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| Articolul precedent |
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 949 0 |
 SM ISO690:2012BARTOLOME, Bartolome, ARAUZO, A., LUZON, Javier, MELNYK, Silvia, SHOVA, Sergiu, PRODIUS, Denis, BARTOLOME, Juan, AMANN, Andreas, NALLAIYAN, Manivannan, SPAGNA, Stefano. Slow relaxation in a {Tb 2 Ba(α-fur) 8 } :N polymer with Ln = Tb(iii) non-Kramers ions. In: Dalton Transactions, 2019, nr. 15(48), pp. 5022-5034. ISSN 1477-9226. DOI: https://doi.org/10.1039/c8dt05044a |
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  Dalton Transactions |
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| Numărul 15(48) / 2019 / ISSN 1477-9226 /ISSNe 1477-9234 | |
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| DOI:https://doi.org/10.1039/c8dt05044a | |
| Pag. 5022-5034 | |
| Rezumat | |
We report the synthesis, crystal structure and magnetic properties of a new heteronuclear polymeric complex based on non-Kramers Tb ions and carboxylic α-fur = C 4 H 3 OCOO ligands: {[Tb 2 Ba(α-fur) 8 (H 2 O) 4 ]·2H 2 O} n . The α-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 Δ Tb /k B = 3.22 K gap, well separated from the next excited state, while the gap for the Tb 2 dimer is Δ 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(α-fur) 8 (H 2 O) 4 ]·2H 2 O} n , differing only in the Kramers nature of the ions, and the mononuclear {Ln(α-fur) 3 (H 2 O) 3 } n (Ln = Tb, Dy) complexes, previously reported. |
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Dublin Core Export
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<dc:creator>Bartolome, E.</dc:creator>
<dc:creator>Arauzo, A.B.</dc:creator>
<dc:creator>Luzon, J.</dc:creator>
<dc:creator>Melnic, S.V.</dc:creator>
<dc:creator>Şova, S.G.</dc:creator>
<dc:creator>Prodius, D.N.</dc:creator>
<dc:creator>Bartolome, J.S.</dc:creator>
<dc:creator>Amann, A.</dc:creator>
<dc:creator>Nallaiyan, M.</dc:creator>
<dc:creator>Spagna, S.</dc:creator>
<dc:date>2019-03-04</dc:date>
<dc:description xml:lang='en'><p>We report the synthesis, crystal structure and magnetic properties of a new heteronuclear polymeric complex based on non-Kramers Tb ions and carboxylic α-fur = C <sub>4</sub> H <sub>3</sub> OCOO ligands: {[Tb <sub>2</sub> Ba(α-fur) <sub>8</sub> (H <sub>2</sub> O) <sub>4</sub> ]·2H <sub>2</sub> O} <sub>n</sub> . The α-furoate ligands consolidate 1D zig-zag chains running along the c-axis, formed by Tb <sub>2</sub> 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 Δ <sub>Tb</sub> /k <sub>B</sub> = 3.22 K gap, well separated from the next excited state, while the gap for the Tb <sub>2</sub> dimer is Δ <sub>2Tb</sub> /k <sub>B</sub> = 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 <sub>B</sub> = -1.6 K. Dipolar interactions couple the Tb ions in the dimer with their first neighbour ions along the chain, with J′′∗/k <sub>B</sub> = -0.15 K, and with the surrounding ions out of the chain, with maximum J′′′∗/k <sub>B</sub> = -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 <sub>B</sub> = 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 <sub>2</sub> Ba(α-fur) <sub>8</sub> (H <sub>2</sub> O) <sub>4</sub> ]·2H <sub>2</sub> O} <sub>n</sub> , differing only in the Kramers nature of the ions, and the mononuclear {Ln(α-fur) <sub>3</sub> (H <sub>2</sub> O) <sub>3</sub> } <sub>n</sub> (Ln = Tb, Dy) complexes, previously reported.</p></dc:description>
<dc:identifier>10.1039/c8dt05044a</dc:identifier>
<dc:source>Dalton Transactions 48 (15) 5022-5034</dc:source>
<dc:title>Slow relaxation in a {Tb 2 Ba(α-fur) 8 } :N polymer with Ln = Tb(iii) non-Kramers ions</dc:title>
<dc:type>info:eu-repo/semantics/article</dc:type>
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