We present numerical evidence from atomistic calculations that the coercivity of high-performance NdFeB-sintered-magnets (<20% of the theoretical Stoner–Wolfarth-limit) can be explained by a distorted region of Nd2Fe14B at grain boundaries, which has a reduced local magnetic anisotropy. We show that depending on the boundary composition of fcc-NdO and hcp-Nd2O3, the thickness of this region of reduced anisotropy varies between 0.4 for fcc and 1.6 nm for the hcp phase. For NdO, the distortions are mostly confined in the fcc-NdO-phase but equally distributes in both the hcp-Nd2O3 and Nd2Fe14B. The experimentally measured coercivity of 1.25 T can be understood when taking this distortion and magnetostatic effects into account.

Fabrication and magnetic properties of patterned NiFeMo films electrodeposited in self-assembled nanosphere templates J. Appl. Phys. 109, 054313 (2011); 10.1063/1.3561362 Reduced saturation magnetization in cobalt antidot thin films prepared by polyethylene oxide-assisted selfassembly of polystyrene nanospheres Appl. Phys. Lett. 96, 122504 (2010); 10.1063/1.3371692Oscillatory thickness dependence of the coercive field in three-dimensional anti-dot arrays from self-assembly Using self assembly from lyotropic liquid crystalline phases and from colloidal suspensions of polystyrene spheres templates, we have prepared well-ordered, nanostructured magnetic materials. We present the results of electrochemical deposition of magnetic metals and alloys in the interstitial space between these templates. This technique has enabled us to create magnetic nanostructures with three-dimensional achitectures on length scales of 4 nm-1 m. We find changes in coercive field, by more than 1 order of magnitude, dominated by the effects of the nanoscale shapes. Varying the parameters in the preparation allows us to produce materials with predetermined magnetic parameters. The templated electrodeposition technique offers the potential of a low-cost preparation method for submicron patterned magnetic media.

The propagation of magnetic wave packets in magnetic nanowires was calculated as a function of wire width, field strength, field ramp time, field area size, and geometry of a magnetic nanowire. Spin waves are excited locally by applying a small perturbation in the magnetization in a 20nm wide region. A wave packet is emitted from the input region and travels along the wire with a velocity of 740m∕s. The finite element micromagnetic simulations show that wave packets can be guided along a bent nanostructure without losses due to geometry; amplitude and frequency are exactly the same as in a straight wire with equal distance between excitation point and probe. The wave amplitude was found to decrease with increasing rise time of the excitation field with an upper limit of 100ps. For a Permalloy wire with a thickness of 10nm, the frequency peak changes from 10GHz in a wire with 60nm width to 6GHz in a wire with 140nm width.

The magnetic switching behavior of Co/Pd multilayer-capped nanospheres is investigated by x-ray spectroholography. Images of the magnetic state of individual nanocaps are recorded as a function of externally applied magnetic field and the angle under which the field is applied, pertaining to magnetic data storage applications with patterned, tilted, and perpendicular storage media. Dispersed nanospheres with different coverage in the submonolayer regime are investigated simultaneously in a multiplexed experiment. In clustered nanosphere arrangements, we find that individual switching events are influenced by dipolar magnetostatic interactions. Micromagnetic simulations of the switching behavior complement the experimental observations, corroborating the influence of thermal activation processes and magnetostatic interactions in this system. Such magnetostatic interactions could lead to undesired cross-talk between bits in ultrahigh-density magnetic recording applications.

Recent developments in magnetic applications, such as data-storage, sensors and transducers, are stimulating intense research into magnetism on sub-micrometer length scales. Emerging self-assembly fabrication techniques have been proposed as viable, low cost methods to prepare such sub-micron structures. In this Letter we present studies on magnetic nano-structures with 3D architectures, fabricated using a selfassembly template method. We find that the patterning transverse to the film plane, which is a unique feature of this method, governs the magnetic behavior. In particular, the coercive field, a key parameter for magnetic materials, was found to demonstrate an oscillatory dependence on film thickness.