Magnetic phase transitions in the triangular-lattice spin-1 dimer compound K2Ni2(SeO3)3

TL;DR

This study investigates magnetic phase transitions in the triangular-lattice spin-1 dimer compound K2Ni2(SeO3)3 through experiments and simulations, revealing a two-step transition influenced by magnetic anisotropy and field direction.

Contribution

It introduces a detailed model of the magnetic interactions in K2Ni2(SeO3)3 and uncovers the nature of field-induced phase transitions in this geometrically frustrated system.

Findings

Identification of intra- and inter-dimer exchange interactions

Observation of a two-step magnetic phase transition under c-axis field

Explanation of phase diagram differences due to magnetic anisotropy

Abstract

In our study, we conduct magnetization and heat capacity measurements to investigate field induced magnetic phase transitions within the newly synthesized compound K2Ni2(SeO3)3, a spin-1 dimer system arranged on a triangular lattice. From our first-principles simulations, we determine that the spin system in K2Ni2(SeO3)3 can be represented as a two-dimensional triangular-lattice spin-1 dimer model, including an intra-dimer exchange of J1 = 0.32 meV, an inter-dimer exchange of J2 = 0.79 meV, and an easy-axis anisotropy of D = 0.14 meV. The presence of easy-axis magnetic anisotropy explains the distinct magnetic phase diagrams observed under c-axis directional and in-plane magnetic fields. Notably, our investigation unveils a two-step phase transition with the magnetic field aligned with the c direction. Our findings yield valuable insights into the magnetic phase transitions inherent to geometrically frustrated magnetic systems featuring dimer structures.