Bulletin of the American Physical Society
APS March Meeting 2014
Volume 59, Number 1
Monday–Friday, March 3–7, 2014; Denver, Colorado
Session T7: Focus Session: Magnetic Nanoparticles |
Hide Abstracts |
Chair: Xuemei May Cheng, Bryn Mawr College Room: 106 |
Thursday, March 6, 2014 11:15AM - 11:27AM |
T7.00001: Fabrication of FeCo Nanoparticles by Sonochemical Route Frank Abel, George Hadjipanayis, Elvira Bauer FeCo nanoparticles with high saturation magnetization are greatly needed for biomedical applications and for the fabrication of exchange-coupled nanocomposite magnets. The aim of this study is to synthesize crystalline FeCo nanoparticles with a magnetic saturation over 200 emu/g. The preparation of FeCo nanoparticles was done through ultra sonochemical decomposition of iron (II) chloride and cobalt (II) chloride in di-ethylene glycol with hydrazine hydrate as a reducing agent. Our research led to FeCo nanoparticles with a maximum saturation magnetization of 215 emu/g, and with a particle size in the range of 40 to 200 nm. The size of the particles was controlled by varying the concentration of the chlorides in relation to the solvent. Current efforts are focused to making smaller particles with a size below 40 nm. [Preview Abstract] |
Thursday, March 6, 2014 11:27AM - 11:39AM |
T7.00002: Synthesis of core-shell iron nanoparticles via a new (novel) approach Rakesh P. Chaudhary, Ali R. Koymen Carbon-encapsulated iron (Fe) nanoparticles were synthesized by a newly developed method in toluene. Transmission Electron Microscopy (TEM) and High Resolution Transmission Electron Microscopy (HRTEM) of the as prepared sample reveal that core-shell nanostructures have been formed with Fe as core and graphitic carbon as shell. Fe nanoparticles with diameter 11nm to 102 nm are encapsulated by 6--8 nm thick graphitic carbon layers. There was no iron carbide formation observed between the Fe core and the graphitic shell. The Fe nanoparticles have body centered cubic (bcc) crystal structure. The magnetic hysteresis loop of the as synthesized powder at room temperature showed a saturation magnetization of 9 Am$^{2}$ kg$^{-1}$. After thermal treatment crystalline order of the samples improved and hence saturation magnetization increased to 24 Am$^{2}$kg$^{-1}$. We foresee that the carbon-encapsulated Fe nanoparticles are biologically friendly and could have potential applications in Magnetic Resonance Imaging (MRI) and Photothermal cancer therapy. [Preview Abstract] |
Thursday, March 6, 2014 11:39AM - 11:51AM |
T7.00003: A DFT study of geometric, electronic, and magnetic properties of Fe$_{\mathrm{x}}$Au$_{\mathrm{113-X}}$ (x$=$23, 56, 90) core-shell nanoparticles Sampyo Hong, Talat Rahman We have performed density functional theory (DFT) calculations for Fe$_{\mathrm{x}}$Au$_{\mathrm{113-X}}$ (x$=$23, 56, 90) nanoparticles to find that these nanoparticles prefer the formation of core-shell structure and the Fe core of the nanoparticles maintains almost constant magnetic moment of $\sim$ 2.8 $\mu_{\mathrm{B}}$ regardless of the Fe content, which is 27{\%} enhancement from the bulk value, in agreement with previous studies. The local magnetic moment of Fe atoms are correlated with the local coordination of Fe atoms and the enhanced magnetic moment is a result of charge depletion from Fe atoms to Au atoms. We find that the more the depleted charge, the larger is the induced magnetic moment. This indicates that electron depletion is crucial for the enhancement of the induced magnetic moment for Fe atoms. The case of Fe$_{\mathrm{90}}$Au$_{\mathrm{23}}$ is interesting as only a partial Au shell can be formed owing to the lack of the sufficient number of Au atoms in the cluster. This core-shell structure is more stable than the segregated phase consisting of two Fe and Au nanoparticles. Segregation between Fe and Au phases may be driven by large surface energy mismatch and core stress, but another important factor for the formation of the core-shell structure could be low surface tension in the Fe-Au interface (i.e., strong Fe-Au interfacial interaction), which we attribute to the large charge transfer at the interface. Work supported in part by DOE grant DE-FG02-07ER46354. [Preview Abstract] |
Thursday, March 6, 2014 11:51AM - 12:03PM |
T7.00004: Magnetic switching behavior of magnetic multilayer deposited on nanospheres Jiyeong Gu, Russell Gleason, Xiaoyu Zou, Brian Flores Magnetic properties of the nanostructure are determined by different aspects of the nanostructures, such as, size, shape, and curvature, since these affect the magnetic domain configurations and eventually contribute to the magnetic reversal mechanism. We prepared the monolayer of nanospheres on the Si substrate as a template and deposited magnetic layers on top of the nanospheres. The thickness of the magnetic layers on the nanospheres varies along the nanosphere surface (curved surface). If the layer thickness is much less than the nanosphere diameter the caps of material are isolated from each other. This will isolate magnetic domains and suppress magnetic exchange interaction between neighboring spheres. Magnetic switching behavior among samples with the same thickness of magnetic layer but deposited on the different substrates, either directly on Si substrate or nanospheres of different diameters, was studied by Magneto Optical Kerr Effect measurement. Magnetic switching behaviors of those samples were very different. Images of SEM, AFM, and MFM were taken to examine the morphology of these films. Also, we tried to model the magnetic switching behavior of the nanocap multilayer structure using micromagnetic simulations. [Preview Abstract] |
Thursday, March 6, 2014 12:03PM - 12:15PM |
T7.00005: Magnetic order and fluctuations in Fe$_{3}$O$_{4}$ nanoparticles assemblies Karine Chesnel, Yanping Cai, Matea Trevino, Roger Harrison, Jared Hancock, Andreas Scherz, Alexander Reid Magnetite (Fe$_{3}$O$_{4})$ particles exhibit a superparamagnetic behavior when their sizes are in nanometer scale. We are interested in investigating the magnetic order and fluctuation dynamics in self-assemblies of such nanoparticles. We fabricate our Fe$_{3}$O$_{4}$ nanoparticles following various chemical routes (organic and inorganic). The particle sizes range from 5 nm to 50 nm We have studied the effect the particle's size on their structural and magnetic properties with X-ray-Diffraction (XRD) and Vibrating Sample Magnetometry (MFM). The 5nm particles were deposited on membrane where they self-assemble in a hexagonal lattice. We have studied the magnetic order in such assemblies using X -ray resonant magnetic scattering (XRMS) at the SSRL synchrotron facility. This unique technique, combined with X-ray Magnetic Circular Dichroism (XMCD), provide information about the spatial distribution of the particles and their magnetic order [1]. In addition, the use of coherent light at the SSRL beamline, combined with the application of magnetic field in-situ at different temperatures, allows for studying local magnetic disorder [2] and dynamics of fluctuations near the blocking temperature.\\[4pt] [1] J.B.Kortright et al., PRB 71, 012402 (2005)\\[0pt] [2] K. Chesnel et al., PRB 83, 054436 (2011) [Preview Abstract] |
Thursday, March 6, 2014 12:15PM - 12:27PM |
T7.00006: Magnetic Properties of Core/Shell Structured Iron/Iron-oxide Nanoparticles Dispersed in Polymer Matrix Zohreh Nemati Porshokouh, Hafsa Khurshid, Manh-Huong Phan, Hariharan Srikanth Iron-based nanoparticles (NPs) show interesting magnetic properties for a wide range of applications; however rapid oxidation of iron limits its practical use. Protecting iron with a thin layer of iron-oxide is a possible way to prevent oxidation, forming core/shell (CS) iron/iron-oxide. Due to the different diffusivity rates of the two materials, a gap appears between the core and shell after a period of time (Kirkendall effect), degrading the magnetic properties of the sample. We minimize the Kirkendall effect while retaining good magnetic properties of $\sim$12.5 nm CS iron/iron-oxide NPs by dispersing them into a polymer matrix. Magnetic measurements reveal that after a period of 3 months the blocking temperature (TB) of as-made CS NPs decreases from 107 K to 90 K. The change in TB marks the formation of a gap between the core and shell, which is also evident from HRTEM studies. By contrast, NPs dispersed in RP show no change in TB over the same time period. We repeated experiments with $\sim$10.5 nm CS NPs and the results are consistent. Our study shows the importance of dispersing CS NPs in polymers to preserve desirable magnetic properties for practical applications, ranging from RF sensors and microwave devices to bioengineering. [Preview Abstract] |
Thursday, March 6, 2014 12:27PM - 12:39PM |
T7.00007: Diameter Dependence of Magnetic Properties in Nanoparticle-Filled CNTs Kristen Stojak, Sayan Chandra, Hafsa Khurshid, Manh-Huong Phan, Hariharan Srikanth, Ester Palmero, Manuel V\'azquez In past studies we showed magnetic polymer nanocomposites (MPNCs) with ferrite nanoparticle (NP) fillers to be magnetically tunable when passing microwave signals through films under the influence of an external magnetic field. We extend this study to include NP-filled multi-walled carbon nanotubes (CNTs) of various diameter ($\sim$300nm, $\sim$100nm, $\sim$40nm) synthesized by a catalyst-free CVD method, where the outer diameter of the CNTs is determined by a porous alumina template. These high-aspect ratio magnetic nanostructures, with tunable anisotropy and tunable saturation magnetization, are of particular interest in enhancing magnetic and microwave response in existing MPNCs. CNTs with $\sim$ 300nm diameter have been uniformly filled with cobalt ferrite and nickel ferrite NPs ($\sim$7nm). NP-filled CNTs show an increase in blocking temperature of $\sim$40K, as well as an increase in relaxation time, $\tau_{0}$. The enhancement of these properties indicates that enclosing NPs in CNTs increases interparticle interactions. The magnetic properties are also tunable by varying the diameter of CNTs. Characterization was completed with XRD, TEM and Quantum Design PPMS, with VSM and ACMS options. [Preview Abstract] |
Thursday, March 6, 2014 12:39PM - 12:51PM |
T7.00008: Effect of surface coating and solvent interactions on magnetization of iron oxide nanoparticles Deniz Rende, Dannah Laguitan, Richard A. Harris, Nihat Baysal, Seyda Bucak, Diana-Andra Borca-Tasciuc, Rahmi Ozisik Magnetic iron oxide nanoparticles (MIONPs) are being widely used in various biological applications, and they are surface modified with surfactants to increase their biocompatibility or to prevent their agglomeration in various solvents. However, the surfactants interact with the surface atoms of the nanoparticles leading to the formation of a magnetically disordered layer, which in turn reduces the effective magnetic phase. The magnetic phase reduction can also be attributed to the interaction between the surfactant and the solvent. In the current study, the interactions between the surfactants and the suspension media were investigated to understand their effect on magnetization of MIONPs. The surfactant--suspension media interactions were altered by gradually changing the quality of the solvent ranging from good to poor. The saturation magnetization was used to determine the effective concentration of magnetic phase as a function of solvent quality. The difference between the VSM and actual iron oxide concentration indicates the reduction of magnetic phase of the magnetic core as a function of solvent quality. [Preview Abstract] |
Thursday, March 6, 2014 12:51PM - 1:03PM |
T7.00009: Anisotropy and shape of hysteresis loop of frozen suspensions of iron oxide nanoparticles in water Zoe Boekelheide, Cordula Gruettner, Cindi Dennis Colloidal suspensions of nanoparticles in liquids have many uses in biomedical applications. We studied approximately 50 nm diameter iron oxide particles dispersed in H$_2$O for magnetic nanoparticle hyperthermia cancer treatment. Interactions between nanoparticles have been indicated for increasing the heat output under application of an alternating magnetic field, as in hyperthermia.[1] Interactions vary dynamically with an applied field as the nanoparticles reorient and rearrange within the liquid. Therefore, we studied the samples below the liquid freezing point in a range of magnetic field strengths to literally freeze in the effects of interactions. We found that the shape of the magnetic hysteresis loop is squarer (higher anisotropy) when the sample was cooled in a high field, and less square (lower anisotropy) when the sample was cooled in a low or zero field. The cause is most likely the formation of long chains of nanoparticles up to 500 $\mu$m, which we observe optically. This increase in anisotropy may indicate improved heating ability for these nanoparticles under an alternating magnetic field. [1] C. L. Dennis et al, Nanotechnology 20, 395103 (2009) [Preview Abstract] |
Thursday, March 6, 2014 1:03PM - 1:15PM |
T7.00010: Study of the electric and magnetic properties of FeVO$_{4}$ and iron oxide nanoparticle composites Ehab Abdelhamid, Suvra Laha, Gavin Lawes FeVO$_{4}$ is a multiferroic material that exhibits antiferromagnetic phase transitions near 15 K and 22 K in bulk. It was found that magnetically driven ferroelectricity develops at the lower temperature transition. In order to explore the possibility of increasing the coupling of antiferromagnetic FeVO$_{4}$ to an applied magnetic field along with possible exchange bias effects, we study the ferroelectric and ferromagnetic properties of FeVO$_{4}$ and iron oxide nanoparticle composites. The nanoparticles were prepared in a single chemical co-precipitation reaction and then sintered. We used X-ray diffraction and electron microscopy to characterize the structure and morphology of the nanoparticles. We investigated the magnetic and ferroelectric properties, including the magnetoelectric coupling, using temperature and field dependent magnetic and dielectric measurements. [Preview Abstract] |
Thursday, March 6, 2014 1:15PM - 1:27PM |
T7.00011: Magnetic field, frequency and concentration dependent electromagnetic heating by magnetic nanoparticles Vikash Malik, Tanya Prozorov, Surya Mallapragada, Ruslan Prozorov Measurements of electromagnetic heating of magnetic nanoparticles subject to radio frequency high amplitude AC magnetic field provide important insigt into the fundamental physics of individual particles as well as their collective behavior. By using different frequencies and magnetic field amplitudes and comparing with the standard DC measurements performed using SQUID magnetometer, we were able to estimate transient coercivity and hysteresis of unrelaxed magnetic state of the nanoparticles. Moreover, comparing different types of nanoparticles (varying chemical composition, containing medium, particle concentration, shape, size and protective coating) we can discuss the influence of these parameters on the hysteretic performance and provide arguments toward optimization of these parameters for practical application, for example in hyperthermal treatment. This work was supported by the Department of Energy Office of Science, Basic Energy Sciences under Contract No. DE-AC02-O7CH11358. [Preview Abstract] |
Thursday, March 6, 2014 1:27PM - 1:39PM |
T7.00012: Magnetic hyperthermia and photothermal effect of functionalized Fe$_{3}$O$_{4}$ nanoparticles for biomedical applications Md Ehsan Sadat, Donglu Shi, David B Mast The heating of nanoparticle loaded tissue surrogates for potential applications in cancer therapy was achieved when the superparamagnetic Fe$_{3}$O$_{4}$ nanoparticles were subjected to either high frequency alternating (AC) magnetic fields or near infra-red (NIR) radiation. Four nanoparticles systems were studied, where each system was distinct in terms of the arrangement, surface modification and physical confinement of the Fe$_{3}$O$_{4}$ nanoparticles. It was observed that the thermal response of each nanoparticle system to AC magnetic fields was different and could be described in terms of linear response theory and by taking into account the dipole-dipole interaction for closely packed nanoparticle systems. It was also shown that the same nanoparticle systems could be effectively heated when illuminated with NIR radiation at 785 nm and 808 nm. The measured optical absorption and scattering of the Fe$_{3}$O$_{4}$ nanoparticle systems was analyzed in terms of Mie scattering theory. The overall results from this study clearly demonstrate that the temperature increase of Fe$_{3}$O$_{4}$ nanoparticle loaded tissue surrogate samples to therapeutic levels could be achieved using AC magnetic fields and NIR radiation. [Preview Abstract] |
Thursday, March 6, 2014 1:39PM - 1:51PM |
T7.00013: Probing magnetic properties of ferrofluids using temperature dependent magnetic hyperthermia studies Humeshkar Nemala, Jagdish Thakur, Vaman Naik, Ratna Naik Tuning the properties of magnetic nanoparticles is essential for biomedical and technological applications. An important phenomenon displayed by these nanoparticles is the generation of heat in the presence of an external oscillating magnetic field and is known as magnetic hyperthermia (MHT). The heat dissipation by the magnetic nanoparticles occurs via Neel relaxation (the flip of the internal magnetic moment of the nanoparticles) and Brownian relaxation (the physical rotation of the nanoparticles in the suspended media). Dextran coated iron oxide (Fe$_{\mathrm{3}}$O$_{\mathrm{4}})$ nanoparticles were synthesized using the co-precipitation method and characterized using XRD, TEM and DC magnetometry measurements. Roughly spherical in shape the particles have an average size of 13nm and a saturation magnetization of 65 emu/g. The MHT properties of these nanoparticles suspended in a weakly basic solution (ferrofluid) have been investigated as a function of the frequency and amplitude of magnetic field by incorporating a complete thermodynamical analysis of the experimental set-up. The heat generation is quantified using the specific power loss (SPL) and compared with the predictions of linear response theory. This analysis sheds light on important physical and magnetic properties of the nanoparticles. [Preview Abstract] |
Thursday, March 6, 2014 1:51PM - 2:03PM |
T7.00014: Physical Vapor Deposition for the Controlled Synthesis of Magnetic Nanocrystals Jonathan Lee, Tony van Buuren, Jason Jeffries, Christine Orme, Scott McCall The ability to tailor the nanoscale architecture of magnetic materials provides an important pathway to enhancing their properties. For multicomponent systems, this necessitates precise control over the structure and composition of the nanoscale materials used in their manufacture. We report on the fabrication of a variety of nanoscale hard and soft magnetic materials using physical vapor deposition and will discuss characterization of their structure and physical properties, conducted with the aim of deriving structure-function relationships. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 [Preview Abstract] |
Thursday, March 6, 2014 2:03PM - 2:15PM |
T7.00015: Magnetic properties of core-shell CoFe$_{2}$O$_{4}$@CoFe-FeO nanoparticles at a high H/T regime F.L.A. Machado, J.M. Soares, O.L.A. Concei\c{c}\~ao, E.S. Choi, L. Balicas The magnetic properties of nanopowders of CoFe$_{2}$O$_{4}$ and of core-shell CoFe$_{2}$O$_{4}$@CoFe-FeO with 6 nm average particle sizes were investigated in the temperature ($T$) range 5 - 300 K under applied magnetic fields $H$ up to 350 kOe. The coercive fields ${H_{C}}$ determined from hysteresis loops were found to be highly enhanced compared to samples with larger particles sizes. For instance, for the CoFe$_{2}$O$_{4}$ nanoparticles ${H_{C}}$ was found to be about 22 kOe for $T$ = 5 K. The broad range of applied fields allowed us to establish of the regime of validity for the law of approach (LA) to saturation which, in turn, allowed the determination of the $T$-dependence for the saturation magnetization ${M_S}$ and for the uniaxial anisotropy constant ${K_1}$. The core-shell exchange-coupling was found to nearly double the values of ${M_S}$ (= 400 emu/cm$^{3}$) when compared to the value for the pure CoFe$_{2}$O$_{4}$ particles (= 240 emu/cm$^{3}$). Moreover, the $T$-dependence of ${K_1}$ for the core-shell particles presented a maximum close to 100 K with substantially enhanced values. The results will be discussed in terms of a particle model which takes into account a thin amorphous layer and the core-shell structure. Work supported by CNPq and FACEPE. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700