Pronounced 2/3 magnetization plateau in a frustrated $S$ = 1 isolated spin-triangle compound: Interplay between Heisenberg and biquadratic exchange interactions

TL;DR

This study synthesizes a new Ni(II) spin-triangle compound exhibiting a pronounced 2/3 magnetization plateau, driven by the interplay of Heisenberg and biquadratic exchanges, with experimental and theoretical evidence of a disordered, gapped quantum spin state.

Contribution

It introduces a novel Ni(II) spin-triangle compound and demonstrates the emergence of a 2/3 magnetization plateau due to combined exchange interactions, supported by experimental and theoretical analysis.

Findings

Robust 2/3 magnetization plateau observed between 7 and 20 T.

Absence of magnetic order or glassy states down to 60 mK.

Disordered ground state with gapped spin excitations.

Abstract

We report the synthesis and characterization of a new quantum magnet [2-[Bis(2-hydroxybenzyl)aminomethyl]pyridine]Ni(II)-trimer (BHAP-Ni3) in single-crystalline form. Our combined experimental and theoretical investigations reveal an exotic spin state that stabilizes a robust 2/3 magnetization plateau between 7 and 20 T in an external magnetic field. AC-susceptibility measurements show the absence of any magnetic order/glassy state down to 60 mK. The magnetic ground state is disordered and specific-heat measurements reveal the gapped nature of the spin excitations. Most interestingly, our theoretical modeling suggests that the 2/3 magnetization plateau emerges due to the interplay between antiferromagnetic Heisenberg and biquadratic exchange interactions within nearly isolated spin $S$ = 1 triangles.