Monodisperse face-centred tetragonal (fct) FePt nanoparticles with high magnetic anisotropy and, therefore, high coercivity have been prepared via a new heat treatment route. The as-synthesized face-centred cubic FePt nanoparticles were mixed with salt powders and annealed at 700 ̊C. The salts were then removed from the particles by washing the samples in water. Monodisperse fct FePt particles w...

Error estimates are derived for an augmented Lagrangian approximation to an optimal control problem. Convex control constraints are treated explicitly while a Lagrange multiplier is introduced for the nonlinear system dynamics. The nonlinear optimal control problem does not fit the classical theory for estimating the error in multiplier approximations, since the natural coercivity assumption is...

We report an experimental approach to separate temperature dependent reversible and irreversible contributions to the perpendicular magnetic anisotropy of Fe films grown at low temperatures on Cu(001) substrates. The surface anisotropy K(S)(T) is found to decrease linearly with temperature, causing a thermally induced spin reorientation into the plane. The irreversible shift of the spin reorien...

Using x-ray absorption spectromicroscopy we have imaged the uncompensated spins induced at the surface of antiferromagnetic (AFM) NiO(100) by deposition of ferromagnetic (FM) Co. These spins align parallel to the AFM spins in NiO(100) and align the FM spins in Co. The uncompensated interfacial spins arise from an ultrathin CoNiOx layer that is formed upon Co deposition through reduction of the ...

A version of Zhong’s coercivity result (1997) is established for nonsmooth functionals expressed as a sum Φ +Ψ, where Φ is locally Lipschitz and Ψ is convex, lower semicontinuous, and proper. This is obtained as a consequence of a general result describing the asymptotic behavior of the functions verifying the above structure hypothesis. Our approach relies on a version of Ekeland’s variational...

Hysteresis loops of randomly oriented grains with uniaxial anisotropy were computed on the basis of an array of 27 Wigner Seitz cells representing crystallites which interact by exchange coupling at the grain boundaries. The computed coercivity increases linearly with increasing interatomic exchange. Using the experimental anisotropy and exchange parameters for Sm(FellTi), we found 1.lo&=1.2 T ...

The main goal of this work is to study the structural and magnetic properties of iron nanowires and iron nanoparticles, which have been fabricated in almost the same processes. The only difference in the synthesis is an application of an external magnetic field in order to form the iron nanowires. Both nanomaterials have been examined by means of transmission electron microscopy, energy dispers...

Nanomagnetic structures of hydrothermal NiZn ferrites sintered at various temperatures was studied in this work through Magnetic Force Microscopy (MFM) using different magnetically characterized tips. The magnetic patterns varied according to the tip employed and were correlated to the magnetic induced field generated by these different coated tips. NiZn ferrites were produced at 200°C by hydro...

Electrical field activated sintering technology combined with micro-forming (Micro-FAST), as a new rapid powder sintering/forming method, is used to fabricate FeCo alloy parts. The successfully prepared parts have high saturation of 214.11 emu/g and low coercivity 16 Oe, these values are 20% 10% higher than that commercially available FeCoV on the respectively. During process, current applicati...

We have investigated magnetic properties for reactor pressure vessel model alloys with variable Cu contents, subjected to neutron irradiation up a fluence of 9×1019 n cm−2. Unlike monotonic increase microhardness fluence, the major-loop coercivity decreases at higher and decrease becomes larger alloy containing amount Cu. The measurements first-order reversal curves (FORCs) high-Cu show that po...