Dysprosium Triangles Showing Single‐Molecule Magnet Behavior of Thermally Excited Spin States

Abstract

Dedicated to Professor Dante Gatteschi on the occasion of his 60th birthdayThe study of paramagnetic metal-ion aggregates has been of increasing interest since the observation that such molecules can exhibit magnetic memory effects. [1][2][3] Termed singlemolecule magnets or SMMs, the important factors leading to such properties derive from the combination of a large ground-state spin and a large magnetic anisotropy of the Ising (easy-axis) type. Studies have largely been based on transition-metal compounds since they typically exhibit both of the aforementioned features. The incorporation of lanthanides into these complexes has been investigated to take advantage of the potentially large number of unpaired f-electrons available. [4][5][6][7] However, very little work has been done to date on purely lanthanide-based systems. [8,9] The origin of SMM behavior in lanthanide-containing compounds is more complicated than that of d-block transition-metal ions since there is likely to be a significant orbital component. In the lanthanide-containing phthalocyanine complexes reported in the literature the ligand environment induces a large splitting of the ground J manifold, whereas in SMMs large-spin ground states arising from magnetic interactions between the metal centers of the cluster can enhance the weaker single-ion

Field-induced internal Fe and Ln spin reorientation in butterfly{Fe3LnO2}(LnBadía-Romano1, Bartolomé2, Bartolomé3 et al. 2013Phys. Rev. B212140View full textAdd to dashboardCite

“…We denote below the J Ln-M interaction in terms of the real Ln spin, J Dy = 15/2 and S Gd = 7/2, respectively. Recently, in the dimer [Cr(phen) 2 (μ-MeO) 2 Dy-(NO 3 ) 4 ] · xMeOH (x = 2 − 2.73), 34 by means of XMCD measurements a very weak Dy-Cr interaction was found, J Dy-Cr /k B = −0.06(2) K. Moreover, in [Dy(hfac) 3 (H 2 O)-CrF 2 (py) 4 -Dy(hfac) 3 (NO 3 )] the transition from an antiparallel to a parallel orientation of the Cr moment with respect to the Dy one was also observed with the help of XMCD and SQUID techniques. In that case, in spite of the sample's being powdered, the negative contribution to the magnetization due to the Cr is directly observed for an applied field lower than 2 T. The Dy-Cr interaction in terms of real Dy spin (J Dy = 15/2) was found to be J Dy-Cr /k B = −0.25 K. Taking into account that the Cr(III) spin is S Cr = 3/2, a lower value with respect to the {Fe 3 DyO 2 } case J eff (J Dy = 15/2)/k B = −0.4 K, where the Fe 3 (III) spin S Fe 3 = 5/2 is quite reasonable.…”

“…Other estimations of Gd-Fe interaction in SMM clusters have been done by SQUID magnetometry. In a "butterfly"-type [Fe(III) 4 . 18 These values are similar to those found in the present Gd butterfly molecules, J Gd-Fe w = −0.15 and J Gd-Fe b = 0.15 K. 20 The triangular [Fe 2 Gd] trimer presents a stronger ferromagnetic Gd-Fe interaction, J Gd-Fe = 1.2(3) K, however, strong frustration effects take place.…”

“…[1][2][3][4][5] In addition, they provide a variety of new chemical and physical properties, such as the possibility of chemically inducing magnetic anisotropy and of exploiting intramolecular exchange interactions. Indeed, a number of lanthanide-based complexes showing SMM behavior have been reported.…”

“…[6][7][8][9] The synthesis of molecules combining the magnetic moment and relatively strong exchange interactions of 3d transition metals (M) with the anisotropy naturally provided by lanthanide (Ln) ions is especially promising. Several molecular clusters of this type have been reported, such as {Mn 4 Ln 4 }, 10 {Mn 12 Gd}, 11 and {Cr 4 Dy 4 }, 12 with Ln = heavy Ln's, and {Mn 11 Ln 2 }, 13,14 with Ln = light rare earths. It was found that, in particular, Dy(III) ions are very useful for introducing anisotropy into these molecules, 15 thus confirming the possibility of achieving increased anisotropy in the lanthanide-transition-metal molecular combination.…”

Synthesis, Crystal Structures, and Magnetic Properties of One-dimensional Lanthanide(III)-Octacyanomolybdate(V) Assemblies with 3,4,7,8-Tetramethyl-1,10-phenanthroline as a Blocking Ligand

“…The variable-field magnetic properties show that the magnetization monotonously increases with the external field and goes up to 6.44 Nµ B mol -1 at 7 T, indicating that the cyano-bridge also mediates the ferromagnetic interaction between Mo V and Dy III ions (1 + 5.23) Nµ B . 21 No increase of χ M T observed at low temperature like that of complex 2 implies that the ferromagnetic interaction is very weak relative to the depopulation of the Stark levels of the Dy III ion.…”