Tailoring magnetic nanocrystal superlattices by chemical engineering

Sudfeld, D.; Wojczykowski, Klaus; Hachmann, Wiebke; Jutzi, Peter; Reiss, Günter; Hütten, Andreas

doi:10.1063/1.1558235

Cited by 15 publications

(9 citation statements)

References 8 publications

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“…We present investigations on one ferrofluid consisting of Co-particles with o-dichlorobenzene (ODCB) as solvent. The ferrofluid was prepared using high-temperature solution-phase synthesis ( [1] and references herein). The particle radii derived from room temperature magnetization measurements can be fitted very well by a lognormal distribution.…”

Section: Methodsmentioning

confidence: 99%

Demagnetization experiments on frozen ferrofluids

Michele

Hesse

Bremers

et al. 2004

phys. stat. sol. (c)

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PACS 75.50.Mm, 75.75.+a The best way to achieve a virgin state of a magnetized sample is to heat it up to a temperature high enough to destroy every magnetic order and thereafter cooling it down in a zero magnetic field. This procedure is often not possible because high temperatures may cause irreversible changes in the sample's constitution e. g. by crystallization in amorphous systems. Because of magnetic history and memory effects it is difficult to measure the same initial magnetization curves after different demagnetizing procedures for materials consisting of nanoparticles with high Curie temperatur TC . Very often the demagnetization by alternating decreasing magnetic fields (AC demagnetization) is used instead. Ferrofluids offer the possibility to demagnetize the sample by heating it above the melting point of the liquid in zero external field. The brownian motion destroys any "frozen in" magnetic order and relieves single domain particles in the fluid. After zero field cooling the virgin state may be reproducibly achieved. We present an experimental study showing the influence of different demagnetization sequences on the initial magnetization curves in frozen ferrofluids. In this contribution we show the deviation between thermally demagnetized and AC demagnetized samples by substracting both initial curves from each other. We detect a "frozen in" pattern which shows the "steps" of the AC demagnetization sequences. In a further step we focus on the experimental determination of the switching field distribution (SFD) of the particles. We compare the SFD with a plot proposed by Thamm and Hesse (1996). ExperimentsMagnetization experiments were performed in a Quantum Design SQUID Magnetometer (MPMSR2) localized at the Physikalisch-Technische Bundesanstalt (PTB) Braunschweig, Germany. We present investigations on one ferrofluid consisting of Co-particles with o-dichlorobenzene (ODCB) as solvent. The ferrofluid was prepared using high-temperature solution-phase synthesis ([1] and references herein). The particle radii derived from room temperature magnetization measurements can be fitted very well by a lognormal distribution. The expectation value of the fitted log-normal distribution is approximately 1.6 nm and the standard deviation 0.5 nm. These values are in very good agreement with results from electron microscopy. For high resolution electron microscopy (HRTEM) the samples were prepared by dipping the electron transparent TEM carbon grids into the highly diluted ferrofluid. During this procedure the particles tend to self-organize and form a hexagonal superlattice of up to 1µm×1µm in size. The ODCB has a melting point of around 220 K. The further discussed measurements are all performed at 5 K which implies that the solution is frozen and the particles are fixed in space.

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Section: Methodsmentioning

confidence: 99%

Demagnetization experiments on frozen ferrofluids

Michele

Hesse

Bremers

et al. 2004

phys. stat. sol. (c)

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“…Fe-Co alloys are used in a variety of applications such as targeted drug delivery, cancer therapy [9,10], highfrequency power applications [11], magnetic-resonance imaging [12], electromagnetic EM-wave absorption [13,14], and magnetoelastic soft actuators [15]. The synthesis of Fe-Co through chemical synthesis techniques has been a subject of interest and attempted through sol-gel method [16], hydrogen reduction [17], thermal decomposition [18,19], thermolysis [20,21], borohydride reduction [22], coprecipitation [23], and alkalide reduction [24]. However, most of these methods have limitations like too many reactiondependent parameters [17], use of environmentally hazardous chemicals [25], and low saturation magnetization [23].…”

Section: Introductionmentioning

confidence: 99%

Facile route to preparation of Fe-Co microclusters with highly enhanced magnetic performances

Zhou

Liu

et al. 2014

Materials Letters

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“…in read-write heads of magnetic storage devices, electronic bearings, high-temperature space powder system, and microactuators [8][9][10][11]. Therefore much efforts such as radio frequency plasma torch [12][13][14][15], mechanical alloying [16][17][18][19][20][21], electrodeposition [22][23][24][25][26][27][28][29][30][31], co-sputtering deposition [32][33][34], solvothermal treatment [35], thermal decomposition [36][37][38][39][40], solution phase synthesis [41][42][43][44][45][46][47][48][49][50][51], chemical vapor condensation [52], and sonolysis in organic solvent [53,54] had been devoted to produce FeCo alloys nanostructures. Solution phase synthesis strategies for FeCo nanoparticles have adva...…”

Section: Introductionmentioning

confidence: 99%