Magnetic and thermal properties of 4f-3d ladder-type molecular compounds

TL;DR

This study investigates the magnetic and thermal behaviors of isostructural 4f-3d ladder-type molecular compounds at low temperatures, revealing magnetic ordering, interactions, and crystal field effects through experimental and modeling approaches.

Contribution

It provides new insights into the magnetic interactions and ordering phenomena in 4f-3d ladder compounds, highlighting the dominant intraladder interactions and the influence of crystal fields.

Findings

Cu complexes undergo magnetic order below 2 K

Gd$_{2}$Cu$_{3}$ exhibits ferromagnetic order

Strong crystal field effects influence Tb, Dy, and Ho complexes

Abstract

We report on the low-temperature magnetic susceptibilities and specific heats of the isostructural spin-ladder molecular complexes L$_{2}$[M(opba)]$_{3\cdot x$DMSO$\cdot y$H$_{2}$O, hereafter abbreviated with L$_{2}$M$_{3}$ (where L = La, Gd, Tb, Dy, Ho and M = Cu, Zn). The results show that the Cu containing complexes (with the exception of La$_{2}$Cu$_{3}$) undergo long range magnetic order at temperatures below 2 K, and that for Gd$_{2}$Cu$_{3}$ this ordering is ferromagnetic, whereas for Tb$_{2}$Cu$_{3}$ and Dy$_{2}$Cu$_{3}$ it is probably antiferromagnetic. The susceptibilities and specific heats of Tb$_{2}$Cu$_{3}$ and Dy$_{2}$Cu$_{3}$ above $T_{C}$ have been explained by means of a model taking into account nearest as well as next-nearest neighbor magnetic interactions. We show that the intraladder L--Cu interaction is the predominant one and that it is ferromagnetic for L = Gd, Tb and Dy. For the cases of Tb, Dy and Ho containing complexes, strong crystal field effects on the magnetic and thermal properties have to be taken into account. The magnetic coupling between the (ferromagnetic) ladders is found to be very weak and is probably of dipolar origin.