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- Title
Magnetic properties and neutron spectroscopy of lanthanoid-{tetrabromocatecholate/18-crown-6} single-molecule magnets.
- Authors
Dunstan, Maja A.; Cagnes, Marina; Phonsri, Wasinee; Murray, Keith S.; Mole, Richard A.; Boskovic, Colette
- Abstract
Lanthanoid single-molecule magnets (Ln-SMMs) exhibit slow magnetic relaxation at low temperatures. This arises from an energy barrier to magnetisation reversal associated with the crystal field (CF) splitting of the Ln(III) ion. The magnetic relaxation is impacted by the interaction of the molecule with the crystal lattice, so factors including particle size and crystal packing can play an important role. In this work, a family of compounds of general formula [Ln(18-c-6)(NO3)(Br4Cat)]·X (Ln = La, Tb, Dy; 18-c-6 = 18-crown-6; Br4Cat2− = tetrabromocatecholate) has been studied by inelastic neutron scattering (INS) and magnetometry to elucidate the effects of crystal packing on the slow magnetic relaxation of the Tb(III) and Dy(III) compounds. The deuterated analogues [Ln(18-c-6-d24)(NO3)(Br4Cat)]·CH3CN-d3 (1-Ln D ; Ln = La, Tb, Dy) have been synthesised, with 1-Tb D and the diamagnetic analogue 1-La D measured by INS. The dynamic magnetic properties of 1-Tb D and 1-Dy D have also been measured and compared for two samples with different particle sizes. To probe packing effects on the slow magnetic relaxation, two new solvatomorphs of the hydrogenous compounds [Ln(18-c-6)(NO3)(Br4Cat)]·X (2-Ln : X = CH2Cl2; 3-Ln : X = 0.5 toluene) have been obtained for Ln = Tb and Dy. The CF splitting between the ground and first excited CF pseudo-doublets has been experimentally determined for 1-Tb D by INS, and strongly rare earth dependent and anharmonic lattice vibrational modes have also been observed in the INS spectra, with implications for slow magnetic relaxation. Dynamic magnetic measurements reveal significant particle-size dependence for the slow magnetic relaxation for 1-Tb D , while a previously reported anomalous phonon bottleneck effect in the 1-Dy D analogue does not change with particle size. Further dynamic magnetic measurements of 2-Ln and 3-Ln show that the slow magnetic relaxation in these Ln-SMMs is strongly dependent on lattice effects and crystal packing, which has implications for the future use of Ln-SMMs in devices. The family of compounds [Ln(18-c-6)(NO3)(Br4Cat)]·X (Ln = La, Tb, Dy; 18-c-6 = 18-crown-6; Br4Cat2− = tetrabromocatecholate; X = MeCN, CH2Cl2, toluene) has been studied by inelastic neutron scattering and magnetometry to elucidate the effects of crystal packing and particle size on the slow magnetic relaxation of the Tb(III) and Dy(III) analogues.
- Subjects
SINGLE molecule magnets; INELASTIC neutron scattering; NEUTRON spectroscopy; MAGNETIC properties; MAGNETIZATION reversal; MAGNETIC relaxation
- Publication
Australian Journal of Chemistry, 2022, Vol 75, Issue 8/9, p595
- ISSN
0004-9425
- Publication type
Article
- DOI
10.1071/CH21306