Field Levels in TmV2Al20
Reyner White 1, Wayne Hutchison 1, Gail Iles 2, Richard Mole 2, Sean Cadogan 1, Takahiro Namiki 3, and Katsuhiko Nishimura
3
1 School of Physical, Environmental and Mathematical Sciences, The University of New South Wales, Canberra, ACT, 2600, Australia
2 Australian Centre for Neutron Scattering, Australian Nuclear Science and Technology Organisation, Kirrawee DC, NSW, 2232, Australia
3 Graduate School of Science and Engineering, University of Toyama, Toyama, 930-8555, Japan
So called caged rare earth compounds of the RM Al20-type (R = lanthanide, M = transition metal) exhibit interesting physical and magnetic properties at low temperatures. For example PrV Al20 and PrTi Al20 show a quadrupolar Kondo effect [1] and superconductivity [2] brought about by the non-magnetic ground state and the cubic symmetry of the Pr3+site. In this work the compound TmV Al20, a hole analogue of PrV Al20has been investigated. Previous crystal field calculations based on specific heat and magnetisation [3] resulted in parameters of W = 0.5 K and x = -0.6 within the Lea, Leask and Wolf formalism [4]. However to match the experimental zero field specific heat near 0.5 K, an artificial broadening of the ground state was applied. To validate and clarify these results, we have carried out an inelastic neutron scattering experiment on the PELICAN time-of-flight spectrometer to determine the energy splitting between the crystal field levels. This has allowed a further refinement of the crystal field parameters to W = 0.42(1) K and x = -0.63(1). The very broad Lorentzian line shapes suggest strong 4f-conduction band electron coupling.
[1] A. Sakai and S. Nakatsuji, J. Phys. Soc. Jpn. 80, 6 (2011)
[2] M. Tsujimoto, Y. Matsumoto, T. Tomita, A. Sakai and S. Nakatsuji, Phys. Rev. Lett. 113, 26(2014) [3] Q. Lei, T. Namiki, Y. Isikawa, K. Nishimura and W.D. Hutchison, J.Phys. Soc. Jpn. 85, 3 (2016) [4] K.R. Lea, M.J.M. Leask and W.P. Wolf, J. Phys. Chem.Solids 23, 10 (1962)
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