7 research outputs found
Magnetic properties of the spinel system MgxMn3-xO4 (0 x 2)
Bol. Soc. Esp. Ceram. Vidrio, 2008, 47, 143-14
An air-cooled Litz wire coil for measuring the high frequency hysteresis loops of magnetic samplesâA useful setup for magnetic hyperthermia applications
International audienceA setup for measuring the high-frequency hysteresis loops of magnetic samples is described. An alternating magnetic field in the range 6â100 kHz with amplitude up to 80 mT is produced by a Litz wire coil. The latter is air-cooled using a forced-air approach so no water flow is required to run the setup. High-frequency hysteresis loops are measured using a system of pick-up coils and numerical integration of signals. Reproducible measurements are obtained in the frequency range of 6â56 kHz. Measurement examples on ferrite cylinders and on iron oxide nanoparticle ferrofluids are shown. Comparison with other measurement methods of the hysteresis loop area (complex susceptibility, quasi-static hysteresis loops, and calorific measurements) is provided and shows the coherency of the results obtained with this setup. This setup is well adapted to the magnetic characterization of colloidal solutions of magnetic nanoparticles for magnetic hyperthermia applications
Structural and magnetic properties of frustrated GaxMn(3-x)O4(1.2 †x †1.6) spinels
International audienceWe report a systematic study of the structural and magnetic properties of frustrated compounds of GaxMn(3âx)O4 (1.2 †x †1.6) prepared by solid-state reaction. Using Rietveld refinement of X-ray diffraction patterns and O'Neill-Navrotsky model, we demonstrate that the system GaxMn(3âx)O4 (1.2 †x †1.6) is an inverse spinel with low inversion parameter, in which Ga3+ replaces Mn3+ cations located in B-sites. The inverse magnetic susceptibility, the shape of ZFC/FC magnetization curves at low temperatures, the existence of hysteresis in all compounds, the frustration parameter and the spontaneous magnetization analysis show that the compounds with x = 1.2â1.4 exhibit a non-collinear ferrimagnetic order and the compounds with x = 1.5â1.6 exhibit a frustrated non-collinear ferrimagnetic order. Spin wave stiffness parameters were determined for each composition using the fitting results of spontaneous magnetization curves. It is demonstrated that for the compounds x = 1.2â1.4 with a non-frustrated ferrimagnetic order, the change of spontaneous magnetization Ms(T) obeys to Bloch's law (T3/2). For x = 1.5â1.6, the compounds exhibit a frustrated ferrimagnetic order, and the Ms(T) shows a deviation from Bloch's law
Complex Nano-objects Displaying Both Magnetic and Catalytic Properties: A Proof of Concept for Magnetically Induced Heterogeneous Catalysis
International audienceAddition of Co2(Co)9 and Ru3(CO)12 on preformed monodisperse iron(0) nanoparticles (Fe(0) NPs) at 150 °C under H2 leads to monodisperse coreâshell Fe@FeCo NPs and to a thin discontinuous Ru(0) layer supported on the initial Fe(0) NPs. The new complex NPs were studied by state-of-the-art transmission electron microscopy techniques as well as X-ray diffraction, Mössbauer spectroscopy, and magnetic measurements. These particles display large heating powers (SAR) when placed in an alternating magnetic field. The combination of magnetic and surface catalytic properties of these novel objects were used to demonstrate a new concept: the possibility of performing FischerâTropsch syntheses by heating the catalytic nanoparticles with an external alternating magnetic field
A Simple Chemical Route toward Monodisperse Iron Carbide Nanoparticles Displaying Tunable Magnetic and Unprecedented Hyperthermia Properties
We report a tunable organometallic synthesis of monodisperse
iron
carbide and core/shell iron/iron carbide nanoparticles displaying
a high magnetization and good air-stability. This process based on
the decomposition of FeÂ(CO)<sub>5</sub> on Fe(0) seeds allows the
control of the amount of carbon diffused and therefore the tuning
of nanoparticles magnetic anisotropy. This results in unprecedented
hyperthermia properties at moderate magnetic fields, in the range
of medical treatments