Magnetic Properties of a Quantum Ferrimagnet: NiCu(pba)(D_2O)_3 . 2D_2O

TL;DR

This study investigates the magnetic properties of NiCu(pba)(D_2O)_3·2D_2O, revealing ferrimagnetic behavior and quantifying exchange interactions through susceptibility measurements and theoretical modeling.

Contribution

The paper provides experimental magnetic data and fits it to a ferrimagnetic Heisenberg chain model, determining key exchange and g-values for the first time in this compound.

Findings

Susceptibility increases monotonically with decreasing temperature.

Exchange constant J/k_B is 121 K.

Model accurately reproduces field dependence of susceptibility.

Abstract

We report the results of magnetic measurements on a powder sample of NiCu(pba)(D_2O)_3 \cdot 2D_2O$ (pba=1,3-propylenebis(oxamato)) which is one of the prototypical examples of an $S$=1/2 and 1 ferrimagnetic chain. Susceptibility($\chi$) shows a monotonous increase with decreasing temperature (T) and reaches a maximum at about 7 K. In the plot of $\chi T$ versus $T$, the experimental data exhibit a broad minimum and are fit to the $\chi T$ curve calculated for the ferrimagnetic Heisenberg chain composed of S=1/2 and 1. From this fit, we have evaluated the nearest-neighbor exchange constant $J/k_B=121 K$, the g-values of Ni$^{2+}$ and Cu$^{2+}$, $g_{Ni}$=2.22 and $g_{Cu}$=2.09, respectively. Applied external field dependence of $\chi T$ at low temperatures is reproduced fairly well by the calculation for the same ferrimagnetic model.