Drastic changes in electronic properties of Kondo semiconductor CeRu2Al10 induced by Rh doping: Anisotropic transport properties in the antiferromagnetic ordered state

• Published in: Physical review. B 2016-10, Vol.94 (16), p.165137
• Main Authors: Tanida, H, Nohara, H, Nakagawa, F, Yoshida, K, Sera, M, Nishioka, T
• Format: Article
• Language: English
• Subjects: Alternating current; Anisotropy; Antiferromagnetism; Doping; Electron states; Fermi surfaces; Properties (attributes); Temperature dependence
• ISSN: 2469-9950; 2469-9969
• DOI: 10.1103/PhysRevB.94.165137

Electrical resistivity (ρ), thermopower, and specific heat measurements have been performed on the novel Kondo semiconductor Ce(Ru1−xRhx)2Al10 (x=0, 0.02, 0.03, and 0.05), which has been attracting a great deal of interest due to an unusual antiferromagnetic (AFM) order below T0, in order to clarify the Rh doping effect on the anisotropy of the electronic properties in the ordered state. In CeRu2Al10, ρ shows an anisotropic increase below T0 independently of the electric current direction. We propose the existence of two different mechanisms to explain the anisotropic increase of ρ. One is an isotropic charge gap which enhances ρ below T0 isotropically, although its origin is not known at present. The other is an anisotropic suppression of ρ which originates from the anisotropic c-f hybridization and is largest along the orthorhombic a axis. By the Rh doping, the anisotropic temperature dependence of ρ below T0 is drastically changed. For I∥b, the increase is almost completely suppressed and a metallic-like behavior is observed, whereas it is small and isotropic for I∥a and c. From these results, we propose that as a result of the destruction of the spin-gap excitation by the Rh doping, a metallic-like electronic state is formed along the b axis and the small isotropic charge gap is opened in the ac plane. By taking into account the present results and the still high T0 even in x=0.05, we conclude that the AFM order in the Rh-doped CeRu2Al10 should be viewed as unusual as the AFM order in CeRu2Al10 although the localized character of the Ce-4f electron is apparently enhanced by the Rh doping. We have also examined the evolution of the AFM ordered state from x=0 to x=0.05, where the AFM ordered moment (mAF) is aligned along the c axis in x=0 and a axis in x=0.05. From the results of those experiments in magnetic field, we have revealed that the spin reorientation from mAF∥c to mAF∥a takes place quite abruptly just at xc∼0.03, which could be related to the topology change of the Fermi surfaces.