Slow relaxation in a {Tb 2 Ba(a-fur) 8 } :N polymer with Ln = Tb(iii) non-Kramers ions

Bartolomé, E. ; Arauzo, A. (Universidad de Zaragoza) ; Luzón, J. ; Melnic, S. ; Shova, S. ; Prodius, D. ; Bartolomé, J. (Universidad de Zaragoza) ; Amann, A. ; Nallaiyan, M. ; Spagna, S.

Resumen: We report the synthesis, crystal structure and magnetic properties of a new heteronuclear polymeric complex based on non-Kramers Tb ions and carboxylic a-fur = C 4 H 3 OCOO ligands: {[Tb 2 Ba(a-fur) 8 (H 2 O) 4 ]·2H 2 O} n . The a-furoate ligands consolidate 1D zig-zag chains running along the c-axis, formed by Tb 2 dimers separated by Ba ions. Ab initio calculations, in combination with the fit of experimental data, predict that the single-ion magnetic ground state is highly anisotropic and consists of a quasi-doublet with a ¿ Tb /k B = 3.22 K gap, well separated from the next excited state, while the gap for the Tb 2 dimer is ¿ 2Tb /k B = 2.58 K. Static magnetization and heat capacity measurements show that, magnetically, the system can be modeled as dimers of non-Kramers Tb ions, coupled by an antiferromagnetic intradimer interaction J'*/k B = -1.6 K. Dipolar interactions couple the Tb ions in the dimer with their first neighbour ions along the chain, with J''*/k B = -0.15 K, and with the surrounding ions out of the chain, with maximum J'''*/k B = -0.03 K. Ac susceptibility measurements in H = 0 performed down to 50 mK temperatures have enabled us to observe slow relaxation of magnetization, with an Orbach-like activation energy of U/k B = 1.1 K. It is assigned to the sluggish response of the 3D spin system due to a short-range ordering, possibly enhanced by the presence of disorder caused by defects in the polymeric chains. Under the application of a magnetic field, the system slowly relaxes by two distinct direct processes, strongly affected by a phonon bottleneck effect. We discuss the different relaxational phenomenology of the new complex in comparison with that of the isostructural {[Dy 2 Ba(a-fur) 8 (H 2 O) 4 ]·2H 2 O} n , differing only in the Kramers nature of the ions, and the mononuclear {Ln(a-fur) 3 (H 2 O) 3 } n (Ln = Tb, Dy) complexes, previously reported.

Idioma: Inglés

DOI: 10.1039/c8dt05044a

Año: 2019

Publicado en: Dalton Transactions 48, 15 (2019), 5022-5034
ISSN: 1477-9226

Factor impacto JCR: 4.174 (2019)

Categ. JCR: CHEMISTRY, INORGANIC & NUCLEAR rank: 5 / 45 = 0.111 (2019) - Q1 - T1

Factor impacto SCIMAGO: 1.048 - Inorganic Chemistry (Q1)

Financiación: info:eu-repo/grantAgreement/ES/MINECO/MAT2014-53921-R
Financiación: info:eu-repo/grantAgreement/ES/MINECO/MAT2015-68200-C2-2-P
Financiación: info:eu-repo/grantAgreement/ES/MINECO/MAT2017-83468-R

Tipo y forma: Artículo (PostPrint)

Área (Departamento): Área Física Materia Condensada (Dpto. Física Materia Condensa.)