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Articles 1 - 9 of 9
Full-Text Articles in Engineering
Influence Of Reactive Atmosphere On Properties Of Cobalt Ferrite Thin Films Prepared Using Pulsed-Laser Deposition, A. Raghunathan, David C. Jiles, J. E. Snyder
Influence Of Reactive Atmosphere On Properties Of Cobalt Ferrite Thin Films Prepared Using Pulsed-Laser Deposition, A. Raghunathan, David C. Jiles, J. E. Snyder
David C. Jiles
A series of cobaltferrite (CFO) thin films were grown on SiO2/Si(100) substrates using pulsed-laser deposition (PLD) at substrate temperature (T DEP) of 250 °C and oxygen pressures (P O2) from 0.67 to 6.7 Pa. The influence of PO2 on crystal structure, phase mixture, deposition rate, and magnetic properties was investigated. It is shown in this study that there is a window of PO2 for optimized growth of nanograined CFO films at low T DEP and that either higher or lower values of PO2 produce undesirable multiphase mixtures. CFO filmsgrown at such low substrate temperature and optimized oxygen pressure on thermal …
Effect Of Temperature Variation On The Magnetostrictive Properties Of Coalxfe2−Xo4, Ikenna C. Nlebedim, N. Ranvah, Y. Melikhov, P. I. Williams, J. E. Snyder, A. J. Moses, David C. Jiles
Effect Of Temperature Variation On The Magnetostrictive Properties Of Coalxfe2−Xo4, Ikenna C. Nlebedim, N. Ranvah, Y. Melikhov, P. I. Williams, J. E. Snyder, A. J. Moses, David C. Jiles
David C. Jiles
The effect of temperature variation on the magnetoelasticproperties of the CoAlxFe2−xO4 system (for x=0.0, 0.2, 05, and 0.7) has been studied. Substitution of Al3+ for Fe3+ was found to lower the Curie temperature of the samples and to change the lattice parameter. The magnitude of peak to peak magnetostriction, strain sensitivity, magnetomechanical hysteresis, and relative contributions of λ111 and λ100 to the resultant magnetostriction were found to vary with temperature. The results show the possibility of tailoring the magnetoelasticproperties of highly magnetostrictive cobalt ferrite at temperatures of interest by cation substitution.
Growth Of Crystalline Cobalt Ferrite Thin Films At Lower Temperatures Using Pulsed-Laser Deposition Technique, A. Raghunathan, David C. Jiles, Ikenna C. Nlebedim
Growth Of Crystalline Cobalt Ferrite Thin Films At Lower Temperatures Using Pulsed-Laser Deposition Technique, A. Raghunathan, David C. Jiles, Ikenna C. Nlebedim
David C. Jiles
Cobaltferritethin films were grown on SiO2/Si(100) substrates using pulsed-laser deposition technique at substrate temperatures ranging from 250 to 600 °C. Thermal expansion mismatch between the film and substrate appears to have a substantial effect on the magnetic properties of the cobaltferritefilms, due to the large magnetoelastic coupling of cobaltferrite. It was shown in this study, that polycrystalline films with (111)-preferred orientation could be prepared at substrate temperatures as low as 250 °C. The growth of crystalline cobaltferritefilms at such low temperatures indicates the potential to use cobaltferrite for microelectromechanical systemsdevices and sensor applications including integration with a wider range of …
Resistivity Recovery In Gd5si2.09ge1.91 By Annealing, Ravi L. Hadimani, David C. Jiles
Resistivity Recovery In Gd5si2.09ge1.91 By Annealing, Ravi L. Hadimani, David C. Jiles
David C. Jiles
Irreversible change in resistivity occurs in Gd5(SixGe1−x)4 (with 0.41
Generalized Form Of Anhysteretic Magnetization Function For Jiles–Atherton Theory Of Hysteresis, A. Raghunathan, Y. Melikhov, J. E. Snyder, David C. Jiles
Generalized Form Of Anhysteretic Magnetization Function For Jiles–Atherton Theory Of Hysteresis, A. Raghunathan, Y. Melikhov, J. E. Snyder, David C. Jiles
David C. Jiles
A generalized form of anhysteretic magnetization function to extend Jiles–Atherton theory to different forms of anisotropy has been derived. The general equation for the function has been compared with those of calculations made on the basis of known equations for specific cases: axially anisotropic (one-dimensional), planar anisotropic (two-dimensional), and isotropic (three-dimensional). The Jiles–Atherton model using the proposed functional form of generalized anhysteretic magnetization function for anisotropy dependence has been validated and the necessary equations derived. It has been shown in this work that this functional form of anhysteretic magnetization with necessary boundary conditions can be reduced to the familiar specific …
Field Induced Structural Phase Transition At Temperatures Above The Curie Point In Gd5(Sixge1−X)4, Ravi L. Hadimani, Y. Melikhov, J. E. Snyder, David C. Jiles
Field Induced Structural Phase Transition At Temperatures Above The Curie Point In Gd5(Sixge1−X)4, Ravi L. Hadimani, Y. Melikhov, J. E. Snyder, David C. Jiles
David C. Jiles
Gd5(SixGe1−x)4 exhibits a field induced first order phase transition from a monoclinic paramagnetic to an orthorhombic ferromagnetic at temperatures above its Curie temperature for 0.41≤x≤0.51. The field required to induce the transition increases with temperature. This field induced first order phase transition was observed even above the projected second order phase transitiontemperature of the orthorhombic phase. This may be due to the fact that the applied magnetic field is so high that it causes the broadening to a wider range of higher temperatures of the second order phase transition of the orthorhombic phase, and at such high magnetic fields the …
Temperature Dependence Of Magnetic Anisotropy Of Germanium/Cobalt Cosubstituted Cobalt Ferrite, N. Ranvah, Y. Melikhov, Ikenna C. Nlebedim, David C. Jiles, J. E. Snyder, A. J. Moses, P. I. Williams
Temperature Dependence Of Magnetic Anisotropy Of Germanium/Cobalt Cosubstituted Cobalt Ferrite, N. Ranvah, Y. Melikhov, Ikenna C. Nlebedim, David C. Jiles, J. E. Snyder, A. J. Moses, P. I. Williams
David C. Jiles
The variations in magnetization and magnetic anisotropy of Ge4+/Co2+ cosubstituted cobaltferrite with temperature were investigated for a series of compositions Co1+xGexFe2−2xO4 (0≤x≤0.4). The magnetization at 5 T and low temperature were observed to increase for all Ge/Co cosubstituted samples compared to pure CoFe2O4. Hysteresis loops were measured for each sample over the magnetic field range of −5 T to +5 T for temperatures in the range of 10–400 K. The high field regions of these loops were modeled using Law of Approach to saturation, which represents the rotational and forced magnetization processes. The first order cubic magnetocrystalline anisotropy coefficient K1 …
Estimation Of Second Order Phase Transition Temperature Of The Orthorhombic Phase Of Gd5(Sixge1−X)4 Using Arrott Plots, Ravi L. Hadimani, Y. Melikhov, J. E. Snyder, David C. Jiles
Estimation Of Second Order Phase Transition Temperature Of The Orthorhombic Phase Of Gd5(Sixge1−X)4 Using Arrott Plots, Ravi L. Hadimani, Y. Melikhov, J. E. Snyder, David C. Jiles
David C. Jiles
Gd5(SixGe1−x)4 for 0.41⩽x⩽0.5 is orthorhombic and ferromagnetic at lower temperature, monoclinic and paramagnetic at higher temperature, and shows a first order magnetic-structural phase transition between the two. Magnetic moment versus magnetic field (MH) isotherms were measured just above the first order transitiontemperature for Gd5Si1.95Ge2.05 and Gd5Si2Ge2 samples and the field-induced coupled phase transition from paramagnetic/monoclinic to ferromagnetic/orthorhombic phase was observed. Using the method developed by Arrott [Phys. Rev.108, 1394 (1957)], the ferromagnetic portions of the MH isotherms were used to project the second order magnetic phase transitiontemperature of the orthorhombic phase, a region where the transition does not occur due …
Including Effects Of Microstructure And Anisotropy In Theoretical Models Describing Hysteresis Of Ferromagnetic Materials, H. Hauser, Y. Melikhov, David C. Jiles
Including Effects Of Microstructure And Anisotropy In Theoretical Models Describing Hysteresis Of Ferromagnetic Materials, H. Hauser, Y. Melikhov, David C. Jiles
David C. Jiles
Two recent theoreticalhysteresis models (Jiles-Atherton model and energetic model) are examined with respect to their capability to describe the dependence of the magnetization on magnetic field, microstructure, and anisotropy. It is shown that the classical Rayleigh law for the behavior of magnetization at low fields and the Stoner-Wohlfarth theory of domain magnetization rotation in noninteracting magnetic single domain particles can be considered as limiting cases of a more general theoretical treatment of hysteresis in ferromagnetism.