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

We report on the low-temperature magnetic susceptibilities and specific heats of the isostructural spin-ladder molecular complexes L$_{2}$[M(opba)]_{3\cdot xDMSO$\cdot y$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.Comment: 13 pages, 15 figures, submitted to Phys. Rev.

A NdIIICuII molecular material with a honeycomb-like structure

International audienceThe first two-dimensional molecular material Nd(III)−Cu(II) has been synthesized by reaction in DMF of [Cu(opba)]2- and Nd3+. The compound {Nd2[Cu(opba)0.5(ox)]3·9DMF}·4.5DMF has been structurally characterized. Its crystalline structure can be described as the superposition of honeycomb-like molecular motifs. This material exhibits a quasi nonmagnetic ground state at low temperature

Nonmagnetic ground state in the molecular material Nd2[Cu (pba)]3 -23 H2O (pba = 1,3-propylenebis( oxamato ))

The crystal structure of Nd 2 [Cu{pba)b•23 H 2 O with pba= 1,3-propylenebis(oxamato) was first described two years aga. lt consists of tube-like motifs of the formula Nd 2 [Cu(pba)b{H 2 O) 9 and noncoordinated water molecules. Each Nd(III) ion is surrounded by three nearest-neighbor Cu(II) ions, and in turn each Cu(II) ion_is situated between two Nd(III) ions. The magnetic properties of the compound have been investigated. The magnetic susceptibility presents a rounded maximum around 2.5 K, and the product of the magnetic susceptibility and the temperature tends to zero as the temperature approaches absolute zero. This indicates that the ground state of the compound is quasinonmagnetic, which at a first view is quite an unexpected result. This situation is attributed to a compensation between the local magnetic moments of the two Nd(III) ions and the three Cu(III) ions at low temperature. This idea has been tested with a theoretical model in which the local Kramer's doublets for Nd(III) and Cu(II) interact antiferromagnetically. A compensation of the magnetic moments may be expected for a value of the ratio g d /9c u close to 1.73 g d and 9cu being the average values of the Zeeman factor for the ground Kramer's doublet of Nd(III) and Cu(II), respectively

Structure and magnetic properties of Ln2[Cu(opba)]3(DMSO)6(H2O).H2O compounds with Ln=La to Lu exhibiting ladder like molecular motifs

International audienc

Watching television in later life: a deeper understanding of TV viewing in the homes of old people and in geriatric care contexts

A secret among staff at nursing homes is that they are often ambivalent about old residents spending so much time watching TV since it is a common cultural perception that it makes the viewer passive. The purpose of this paper is to highlight the importance of reflecting on the TV viewing habits old people bring with them when they move into geriatric care. The findings are based on a study involving qualitative interviews and observations in two nursing home settings – urban and rural – of twenty persons between 82 and 100. The results confirm that TV viewing is far from a passive activity. Instead, it contributes to structuring daily life, to satisfying old peoples’ needs for reflection and contemplation and to remaining socially integrated. As such, TV viewing makes a significant contribution to their capacity to cope with disengagement in old age and can be used as a way of promoting communication and well-being in geriatric care