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Magnetic behaviour of TbPc2 single-molecule magnets chemically grafted on silicon surface.

Mannini M, Bertani F, Tudisco C, Malavolti L, Poggini L, Misztal K, Menozzi D, Motta A, Otero E, Ohresser P, Sainctavit P, Condorelli GG, Dalcanale E, Sessoli R - Nat Commun (2014)

Bottom Line: Going beyond investigations focused on physisorbed SMMs, in this work the robust grafting of terbium(III) bis(phthalocyaninato) complexes to a silicon surface from a diluted solution is achieved by rational chemical design yielding the formation of a partially oriented monolayer on the conducting substrate.Here by exploiting the surface sensitivity of X-ray circular magnetic dichroism, we evidence an enhancement of the magnetic bistability of this SMM, in contrast to the dramatic reduction of the magnetic hysteresis that characterizes monolayer deposits evaporated on noble and ferromagnetic metals.Photoelectron spectroscopy investigations and density functional theory analysis suggest a non-innocent role played by the silicon substrate, evidencing the potentiality of this approach for robust integration of bistable magnetic molecules in electronic devices.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry 'Ugo Schiff' and INSTM RU, University of Firenze, via della Lastruccia 3-13, Sesto Fiorentino 50019, Italy.

ABSTRACT
Single-molecule magnets (SMMs) are among the most promising molecular systems for the development of novel molecular electronics based on spin transport. Going beyond investigations focused on physisorbed SMMs, in this work the robust grafting of terbium(III) bis(phthalocyaninato) complexes to a silicon surface from a diluted solution is achieved by rational chemical design yielding the formation of a partially oriented monolayer on the conducting substrate. Here by exploiting the surface sensitivity of X-ray circular magnetic dichroism, we evidence an enhancement of the magnetic bistability of this SMM, in contrast to the dramatic reduction of the magnetic hysteresis that characterizes monolayer deposits evaporated on noble and ferromagnetic metals. Photoelectron spectroscopy investigations and density functional theory analysis suggest a non-innocent role played by the silicon substrate, evidencing the potentiality of this approach for robust integration of bistable magnetic molecules in electronic devices.

No MeSH data available.


Bulk magnetic properties of TbPc2(OC11H21)8a) AC susceptibility measurements in zero field. b) Arrhenius plot of data extracted from AC measurements in zero field and in a 5kOe static field. c) Magnetisation curves as a function of the temperature recorded at a field sweeping rate of 50 Oe s−1.
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Figure 2: Bulk magnetic properties of TbPc2(OC11H21)8a) AC susceptibility measurements in zero field. b) Arrhenius plot of data extracted from AC measurements in zero field and in a 5kOe static field. c) Magnetisation curves as a function of the temperature recorded at a field sweeping rate of 50 Oe s−1.

Mentions: Magnetic characterisation, performed with standard AC and DC magnetometric techniques (Fig. 2, Supplementary Fig. 3) clearly indicates the SMM behaviour of the complex in its bulk phase. In zero static field the AC susceptibility vs temperature curves are characterised by a frequency dependent peak in the out-of-phase component occurring at relatively high temperatures, e.g. the maximum in χ” at 1 kHz is observed at 47 K, which well compares with those reported for similar homoleptic substituted TbPc2 systems.35 A more careful analysis of the frequency dependence of the AC susceptibility in a wide frequency range, 0.5 Hz - 10 kHz, was performed with the extended Debye model3 allowing to extract the relaxation time, τ and its distribution width through the empirical parameter, α (Supplementary Note 3). The temperature dependence of τ is shown in Fig. 2b. A linear behaviour in the ln(τ ) vs. 1/T plot is observed at zero static field in the high temperature regime, T> 35 K, providing the parameters τ0 = 5.5±0.7×10−12 s and Δ/kB=811±5 K for the best fit with the Arrhenius law, τ = τ0exp(Δ/kBT). The estimated energy barrier in the thermally activated process is smaller than that found for the crystalline phase of TbPc2 (965 K)35 but it is close to the value observed in similar conditions for amorphous unfunctionalised TbPc2 system (856 K)26, in agreement with the amorphous character of TbPc2(OC11H21)8 sample. Below 35 K the relaxation becomes temperature independent, indicating the onset of a tunnel mechanism of relaxation, with a significant increase of the width of the distribution of the relaxation times.


Magnetic behaviour of TbPc2 single-molecule magnets chemically grafted on silicon surface.

Mannini M, Bertani F, Tudisco C, Malavolti L, Poggini L, Misztal K, Menozzi D, Motta A, Otero E, Ohresser P, Sainctavit P, Condorelli GG, Dalcanale E, Sessoli R - Nat Commun (2014)

Bulk magnetic properties of TbPc2(OC11H21)8a) AC susceptibility measurements in zero field. b) Arrhenius plot of data extracted from AC measurements in zero field and in a 5kOe static field. c) Magnetisation curves as a function of the temperature recorded at a field sweeping rate of 50 Oe s−1.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4129938&req=5

Figure 2: Bulk magnetic properties of TbPc2(OC11H21)8a) AC susceptibility measurements in zero field. b) Arrhenius plot of data extracted from AC measurements in zero field and in a 5kOe static field. c) Magnetisation curves as a function of the temperature recorded at a field sweeping rate of 50 Oe s−1.
Mentions: Magnetic characterisation, performed with standard AC and DC magnetometric techniques (Fig. 2, Supplementary Fig. 3) clearly indicates the SMM behaviour of the complex in its bulk phase. In zero static field the AC susceptibility vs temperature curves are characterised by a frequency dependent peak in the out-of-phase component occurring at relatively high temperatures, e.g. the maximum in χ” at 1 kHz is observed at 47 K, which well compares with those reported for similar homoleptic substituted TbPc2 systems.35 A more careful analysis of the frequency dependence of the AC susceptibility in a wide frequency range, 0.5 Hz - 10 kHz, was performed with the extended Debye model3 allowing to extract the relaxation time, τ and its distribution width through the empirical parameter, α (Supplementary Note 3). The temperature dependence of τ is shown in Fig. 2b. A linear behaviour in the ln(τ ) vs. 1/T plot is observed at zero static field in the high temperature regime, T> 35 K, providing the parameters τ0 = 5.5±0.7×10−12 s and Δ/kB=811±5 K for the best fit with the Arrhenius law, τ = τ0exp(Δ/kBT). The estimated energy barrier in the thermally activated process is smaller than that found for the crystalline phase of TbPc2 (965 K)35 but it is close to the value observed in similar conditions for amorphous unfunctionalised TbPc2 system (856 K)26, in agreement with the amorphous character of TbPc2(OC11H21)8 sample. Below 35 K the relaxation becomes temperature independent, indicating the onset of a tunnel mechanism of relaxation, with a significant increase of the width of the distribution of the relaxation times.

Bottom Line: Going beyond investigations focused on physisorbed SMMs, in this work the robust grafting of terbium(III) bis(phthalocyaninato) complexes to a silicon surface from a diluted solution is achieved by rational chemical design yielding the formation of a partially oriented monolayer on the conducting substrate.Here by exploiting the surface sensitivity of X-ray circular magnetic dichroism, we evidence an enhancement of the magnetic bistability of this SMM, in contrast to the dramatic reduction of the magnetic hysteresis that characterizes monolayer deposits evaporated on noble and ferromagnetic metals.Photoelectron spectroscopy investigations and density functional theory analysis suggest a non-innocent role played by the silicon substrate, evidencing the potentiality of this approach for robust integration of bistable magnetic molecules in electronic devices.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry 'Ugo Schiff' and INSTM RU, University of Firenze, via della Lastruccia 3-13, Sesto Fiorentino 50019, Italy.

ABSTRACT
Single-molecule magnets (SMMs) are among the most promising molecular systems for the development of novel molecular electronics based on spin transport. Going beyond investigations focused on physisorbed SMMs, in this work the robust grafting of terbium(III) bis(phthalocyaninato) complexes to a silicon surface from a diluted solution is achieved by rational chemical design yielding the formation of a partially oriented monolayer on the conducting substrate. Here by exploiting the surface sensitivity of X-ray circular magnetic dichroism, we evidence an enhancement of the magnetic bistability of this SMM, in contrast to the dramatic reduction of the magnetic hysteresis that characterizes monolayer deposits evaporated on noble and ferromagnetic metals. Photoelectron spectroscopy investigations and density functional theory analysis suggest a non-innocent role played by the silicon substrate, evidencing the potentiality of this approach for robust integration of bistable magnetic molecules in electronic devices.

No MeSH data available.