Neutron scattering measurement of crystalline-electric fields in magnesium rare-earth selenide spinels

D. Reig-I-Plessis, A. Cote, S. Van Geldern, R. D. Mayrhofer, A. A. Aczel, G. J. Macdougall

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9 Scopus citations

Abstract

The symmetry of local moments plays a defining role in the nature of exotic ground states stabilized in frustrated magnetic materials. We present inelastic neutron scattering (INS) measurements of the crystal electric field (CEF) excitations in the family of compounds MgR2Se4 (Râ{Ho,Tm,Yb}). These compounds form in the spinel structure, with the rare-earth ions comprising a highly frustrated pyrochlore sublattice. Within the symmetry constraints of this lattice, we fit both the energies and intensities of observed transitions in the INS spectra to determine the most likely CEF Hamiltonian for each material and comment on the ground-state wavefunctions in the local electron picture. In this way, we experimentally confirm MgTm2Se4 has a nonmagnetic ground state, and MgYb2Se4 has effective S=12 spins with g =5.188(79) and g =0.923(85). The spectrum of MgHo2Se4 indicates a ground-state doublet containing Ising spins with g =2.72(46), though low-lying CEF levels are also seen at thermally accessible energies E=0.591(36), 0.945(30), and 2.88(7) meV, which can complicate interpretation. These results are used to comment on measured magnetization data of all compounds and are compared to published results on the material MgEr2Se4.

Original languageEnglish
Article number114408
JournalPhysical Review Materials
Volume3
Issue number11
DOIs
StatePublished - Nov 12 2019

Funding

This work was sponsored by the National Science Foundation, under Grant No. DMR-1455264-CAR. D.R. further acknowledges the partial support of the US DOE, Office of Science, Office of Workforce Development for Teachers and Scientists, Office of Science Graduate Student Research (SCGSR) program. The SCGSR program is administered by the Oak Ridge Institute for Science and Education for the DOE under Contract No. DE-AC05-06OR23100. R.D.M. acknowledges the support of the Research Experience for Undergraduates program funded by the NSF under Grant No. 1659598. Synthesis and magnetization measurements were carried out in the Materials Research Laboratory Central Research Facilities at the University of Illinois. X-ray scattering measurements were performed at the Center for Nanophase Materials Sciences at Oak Ridge National Laboratory. A portion of this work used resources at the Spallation Neutron Source, which is a DOE Office of Science User Facility operated by Oak Ridge National Laboratory.

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