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M Jagodič, S Gyergyek, Z Jagličić, D Makovec, Z Trontelj

Detection of irreversible fusion of iron oxide magnetic nanoparticles into single-domain clusters by magnetic measurements. M Jagodič, S Gyergyek, Z Jagličić, D Makovec, Z Trontelj. SLONANO2007, Ljubljana, Slovenia, 10–12 October 200 7. Introduction.

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M Jagodič, S Gyergyek, Z Jagličić, D Makovec, Z Trontelj

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  1. Detection of irreversible fusion of iron oxide magnetic nanoparticles into single-domain clusters by magnetic measurements M Jagodič, S Gyergyek, Z Jagličić, D Makovec, Z Trontelj SLONANO2007, Ljubljana, Slovenia, 10–12 October 2007

  2. Introduction • aggregation behavior of a ferrofluid  technical and • medical applications • method for determining the extent of aggregation! • aggregates (many particles) & clusters (few particles) • physical properties change: magnetic properties • bigger clusters  stronger interactions  aggregates  SLONANO2007, Ljubljana, Slovenia, 10–12 October 2007

  3. Introduction • The aim of our work: • the potential use of magnetic measurements for determining the extent of particle fusion • Which is the most evident magnetic measurement method for detecting the fusion of particles? SLONANO2007, Ljubljana, Slovenia, 10–12 October 2007

  4. Ferrofluid structure and measuring procedure • γ-Fe2O3 particles coated with oleic acid and dispersed in n-decane: • concentrated (45.6 wt%) – strong interactions • diluted (2.6 wt%) – no (or low) interactions • ZFC/FC susceptibility, M(H), AC susceptibility on zero field-frozen and field-frozen samples SLONANO2007, Ljubljana, Slovenia, 10–12 October 2007

  5. Results: TEM • as-prepared ferrofluid: 10.6 ±2.9 nm • zerofield-driedand field-driedferrofluidclustering and aggregate formation SLONANO2007, Ljubljana, Slovenia, 10–12 October 2007

  6. Results: ZFC/FC susceptibility • superparamagnetic behavior • concentrated samples: constant FC curves below Tpeak considerable inter-particle interactions SLONANO2007, Ljubljana, Slovenia, 10–12 October 2007

  7. Results: ZFC/FC susceptibility • diluted samples:Tpeak is not affected by the freezing procedure  no fusion of particles • concentrated samples:Tpeak shifts to lower T if thesample is field-frozen!? SLONANO2007, Ljubljana, Slovenia, 10–12 October 2007

  8. Results: M(H) measurements • average particle diameter obtained from Langevin fit: • ~50% increase in V SLONANO2007, Ljubljana, Slovenia, 10–12 October 2007

  9. Results: AC susceptibility • diluted samples: Arrhenius law SLONANO2007, Ljubljana, Slovenia, 10–12 October 2007

  10. Results: AC susceptibility • concentrated samples:Vogel-Fulcher law ~65% increase in V SLONANO2007, Ljubljana, Slovenia, 10–12 October 2007

  11. Conclusions • diluted samples: • ZFC/ZF, M(H), AC: no particle fusion • concentrated samples: • M(H), AC: increase in average particle size • ZFC/FC: no relevant information SLONANO2007, Ljubljana, Slovenia, 10–12 October 2007

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