Field-induced internal Fe and Ln spin reorientation in butterfly{Fe3LnO2}(Ln=Dy and Gd) single-molecule magnets

L. Badía-Romano, F. Bartolomé, J. Bartolomé, J. Luzón, D. Prodius, C. Turta, V. Mereacre, F. Wilhelm, A. Rogalev
2013 Physical Review B  
The intramolecular exchange interactions within the single-molecule magnet (SMM) "butterfly" molecule [Fe 3 Ln(μ 3 -O) 2 (CCl 3 COO) 8 (H 2 O)(THF) 3 ], where Ln(III) represents a lanthanide cation, are determined in a combined experimental [x-ray magnetic circular dichroism (XMCD) and vibrating sample magnetometer (VSM)] and theoretical work. Compounds with Ln = Gd and Dy, which represent extreme cases where the rare earth presents single-ion isotropic and uniaxial anisotropy, on one hand, and
more » ... with Ln = Lu and Y(III) as pseudolanthanide substitutions that supply a nonmagnetic Ln reference case, on the other hand, are studied. The Dy single-ion uniaxial anisotropy is estimated from ab initio calculations. Low-temperature (T 2.5 K) hard x-ray XMCD at the Ln L 2,3 edges and VSM measurements as a function of the field indicate that the Ln moment dominates the polarization of the molecule by the applied field. Within the {Fe 3 LnO 2 } cluster the Ln-Fe 3 subcluster interaction is determined to be antiferromagnetic in both Dy and Gd compounds, with values J Dy-Fe 3 = −0.4 K and J Gd-Fe 3 = −0.25 K, by fitting to spin Hamiltonian simulations that consider the competing effects of intracluster interactions and the external applied magnetic field. In the uniaxial anisotropic {Fe 3 DyO 2 } case, a field-induced reorientation of the Fe 3 and Dy spins from an antiparallel to a parallel orientation takes place at a threshold field (μ 0 H = 4 T). In contrast, in isotropic {Fe 3 GdO 2 } this reorientation does not occur.
doi:10.1103/physrevb.87.184403 fatcat:ssaq7pfcqbezdojwrry675wlma