Muon spin relaxation and neutron scattering investigations of the noncentrosymmetric heavy-fermion antiferromagnet CeRhGe3

Abstract

The magnetic ground state of CeRhGe 3 has been investigated using magnetic susceptibility, heat capacity, neutron diffraction, muon spin relaxation (µSR), and inelastic neutron scattering (INS) techniques. Our µSR study clearly reveals the presence of two frequencies below T N2 = 7 K and three frequencies between 7 K and T N1 = 14.5 K, indicating long-range magnetic ordering of the Ce 3+ moment. The temperature dependence of the highest frequency follows a mean-field order parameter. Our powder neutron diffraction study at 1.5 K reveals the presence of magnetic Bragg peaks, indexed by the propagation vector k = (0, 0, 3/4) with the Ce 3+ magnetic moment ∼0.45(9) µ B along the c axis. INS studies at 18 K (i.e., above T N1 ) show the presence of two well-defined crystal-field (CEF) excitations at 7.5 and 18 meV. At 10 and 4.5 K, a very small increase has been observed in the CEF excitation energies. At 100 K, both CEF excitations broaden and a broad quasielastic component has also been observed. Further, the low-energy INS study reveals the presence of a nearly temperature-independent quasielastic linewidth between 16 and 60 K, which indicates a Kondo temperature T K = 12.6(3) K. The presence of well-defined CEF excitations in CeRhGe 3 suggests local moment magnetism and may explain the absence of pressure-induced superconductivity. Analyzing the INS data based on a CEF model, we have evaluated the CEF ground-state wave functions and ground-state moment. The observed small value of the ordered moment along the c axis, deduced from the neutron diffraction data, contrasts with the ab-plane moment direction predicted by the single-ion CEF anisotropy and indicates the presence of two-ion anisotropic magnetic exchange interactions, which govern the direction of the moment.

Evidence for a hybridization gap in noncentrosymmetricCeRuSi3

“…The value of γ is 62.5(1) mJ/mol K 2 for CeRuSi 3 compared to 6.5(1) mJ/mol K 2 for LaRuSi 3 . This is a moderate enhancement due to electronic correlations and is comparable to the values observed for the isostructural CeRhGe 3 [15] and CeCoGe 3 [23]. Both CeRhGe 3 and CeCoGe 3 order antiferromagnetically and INS measurements reveal well defined CEF levels.…”

“…Although inelastic neutron scattering (INS) investigations have been performed on several CeTX 3 compounds for (T = Co, Rh, or Ir; X = Si or Ge) [14][15][16], as far as we are aware there are no reports of such measurements on isostructural CeRuSi 3 . The aim of the present work is to investigate the magnetic INS response of CeRuSi 3 to probe the nature of the 4f electrons; that is, whether they display localized or itinerant behavior.…”

Muon spin rotation and neutron scattering study of the noncentrosymmetric tetragonal compoundCeAuAl3

“…It is interesting to mention that the INS spectra of CeAuAl 3 do not show any sign of CEF-phonon coupling, unlike that observed in CeCuAl 3 . Further, the overall CEF splitting of 25 meV observed in CeAuAl 3 is higher than the overall CEF splitting of ∼20 meV observed in CeCuAl 3 [23] and CeRhGe 3 [10].…”

“…Above the QCP, a very strong HF character will eventually reduce the T K , and these systems exhibit non-Fermi-liquid (NFL) properties [7][8][9]. * Corresponding author: devashibhai.adroja@stfc.ac.uk Cerium-based HF intermetallic compounds with the general formula CeTX 3 (1-1-3 stoichiometry, with T = transition metals and X = Si, Ge, and Al), have recently attracted considerable experimental and theoretical interest [10][11][12][13][14][15]. The reason is due to the discovery of many novel ground state properties in the tetragonal noncentrosymmetric crystal structure, such as unconventional superconductivity in CeTSi 3 , T = Ir and Rh, and CeCoGe 3 , at around QCP under pressure [16][17][18][19].…”

“…The observed three CEF excitations in CeCuAl 3 have been explained based on the CEF-phonon coupling model (called magnetoelastic coupling) [23]. In order to investigate whether or not the CEF-phonon coupling is also present in other members of the noncentrosymmetric compounds with the general formula CeTX 3 , we are currently investigating several compounds of this family using INS [10][11][12]23]. In the present paper, we have investigated the tetragonal CeAuAl 3 compound using various bulk characterization techniques, muon spin rotation (μSR), as well as using neutron scattering (both elastic and inelastic).…”