Elucidating Individual Magnetic Contributions in Bi-Magnetic Fe O /Mn O Core/Shell Nanoparticles by Polarized Powder Neutron Diffraction.

Heterogeneous bi-magnetic nanostructured systems have had a sustained interest during the last decades owing to their unique magnetic properties and the wide range of derived potential applications. However, elucidating the details of their magnetic properties can be rather complex. Here, a comprehensive study of Fe O /Mn O core/shell nanoparticles using polarized neutron powder diffraction, which allows disentangling the magnetic contributions of each of the components, is presented.

'Phantom' atoms and thermal motion in fullerene Crevealed by x-ray and neutron diffraction.

The additional atomic occupancy in the octahedral and the tetrahedral voids of the face-centered cubic lattice (fcc) of fullerene Cwas detected by neutron and x-ray powder diffraction. The observed occupancy exactly tracks the rearrangement of the orientation order with temperature decreases and results from the large atomic vibrations of the carbon atoms constituting the fullerene molecules. This motion assumes a small but finite probability to find the carbon atoms in the fcc interstitial voids, which is modeled by the detected 'phantom' occupancies.

Unravelling the Elusive Antiferromagnetic Order in Wurtzite and Zinc Blende CoO Polymorph Nanoparticles.

Although cubic rock salt-CoO has been extensively studied, the magnetic properties of the main nanoscale CoO polymorphs (hexagonal wurtzite and cubic zinc blende structures) are rather poorly understood. Here, a detailed magnetic and neutron diffraction study on zinc blende and wurtzite CoO nanoparticles is presented. The zinc blende-CoO phase is antiferromagnetic with a 3rd type structure in a face-centered cubic lattice and a Néel temperature of T (zinc-blende) ≈225 K.

Origin of the large dispersion of magnetic properties in nanostructured oxides: Fe(x)O/Fe3O4 nanoparticles as a case study.

The intimate relationship between stoichiometry and physicochemical properties in transition-metal oxides makes them appealing as tunable materials. These features become exacerbated when dealing with nanostructures. However, due to the complexity of nanoscale materials, establishing a distinct relationship between structure-morphology and functionalities is often complicated.

Neutron diffraction study of the (BiFeO3)1-x(PbTiO3)x solid solution: nanostructured multiferroic system.

Neutron diffraction studies performed on the solid solution of (BiFeO(3))(1-x)(PbTiO(3))(x) reveal a mixture of two nanoscale phases with different crystal structures: a rhombohedral BiFeO(3)-based phase and a tetragonal PbTiO3-based phase. The ratio of Fe(3)+ and Ti(4)+ ions in the two phases is practically constant; only the proportion of the phases changes. The magnetic moments in the BiFeO(3)-based phase, in contrast to BiFeO(3), deviate from the basal plane.

Robust antiferromagnetic coupling in hard-soft bi-magnetic core/shell nanoparticles.

The growing miniaturization demand of magnetic devices is fuelling the recent interest in bi-magnetic nanoparticles as ultimate small components. One of the main goals has been to reproduce practical magnetic properties observed so far in layered systems. In this context, although useful effects such as exchange bias or spring magnets have been demonstrated in core/shell nanoparticles, other interesting key properties for devices remain elusive.

Controlled 3D-coating of the pores of highly ordered mesoporous antiferromagnetic Co3O4 replicas with ferrimagnetic Fe(x)Co(3-x)O4 nanolayers.

The controlled filling of the pores of highly ordered mesoporous antiferromagnetic Co3O4 replicas with ferrimagnetic FexCo3-xO4 nanolayers is presented as a proof-of-concept toward the integration of nanosized units in highly ordered, heterostructured 3D architectures. Antiferromagnetic (AFM) Co3O4 mesostructures are obtained as negative replicas of KIT-6 silica templates, which are subsequently coated with ferrimagnetic (FiM) FexCo3-xO4 nanolayers. The tuneable magnetic properties, with a large exchange bias and coercivity, arising from the FiM/AFM interface coupling, confirm the microstructure of this novel two-phase core-shell mesoporous material.

Strongly exchange coupled inverse ferrimagnetic soft/hard, Mn(x)Fe(3-x)O4/Fe(x)Mn(3-x)O4, core/shell heterostructured nanoparticles.

Inverted soft/hard, in contrast to conventional hard/soft, bi-magnetic core/shell nanoparticles of Mn(x)Fe(3-x)O(4)/Fe(x)Mn(3-x)O(4) with two different core sizes (7.5 and 11.5 nm) and fixed shell thickness (∼0.

Size-dependent passivation shell and magnetic properties in antiferromagnetic/ferrimagnetic core/shell MnO nanoparticles.

The magnetic properties of bimagnetic core/shell nanoparticles consisting of an antiferromagnetic MnO core and a ferrimagnetic passivation shell have been investigated. It is found that the phase of the passivation shell (gamma-Mn(2)O(3) or Mn(3)O(4)) depends on the size of the nanoparticles. Structural and magnetic characterizations concur that while the smallest nanoparticles have a predominantly gamma-Mn(2)O(3) shell, larger ones have increasing amounts of Mn(3)O(4).

Magnetic proximity effect features in antiferromagnetic/ferrimagnetic core-shell nanoparticles.

A study of "inverted" core-shell, MnO/gamma-Mn(2)O(3), nanoparticles is presented. Crystal and magnetic structures and characteristic sizes have been determined by neutron diffraction for the antiferromagnetic core (MnO) and the ferrimagnetic shell (gamma-Mn(2)O(3)). Remarkably, while the MnO core is found to have a T_{N} not far from its bulk value, the magnetic order of the gamma-Mn(2)O(3) shell is stable far above T_{C}, exhibiting two characteristic temperatures, at T approximately 40 K [T_{C}(gamma-Mn(2)O(3))] and at T approximately 120 K [ approximately T_{N}(MnO)].

Temperature evolution of sodium nitrite structure in a restricted geometry.

The NaNO2 nanocomposite ferroelectric material in porous glass was studied by neutron diffraction. For the first time, the details of the crystal structure including positions and anisotropic thermal parameters were determined for the solid material, embedded in a porous matrix, in ferro- and paraelectric phases. It is demonstrated that in the ferroelectric phase the structure is consistent with bulk data, but above transition temperature the giant growth of amplitudes of thermal vibrations is observed, resulting in the formation of a "premelted state.

Magnetic ordering and phase transition in MnO embedded in a porous glass.

We present the results of a neutron diffraction study of the antiferromagnet MnO embedded in a porous glass. The type of magnetic ordering and the structural distortion are similar to those of the bulk, but the ordered magnetic moment of 3.84(4)muB/ion is strongly reduced and the Néel temperature is enhanced.