The reversal mechanisms in arrays of nanometer-scale ~,40 nm diameter! iron particles are studied by low-temperature Hall magnetometry and room-temperature magnetic force microscopy. Rotation of the net array magnetization at low temperatures ~20 K! occurs by both reversible and irreversible modes, the latter revealed by Barkhausen jumps. Spatially resolved measurements at room temperature show...

A potential low magnetic moment standard reference material (SRM) was studied in an interlaboratory comparison. The mean and the standard deviation of the saturation moment m s, the remanent moment m r, and the intrinsic coercivity H c of nine samples were extracted from hysteresis-loop measurements. Samples were measured by thirteen laboratories using inductive-field loopers, vibrating-sample ...

Magnetic properties (coercivity and magnetization) of ferromagnetic films are strongly affected by the proximity to materials that undergo a metal to insulator transition. Here, we show that stress associated with structural changes across the metal-insulator phase transition in VO2 and V2O3 produces a magnetoelastic anisotropy in ferromagnetic films (Co and Ni) deposited on top of the oxides. ...

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...

Abstract. The magnetic properties of magnetite nanoparticles and magnetite-thermoplastic natural rubber (TPNR) nanocomposites was prepared by melt-blending method has been studied using vibrating sample magnetometer (VSM). The saturation magnetization (MS), remanence (MR), squareness (MR/MS), coercivity (HC) and exchange-bias field (Heb) for magnetite nanoparticles and its nanocomposites increa...

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 ...