Magnetic and quadrupole coupling emerging in NdB with geometrically frustrated orthogonal antiferromagnetic dimer

Metoki, Naoto   ; Yamauchi, Hiroki   ; Hagihara, Masato   ; Watanuki, Ryuta*; Kawamura, Seiko   ; Kofu, Maiko*   ; Nakajima, Kenji   ; Matsuda, Masaaki*

Inelastic neutron scattering experiments were carried out to understand the unusual successive order in NdB with the frustrated Shatry-Sutherland (SS) lattice. The pseudo-quartet with and splits into four levels in the magnetically ordered states. The spectra can be explained with the on-site magnetic interaction , the coupling of with quadrupole , and the uniaxial crystalline electric field. The -electron states reproduce the temperature dependences of the in-plane moment which is the primary order parameter, and a weakly induced as the secondary order parameter. The magnetic-quadrupole coupling emerges and play essential role under the geometrical frustration, where the Heisenberg interactions are cancelled out.