Evidence for Appearance of an Internal Field in the Ordered State of CeRu₂Al₁₀by µ⁺SR

Crystal-field ground state of the orthorhombic Kondo insulator CeRu2Al10

“…21 Also, the small moment of µ c CF = 0.38 µ B agrees well with the experimental findings for the ordered magnetic moment, [7][8][9]12 indicating that CEF effects are responsible for the small size of µ ord .…”

“…The Ce moments order antiferromagnetically along the c direction with a small ordered moment of µ ord ≈ 0.4 µ B . [7][8][9]12 The latest NMR data agree with this scenario. 13 Below T 0 inelastic neutron scattering (INS) experiments on a polycrystalline sample have found the existence of a spin gap of several meV, characterized by a magnetic mode with flat dispersion at about 8 meV.…”

“…[6][7][8][9]12,13 In fact, in the structure of CeRu 2 Al 10 (space group Cmcm) each Ce atom is situated in a polyhedral cage consisting of 16 Al and 4 Ru atoms, giving rise to very large Ce-Ce distances of more than 5Å.…”

“…17 We can further give a set of CEF parameters that satisfies XAS, susceptibility, and INS data, 10 and the resulting moments are in accordance with moments from magnetization measurements. 21 The fact that the CEFonly moment along c amounts to only µ c CF = 0.38 µ B implies that the small value of the ordered moment [7][8][9]12 can be explained solely with CEF effects. The absence of any temperature dependence in the XAS data up to 100 K confirms that the excitation at 8 meV in the inelastic neutron spectra 9 is not a CEF transition.…”

“…CeRu 2 Al 10 is a fairly new synthesized orthorhombic intermetallic compound 1,2 and has initiated a flurry of experimental and theoretical research activities since the discovery of its Kondo insulating properties in 2009. [3][4][5][6][7][8][9][11][12][13][14][15][16][17][18][19][20][21][22] The electrical resistivity shows a thermally activated behavior at elevated temperatures and has a more metallic like form several degrees below T 0 = 27 K where a phase transition occurs as revealed by specific heat measurements. 3,4 A large anisotropy is observed in the static susceptibility (χ a >χ c >χ b ) and along the easy axis the susceptibility is Curie-Weiss like above T 0 .…”