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arXiv · 2601.16389

Realization of a triangular spin necklace in a verdazyl-based Ni complex

Itsuki Shimamura·Risa Yagura·Takanori Kida·Masayuki Hagiwara·Koji Araki·Yoshiki Iwasaki·Yuko Hosokoshi·Kenta Kimura·Hironori Yamaguchi
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Abstract

We successfully synthesized a verdazyl-based complex, ($m$-Py-V)$_3$[Ni(NO$_3$)$_2$], in which Ni$^{2+}$ ions and verdazyl radicals form a one-dimensional, triangular spin necklace consisting of spin-1/2 and spin-1 units. Molecular orbital calculations reveal strong antiferromagnetic (AF) interactions between inversion-related radical pairs that form spin-1/2 singlet dimers. The remaining verdazyl and Ni$^{2+}$ spins form frustrated triangular units, creating a distinctive spin network. Magnetic susceptibility and specific heat measurements identify a phase transition to an AF order. The application of magnetic fields suppresses the phase transition signal, suggesting field-induced decoupling of the spin-1 moments. Electron spin resonance measurements are used to evaluate the easy-axis anisotropy of spin-1, which may promote the AF order. This work provides a rare example of a geometrically frustrated quantum spin chain realized via molecular design, thereby offering a platform for exploring frustration-driven quantum phases in low-dimensional materials.

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Itsuki Shimamura, Risa Yagura, Takanori Kida, Masayuki Hagiwara, Koji Araki, Yoshiki Iwasaki, Yuko Hosokoshi, Kenta Kimura, Hironori Yamaguchi. 2026-01-23. Realization of a triangular spin necklace in a verdazyl-based Ni complex. https://doi.org/10.1103/mkr4-63fh

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