The role of Ti and Si additions in the magnetic hardening of rapidly quenched Zr2Co11-based nanomaterials has been investigated. Nanocrystalline Zr17–xTixCo83 and Zr18Co82–ySiy are mainly composed of rhombohedral Zr2Co11 and a small amount of orthorhombic Zr2Co11, hcp Co, and cubic Zr6Co23. Ti addition decreases the mean grain size of the magnetic phases, and thus increases coercivity and energ...

High-coercive (Nd,Dy)-Fe-B magnets were fabricated via dysprosium coating on Nd-Fe-B powder. The sputtering coating process of Nd–Fe–B powder yielded samples with densities greater than 98%. (Nd,Dy)2Fe14B phases may have effectively penetrated into the boundaries between neighboring Nd2Fe14B grains during the sputtering coating process, thereby forming a (Nd,Dy)2Fe14B phase at the grain boundar...

G-equations are well-known front propagation models in combustion and are Hamilton–Jacobi type equations with convex but non-coercive Hamiltonians. Viscous G-equations arise from numerical discretization or modeling dissipative mechanisms. Although viscosity helps to overcome non-coercivity, we prove homogenization of an inviscid G-equation based on approximate correctors and attainability of c...

The magnetic behavior of Fe lines on top of a continuous FeF 2 antiferromagnetic layer was investigated as a function of the orientation of the lines with respect to the applied magnetic field and a unidirectional anisotropy established by field cooling. The orientational dependence of the asymmetric loop shift, called exchange bias, shows that the competition between shape and unidirectional a...

Mn–Zn ferrite powders (Mn0.5Zn0.5Fe2O4) were prepared by the nitrate–citrate auto-combustion method and subsequently annealed in air or argon. The effects of heat treatment temperature on crystalline phases formation, microstructure and magnetic properties of Mn–Zn ferrite were investigated by X-ray diffraction, thermogravimetric and differential thermal analysis, scanning electron microscopy a...

An effort has been made to improve the coercivity of nanocomposite Nd10Fe82C6B2 alloys, using small amounts (up to 1 at%) of Cr, Ti, Nb, Zr, and Ga. X-ray studies revealed that the amount of –Fe phase in both as-spun and annealed ribbons was significantly reduced for Nb and Zr substitutions, but increased for all the other substitutions. From the magnetic properties point of view, Zr (1 at%) wa...

We have developed new techniques to measure the magnetization and the coercivity of a uniaxial magnetic material using a torque magnetometer. The magnetization could be measured from the linear dependence at the low-field regime in a plot of the torque versus the applied magnetic field, where the direction of the applied field was perpendicular to the uniaxial orientation. The coercivity could ...

Second order sufficient optimality conditions for bang-bang control problems in a very general form have been obtained in [15, 21, 13, 12, 1]. These conditions require the positive definiteness (coercivity) of an associated quadratic form on the finite-dimensional critical cone. In the present paper, we investigate similar conditions for optimal control problems with a control variable having t...

The magnetic properties of hematite powders produced by a solid state nucleation-and-growth process are studied as a function of temperature T and applied field H. Independently of the temperature, there exists a soft magnetic contribution that is assigned to the canting of spins at the superficial shell of each particle and is not affected by the Morin transition. At 220 < T < TM a magnetic co...

Electro deposition of NiFeWS thin films was carried out from diammonium citrate bath at a constant current density (1 A/dm 2 ) and controlled pH of 8 by varying the citrate bath concentration(0.2, 0.3, 0.4, 0.5 mol / lit). Physical properties such as surface morphology, microstructure and magnetic properties such as coercivity, saturation magnetization and magnetic flux density were investigate...