Interplay between hybridisation gaps and unusual magnetic orders in Kondo semiconductors CeT₂Al₁₀ (T = Ru and Os)

ABSTRACT

Kondo semiconductors based on rare-earth elements possess a narrow gap in the renormalised density of states near the Fermi level. Their ground states remain nonmagnetic due to strong hybridisation of the 4f state with conduction bands. However, in the orthorhombic compounds CeT₂Al₁₀ (T = Ru, Os), opening of a hybridisation gap is followed by an antiferromagnetic (AFM) order at a rather high temperature T_N≅ 28 K. Our systematic studies of the effects of electron/hole doping on the magnetic and transport properties, electron tunnelling, and spin-gap formation revealed that the hybridisation gap is indispensable for the unusual AFM order. Under uniaxial pressure, T_N increases linearly as the orthorhombic b-axis parameter is decreased. Our findings support the model that a kind of charge-density wave developing along the b axis in the presence of the hybridisation gap induces the AFM order in these systems.

KEYWORDS:

• Kondo semiconductor
• hybridisation gap
• magnetic order
• electron tunnelling
• uniaxial pressure

Acknowledgements

Most of this article is based on works conducted by collaborating with S. Kimura, Y. Yamada, Y. Okada, K. Yutani, J. Kajino, H. Onimaru, A. Sugimoto, T. Ishiga, T. Yokoya, A F. Strigari, K. Chen, A. Severing, D. D. Khalyavin, A. D. Hillier, A. M. Strydom, A. Bhattacharya and J. W. Taylor. The authors acknowledge valuable discussions with K. Hanzawa, H. Tanida, T. Nishioka, Y. Yanagi, Y. Kuramoto and H. Yuan.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by Japan Society for the Promotion of Science [grant numbers JP26400363, JP15K05180, and JP16H01076].