Abstract
In this publication, we report on the study of the magnetic anisotropy of the cubane type tetranuclear cluster of Ni(II), [Ni4(L)4(MeOH)4] (H2L = salicylidene-2-ethanolamine; MeOH = methanol), by the means of angular-resolved magnetometry and polarized neutron diffraction (PND). We show that better than other usual characterization techniques—such as electron paramagnetic resonance spectroscopy (EPR) or SQUID magnetometry—only PND enables the full determination of the local magnetic susceptibility tensor of the tetranuclear cluster and those of the individual Ni(II) ions and the antiferromagnetic pairs they form. This allows highlighting that, among the two antiferromagnetic pairs in the cluster, one has a stronger easy-axis type anisotropy. This distinctive feature can only be revealed by PND measurements, stressing the remarkable insights that they can bring to the understanding of the magnetic properties of transition metals clusters.
Highlights
One of the present challenges in the field of molecular magnetism consists in understanding how to have the magnetic anisotropy under control, in order to design SMMs with high blocking temperatures
This, requires the presence of a strong uniaxial magnetic anisotropy and, a good knowledge of the magneto-structural relationships at the molecular level [1,2] Side by side with numerous theoretical studies based on quantum calculations [3,4,5], such knowledge has been greatly improved by the use of experimental methods, such as electron paramagnetic resonance spectroscopy (EPR) [6] or, more recently, by angular-resolved or torque magnetometry [7,8]
Polarized neutron diffraction on single crystal provides a detailed mapping of the magnetic anisotropy inside the title [Ni4] cubane cluster, which would otherwise remain entirely inaccessible using any other technique, for instance magnetometry or EPR, in such a compound with two different molecular orientations in the cell
Summary
One of the present challenges in the field of molecular magnetism consists in understanding how to have the magnetic anisotropy under control, in order to design SMMs (single molecule magnets) with high blocking temperatures. This, requires the presence of a strong uniaxial magnetic anisotropy and, a good knowledge of the magneto-structural relationships at the molecular level [1,2] Side by side with numerous theoretical studies based on quantum calculations [3,4,5], such knowledge has been greatly improved by the use of experimental methods, such as electron paramagnetic resonance spectroscopy (EPR) [6] or, more recently, by angular-resolved or torque magnetometry [7,8]. Large single crystals (size 9–12 mm3) were the bis‐ obtained. The tube was inserted inside a HLC TK13 heating-block thermostat keeping the crystallization temperature constant.
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