Antiferromagnetic Dimers of Ni(II) in the S=1 Spin-Ladder Na_2Ni_2(C_2O_4)_3(H_2O)_2

TL;DR

This study synthesizes and characterizes a Ni(II) spin-ladder compound, revealing that an isolated dimer model accurately describes its magnetic behavior, supported by experimental measurements and quantum Monte Carlo calculations.

Contribution

It introduces a new Ni(II) spin-ladder compound and demonstrates that an isolated dimer model effectively explains its magnetic properties, supported by comprehensive experimental and computational analysis.

Findings

Magnetic exchange constant J=43 K along rungs

Single ion anisotropy D=11.5 K from ESR

Isolated dimer model fits magnetic data well

Abstract

We report the synthesis, crystal structure and magnetic properties of the S=1 2-leg spin-ladder compound Na_2Ni_2(C_2O_4)_3(H_2O)_2. The magnetic properties were examined by magnetic susceptibility and pulsed high field magnetization measurements. The magnetic excitations have been measured in high field high frequency ESR. Although the Ni(II) ions form structurally a 2-leg ladder, an isolated dimer model consistently describes the observations very well. The analysis of the temperature dependent magnetization data leads to a magnetic exchange constant of J=43 K along the rungs of the ladder and an average value of the g-factor of 2.25. From the ESR measurements, we determined the single ion anisotropy to D=11.5 K. The validity of the isolated dimer model is supported by Quantum Monte Carlo calculations, performed for several ratios of interdimer and intradimer magnetic exchange and taking into account the experimentally determined single ion anisotropy. The results can be understood in terms of the different coordination and superexchange angles of the oxalate ligands along the rungs and legs of the 2-leg spin ladder.