Element-Specific Magnetic Hysteresis of Individual 18 nm Fe Nanocubes

Abstract

Correlating the electronic structure and magnetic response with the morphology and crystal structure of the same single ferromagnetic nanoparticle has been up to now an unresolved challenge. Here, we present measurements of the element-specific electronic structure and magnetic response as a function of magnetic field amplitude and orientation for chemically synthesized single Fe nanocubes with 18 nm edge length. Magnetic states and interactions of monomers, dimers, and trimers are analyzed by X-ray photoemission electron microscopy for different particle arrangements. The element-specific electronic structure can be probed and correlated with the changes of magnetic properties. This approach opens new possibilities for a deeper understanding of the collective response of magnetic nanohybrids in multifunctional materials and in nanomagnetic colloidal suspensions used in biomedical and engineering technologies.

Direct observation of enhanced magnetism in individual size- and shape-selected 3d transition metal nanoparticles

“…Instead, the available literature reveals a significant scatter of magnetic properties that cannot be assigned only to particle size or environment. For instance, the magnetic anisotropy energies of Fe nanoparticles are reported to range from bulklike to * Corresponding author: armin.kleibert@psi.ch strongly enhanced values in different experiments [13][14][15][16][17][18][19]. Similarly, for Co nanoparticles the experimentally observed values vary over several orders of magnitude [20][21][22][23][24][25].…”

“…However, an unambiguous interpretation of the experimental data is difficult, since most of the reported investigations have been carried out with experimental techniques that average over large distributions of particle sizes, morphologies, and orientations. The situation might be complicated further by the presence of interparticle interactions, which can affect ensemble properties such as magnetization curves acquired with bulk SQUID and vibrating sample magnetometry, or integrated x-ray magnetic circular dichroism (XMCD) spectroscopy [15,34,35].…”

Magnetic imaging with full-field soft X-ray microscopies

“…Examples are magnetic multilayers, where the depthdependence of the magnetization or the spin character at buried interfaces is a very interesting topic to study [43]. Other examples where the 3rd dimension plays an important role are magnetic nanoparticles [44], core-shell structures, such as hard/soft materials for future permanent magnet materials [45], or magnetic supercrystals. The latter ones are arrays of nanocrystals, which self-assemble into superlattices.…”

Size-dependent frequency bands in the ferromagnetic resonance of a Fe-nanocube

“…On the other hand, while their size distribution may well be controllable, the orientation of the magneto-crystallographic directions for two-dimensional arrays of such spherical nanoparticles pose technical difficulties [3]. To circumvent this problem, new wet-chemical methods were invented allowing to fabricate Fe/Fe x O y -core-shell-magnetic nanoparticles in form of cubes with side lengths ranging from 14 nm [4] or 18 nm [5] to over 40 nm [6]. Forming nano cubes arrays deposited onto a substrate sufficiently reduces the parameter space for characterization.…”