Papers by Keyword: Coercivity

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Authors: Marcos Flavio de Campos
Abstract: The effect of crystalline imperfections (as for instance, grain size, inclusions and dislocations) on the coercivity of soft magnetic materials is additive. This only can be explained by an Energy Balance Model. By another hand, the angular dependence of the coercivity only can be explained with a Force Balance Model. Thus both models, Energy Balance and Force Balance have to be invoked for the construction of a general model. The effect of dislocations on the coercivity can be treated as short range magnetostrictive effect. The effect of inclusions needs the consideration of the global magnetostatic energy of the system. The dependence of the coercivity with the grain size can also be explained analyzing the magnetostatic energy. The idea of pinning of domain walls by crystalline defects is reformulated, and it is shown that the coercivity increase due to crystalline defects is principally caused by variations of the magnetostatic energy in the system.
Authors: B. Gebel, M. Kubis, U.K. Rößler, K.-H. Müller
Authors: G. Asghar, S. Nasir, M.S. Awan, G.H. Tariq, M. Anis-ur-Rehman
Abstract: Strontium hexa-ferrite nanoparticles were prepared successfully by simple co-precipitation method. The XRD analysis confirmed the formation of single phase MFe12O19 (M=Sr). Parameters such as crystallite size, lattice constant, X-ray density and porosity were calculated from the X-ray diffraction data. The crystallite sizes were in the range 12-26 nm. The temperature dependent dc electrical resistivity measurements showed that the material was highly. Dielectric constant and dielectric loss factor (tanδ) were measured in the frequency range 20Hz-3MHz. The anomalous behavior of dielectric loss revealed a very important behavior of the prepared sample of SrFe12O19 in different frequency regions and that could be used for new applications of this material. The magnetic properties were determined from the hystersis loop obtained from vibrating sample magnetometer (VSM). The Curie temperature was determined by susceptometer. This material is potentially suitable for use as a recording medium in identification cards and credit cards and for the fabrication of permanent magnets.
Authors: Ane Martínez-de-Guereñu, M. Oyarzabal, F. Arizti, Isabel Gutiérrez
Abstract: The recovery and recrystallization kinetics of a cold rolled interstitial free (IF) steel were studied during isothermal annealing. Magnetic methods based on coercive field measurements, hardness tests and metallography were applied so as to follow the kinetics experimentally. The coercive field measurement technique reveals a higher degree of resolution for monitoring recovery than conventional hardness determination and also allows the recrystallization progress to be monitored. The results obtained are compared to those previously determined for a non-stabilized extra low carbon (ELC) steel. The observed differences are discussed in terms of the presence of microalloying elements, Ti and Nb, which slow down recovery and delay recrystallization.
Authors: Marcos Flavio de Campos, Fernanda A. Sampaio da Silva
Abstract: The applicability of micromagnetics for phases with high magnetocrystalline anisotropy as barium ferrite Ba2Fe12O19 and Nd2Fe14B is discussed. The Stoner-Wohlfarth model is very suitable for such phases, and also for PtFe and PtCo. It was discussed how to take into account the total energy of the system for grain size above the single domain particle size. For this situation of large grain size, the net magnetostatic energy of the system cannot be neglected. From energy considerations, it follows that the coercive force should decrease with the inverse of the square root of the grain size.
Authors: T.D. Shen, U. Harms, R.B. Schwarz
Authors: Ying Shan Chen, Wang Jun Feng, Cui Huan Li, Rui Shan Li, Rui Fan, Hua Yang
Abstract: Nanocrystalline nickel ferrite has been successfully synthesized through carbon-adsorb auto combustion method from Ni and Fe nitrate salts. The powders were characterized by X-raydiffraction(XRD) techniques,scanning electron microscopy(SEM),transmission electron microscopy(TEM) and vibrating sample magnetometry(VSM). XRD indicated that the products were spinel NiFe2O4. SEM and TEM indicated that the particles were spherical with particle size in the range 10-80nm. VSM showed that the sample exhibited typical ferromagnetic behavior at room temperature,while the coercivity of the sample was 150.45Oe and the residual magnetization of the sample was 5.1emu/g.The saturation magnetization of the sample(25.3emu/g)was lower than that for the reported bulk particles(55emu/g), and it has the ultrafine nature.
Authors: P.I. Paulin Filho, R.R. Corrêa
Authors: A. V. Chzhan, G.S. Patrin, S. Ya. Kiparisov, V. A. Seredkin
Abstract: Exchange bias and coercivity of the hysteresis loop of a low-coercive layer in magnetic three-layered structure prepared by chemical deposition are studied. It is established that the coercive force in the films obtained nonmonotonically changed with the low-coercive layer thickness. The specificity of magnetization reversal of exchange-biased layers is analyzed.
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