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Spin relaxation phenomena in two novel Nd SIMs

AuthorsArauzo, Ana B.; Bartolomé, Elena ; Luzón, Javier; Melnic, S.; Shova, S.; Prodius, D.; Nlebedim, Ikenna C.; Bartolomé, Fernando; Bartolomé, Juan
Issue Date2019
Citation7th European Conference on Molecular Magnetism (2019)
AbstractLanthanide based single-ion magnets (SIMs) have received increasing attention in the field of molecular magnetism because of their large magnetic moment and strong anisotropy. Research has been strongly focused in heavy Ln(III) ions, mainly Dy3+ and Tb3+, whereas the number of works dedicated to SIMs based on light lanthanide ions remains low. However, light Ln(III) ions such as Nd3+ are less critical and cheaper than heavy Ln(III) ions based on European Union and U.S. DOE assessments. Here we present the study of two novel Neodymium based molecular magnets of formula {[Nd(α-fur)3(H2O)2]·DMF}n (1) and {[Nd0.065La0.935(α-fur)3(H2O)3]}n (2), α-fur=C4H3OCOO. In (1) the furoate ligands, in bidentate bridging mode, consolidate zig-zag chains running along the a-direction. Compound (2) is a magnetically diluted complex of a bidentate polymeric chain along the b-axis. Ab initio calculations yielded the gyromagnetic factors gx*=0.52, gy*=1.03, gz*=4.41 for (1) and gx*=1.35, gy*=1.98, gz*=3.88 for (2), and predicted energy gaps of Δ/kB=125.5 K (1) and Δ/kB=58.8 K (2), showing that Nd(III) holds significant anisotropy in both compounds. Heat capacity, dc magnetization and ac susceptibility measurements agree with these predictions. Absence of slow relaxation at H=0 is attributed to the sizable transverse anisotropy component. It can also be attributed to either dipolar or exchange interactions, which would enhance quantum tunnelling probability. Under small external applied field of 80 Oe, two slow relaxation processes appear. A relaxation mechanism above 3 K is associated to a combination of Orbach process, with activation energy U/kB=121 K at 1.2 kOe for 1, Raman and direct processes. For complex 2 a smaller U/kB=61 K at 1.2 kOe is found, and the low-frequency process is quenched. The absence of Nd-Nd interaction in the magnetically diluted compound 2 reduces the direct process contribution to the relaxation time, resulting in longer times at low temperatures. The two new furoate-based complexes enlarge the still scarce family of Nd(III) based compounds. The energy barrier of compound 1 is the highest ever reported for a Nd complex.
DescriptionResumen del póster presentado a la 7th European Conference on Molecular Magnetism (ECMM), celebrada en Florencia (Italia) del 15 al 18 de septiembre de 2019.
Appears in Collections:(ICMA) Comunicaciones congresos
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