Crystal-field ground state of the orthorhombic Kondo insulator CeRu2Al10

Abstract

We have succeeded in establishing the crystal-field ground state of CeRu2Al10, an orthorhombic intermetallic compound recently identified as a Kondo insulator. Using polarization dependent soft x-ray absorption spectroscopy at the Ce M4,5 edges, together with input from inelastic neutron and magnetic susceptibility experiments, we were able to determine unambiguously the orbital occupation of the 4f shell and to explain quantitatively both the measured magnetic moment along the easy a axis and the small ordered moment along the c-axis. The results provide not only a platform for a realistic modeling of the spin and charge gap of CeRu2Al10, but demonstrate also the potential of soft x-ray absorption spectroscopy to obtain information not easily accessible by neutron techniques for the study of Kondo insulators in general.Comment: submitted to Physical Review B Rapid Communication

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“…Further the strong anisotropic behavior in the paramagnetic state of all three compounds reveals the presence of strong hybridization between 4f-and conduction electrons. Moreover, there is also a strong single ion anisotropy arising from the crystal field potential in T=Ru and Os [47,48]. Another difference appears in the resistivity of CeT 2 Al 10 (T=Os and Ru).…”

“…3), have generated considerable interest in both theoretical and experimental condensed matter physics [28,[29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48]. This interest arose due to the various interesting ground states observed in this family of Ce-compounds as well as their caged type crystal structure that is important for the enhanced thermoelectric properties.…”

Collapse of the Gd3+ ESR fine structure throughout the coherent temperature of the Gd-doped Kondo Semiconductor CeFeVenegas1, Garcia2, García3 et al. 2016Phys. Rev. B80100View full textAdd to dashboardCite

“…Differently from heavy fermions systems, in Kondo-insulators the heavy-electron band is completely filled and the chemical potential falls in the middle of the hybridization gap (half-filling condition [12]). This semiconducting state manifests when the pseudogap straddles the Fermi energy, and is subjected to many-body renormalizations, leading to a T-dependent reduction of its magnitude [1,[3][4][5][6][7][8][9][10][11][13][14][15][16][17]. Among new and interesting compounds with properties being related to this model are Ce-based filled skutterudites compounds [18].…”

“…Among the strongly correlated electron systems, several rare-earth compounds, known as hybridization gap semiconductors or Kondo-insulators/semiconductors, have recently attracted great interest [1][2][3][4][5][6][7][8][9][10][11]. Kondo-insulators belong to a class of strongly correlated materials that form a group of either nonmagnetic semiconductors with a narrow-gap or semimetals with tiny gaps.…”

Exploring small energy scales with x-ray absorption and dichroism

“…In a solid environment, the degeneracy of the rare earth 4f ground configuration is lifted by the crystal field in general, causing both an anisotropic 4f charge distribution and, in conjunction with spin orbit coupling, (single ion) magnetic anisotropy. Unraveling the crystal field induced level structure thus constitutes an essential part of understanding the low temperature physics and of establishing correlations between local 4f symmetry at low temperature on the one hand and macroscopic ground state properties on the other.In this respect, the usefulness of probing the 4f configuration with linear polarized soft x-rays [6] has been demonstrated for a variety of Ce compounds in recent years [7][8][9][10][11][12][13][14], allowing to settle several open issues, where other experiments left room for diverging interpretations. Its magnetic variants, x-ray magnetic linear and circular dichroism (XMLD, XMCD) constitute sensitive element and orbital specific probes of magnetic polarization and anisotropy [15][16][17][18][19][20].…”