INVESTIGADORES
CALVO Rafael
artículos
Título:
Gadolinium and neodymium citrates: Evidence for weak ferromagnetic exchange between gadolinium(III) cations
Autor/es:
BAGGIO, RF; RAFAEL CALVO; GARLAND, MT; PEÑA, O,; PEREC, M; RIZZI, AC
Revista:
INORGANIC CHEMISTRY
Editorial:
American Chemical Society, USA
Referencias:
Año: 2005 vol. 44 p. 8979 - 8987
ISSN:
0020-1669
Resumen:
A new lanthanide-citrate motif
of general formula [Ln(Hcit)(H2O)2.H2O]n
where Ln = Gd 1 and Nd 2 and Hcit3- = C(OH)(COO-)(CH2COO-)2,
has been synthesized hydrothermally from Ln2O3 and citric
acid at 100 °C
and characterized by elemental analysis, IR, TG-DTA, single-crystal X-ray
diffraction and magnetic measurements. The structures can be seen as ladder
chains along the a axis, with dinuclear Ln2O2 units
serving as steps and R-COO groups as uprights, which are connected by
H-bonds. The magnetic susceptibility between 2 and 300 K and the magnetization
at 2 K, as a function of magnetic field between 0 and 5 T were measured for
both compounds. By modeling the magnetic behavior of the Gd compound with a
dinuclear Hamiltonian HS = gmB(SA+SB).Bo - Jo SA.SB
(SA=SB=7/2), a ferromagnetic exchange interaction Jo = 0.039 cm-1
was evaluated between Gd ions situated at do
= 4.321 Å in dinuclear units bridged by two symmetry-related tridentate
carboxylate oxygens. The EPR spectrum of the Gd compound is discussed. The
temperature dependence of the susceptibility of the Nd compound is due to the
depopulation of the excited crystal field levels when the temperature
decreases. The magnetic field dependence of the magnetization of 2 is attributed to the ground state
Kramers'
doublet populated at 2 K. The g-factor
of this ground state doublet is calculated from the data and compared with
values for other compounds reported in the literature.