Hydrogenation Properties of the TiZrYNi (5 ≤ x ≤ 10) and the TiYZrNi (5 ≤ z ≤ 15) Mechanically Alloyed Materials.

The amorphous materials of the TiZrNi composition synthesized by mechanical alloying are widely recognized for their ability to store hydrogen with gravimetric densities above 2 wt.%. It is also known that those alloys can form a quasicrystalline state after thermal treatment and their structural and hydrogen sorption properties can be altered by doping with various elements.

Crystal and magnetic structures of RNiIn compounds (R = Tb and Ho).

Crystal and magnetic structures of RNiIn (R = Tb and Ho) have been studied using powder neutron diffraction at low temperatures. The compounds crystallize as orthorhombic crystal structures of the MnAlB type. At low temperatures, the magnetic moments localized solely on the rare earth atoms form antiferromagnetic structures.

Oxygen deficiency in SrFeO: electrochemical control and impact on magnetic properties.

The oxygen-deficient system SrFeO was explored by heating the stoichiometric Fe oxide SrFeO in well-defined oxygen partial pressures which were controlled electrochemically by solid-state electrolyte coulometry. Samples with up to about 0.2 were obtained by this route.

Symmetry analysis of complex magnetic structure in monoclinically distorted ErCuSn.

The magnetic structure in ErCuSn has been determined using high-resolution powder neutron diffraction, supported by symmetry analysis. At low temperatures, ErCuSn assumes a crystal structure of the TmCuSn type (in the monoclinic space group C2/m). The Er atoms occupy two distinct Wyckoff sites: 2c and 4i.

Crystal and magnetic structure of antiferromagnetic MnPtPd.

We have investigated the crystal and magnetic structure of MnPtPd alloy using powder x-ray and neutron diffraction experiments. This compound is believed to belong to the Heusler family having crystal symmetry I4/mmm (TiAl-type). However, in this work we found that the Pd and Pt atoms are disordered and thus MnPtPd crystallizes in the L1 structure having P4/mmm symmetry (CuAu-I type) like MnPt and MnPd binary alloys.

Verwey-type charge ordering transition in an open-shell -electron compound.

The Verwey transition in FeO, a complex structural phase transition concomitant with a jump in electrical conductivity by two orders of magnitude, has been a benchmark for charge ordering (CO) phenomena in mixed-valence transition metal materials. CO is of central importance, because it frequently competes with functional properties such as superconductivity or metallic ferromagnetism. However, the CO state in FeO turned out to be complex, and the mechanism of the Verwey transition remains controversial.

Evidence for Symmetry Reduction in Ti(AlCu)C MAX Phase Solid Solutions.

Ti[AlCu]C MAX phase solid solutions have been synthesized by sintering compacted TiAlC-Cu composites produced by mechanical milling. Using X-ray and neutron diffraction techniques, it is demonstrated that the Cu mixing into the Al site is accompanied by lattice distortion, which leads to symmetry reduction from a hexagonal to a monoclinic structure. Such symmetry reduction likely results from this mixing through deviation of the A-site position from the special (0, 0, /) position within the P6/mmc space group of the original TiAlC structure.

Lattice-site-specific spin dynamics in double perovskite Sr2CoOsO6.

Magnetic properties and spin dynamics have been studied for the structurally ordered double perovskite Sr2CoOsO6. Neutron diffraction, muon-spin relaxation, and ac-susceptibility measurements reveal two antiferromagnetic (AFM) phases on cooling from room temperature down to 2 K. In the first AFM phase, with transition temperature TN1=108  K, cobalt (3d7, S=3/2) and osmium (5d2, S=1) moments fluctuate dynamically, while their average effective moments undergo long-range order.

Lattice instability and competing spin structures in the double perovskite insulator Sr2FeOsO6.

The semiconductor Sr2FeOsO6, depending on temperature, adopts two types of spin structures that differ in the spin sequence of ferrimagnetic iron-osmium layers along the tetragonal c axis. Neutron powder diffraction experiments, 57Fe Mössbauer spectra, and density functional theory calculations suggest that this behavior arises because a lattice instability resulting in alternating iron-osmium distances fine-tunes the balance of competing exchange interactions. Thus, Sr2FeOsO6 is an example of a double perovskite, in which the electronic phases are controlled by the interplay of spin, orbital, and lattice degrees of freedom.