Magnetic materials research has entered a new and exciting period with the advent of ternary rare-earth-iron-boron compounds, ${\mathrm{R}}_{2}$${\mathrm{Fe}}_{14}$B. From fundamental physics perspective ${\mathrm{R}}_{2}$${\mathrm{Fe}}_{14}$B series its isostructural relatives comprise rich, fascinating area for investigation many intrinsic properties, including magnetic structures, magnetocrystalline anisotropy, rare-earth-transition-metal exchange interactions. Intense interest in...

We report the properties of a new class high-performance permanent magnets prepared from Nd-Fe-B and Pr-Fe-B alloys. Magnetic hardening is achieved by rapid solidification. Energy products these isotropic materials can exceed 14 MGOe with intrinsic coercivities ∼15 kOe. X-ray microstructural analyses indicate that alloys exhibiting optimum characteristics are comprised roughly spherical crystallites, strongly suggesting coercivity mechanism single-domain particle type. The crystallites...

Determination of the crystal structure ${\mathrm{Nd}}_{2}$${\mathrm{Fe}}_{14}$B, a new ternary phase, is reported. It has recently been demonstrated that permanent magnets having large coercivities and energy products can be formed from this underscoring its potential technological importance. We relate intrinsic magnetic properties by considering analogies with previously known rare-earth---transition-metal materials.

We have explored the hard magnetic properties of melt-spun Nd-Fe-B alloys. A maximum energy product 14.1 MG Oe has been observed, highest value ever reported for a light rare earth-iron material. X-ray analyses indicate that alloys exhibiting optimum characteristics are comprised roughly spherical crystallites an equilibrium intermetallic phase. The observed grain sizes in or near estimated single-domain range, suggesting coercivity arises principally from formation particles.

We report additional results of our relativistic calculations $4f$ excitation energies in the rare-earth metals: (i) binding computed for atomic configurations used as inputs to band calculations, well ground states; (ii) parameters and level positions calculated via renormalized-atom method, with emphasis on unoccupied levels; (iii) values $U$, Coulomb interaction energy between two electrons at same metallic site; (iv) simple estimates cohesive energies. Comparisons are made experimental...

A systematic investigation of certain electronic properties the rare-earth metals is reported. Calculations are performed within framework renormalized-atom method in which Hartree-Fock free-atom solutions, with configurations appropriate to metal, initially computed; wave functions then renormalized Wigner-Seitz sphere and used construct $l$-dependent Hartree-Fock-Wigner-Seitz crystal potentials. The following results obtained: (i) Recent spectral information together solutions permits us...

The vibrational dynamics of the retinal chromophore all-trans-to-13-cis photoisomerization in bacteriorhodopsin has been studied with mid-infrared absorption spectroscopy at high time resolution (about 200 femtoseconds). After photoexcitation light-adapted bacteriorhodopsin, transient infrared was probed a broad spectral region, including vibrations dominant C-C, C=C, and C=NH stretching mode amplitude. All photoproduct modes, especially those around 1190 reciprocal-centimeters that are...

We report an effort to optimize the room-temperature permanent magnet properties of Ce-Fe-B materials rapidly solidified by melt spinning. Starting alloy compositions in ternary phase diagram were selected systematically. Ribbons spun from them at a quench wheel velocity 35 m/s, corresponding solidification rate high enough yield mostly amorphous or nanocrystalline material. Heat treatment above 450 °C crystallizes Ce2Fe14B, as x-ray diffraction clearly indicates, with concomitant...

We describe calculations of $4f$ electron binding energies for the rare-earth metals. Relativistic Hartree-Fock atomic configurations most closely approximating those metals are initially performed, and crystal potentials constructed by means renormalized-atom method. band iterated to crude self-consistency total obtained. Correlation effects identical in free atoms assumed. Within assumption a completely screened final state, which site having hole is electrically neutral, estimated at...

We have prepared Li-doped multiwall carbon nanotubes and Li- K-intercalated graphite measured their hydrogen storage properties using a thermogravimetric analyzer (TGA). In flowing H2 atmosphere Li-intercalated both exhibit cyclable weight gain between 200 400 °C loss 500 characterized by distinct unusual temperature profile. find, however, that neither nor is required to generate this TGA feature; we observe it even in Li-containing samples Ar without LiOH either or Ar....

We describe detailed analyses of neutron powder diffraction data on Nd2Fe14B at several temperatures and discuss relationships between the crystal structure magnetic properties via comparison with other rare earth-transition metal systems, Nd2Fe17 in particular. Diffraction studies have also been performed optimum energy product melt-spun Nd-Fe-B ribbons. Those results demonstrate that ribbons are comprised particles diameters a few hundred angstroms.

Rietveld analyses of room-temperature neutron diffraction data for seven Nd2(CoxFe1−x)14B alloys (x=0, 0.1, 0.3, 0.5, 0.7, 0.9, 1) are reported. Throughout the entire composition range Nd2Fe14B-type tetragonal crystal structure is maintained, with lattice constants decreasing significantly as Co concentration x increases. We find that j2-type transition-metal sites preferentially occupied by Fe ions in pseudoternary systems, a result which analogous to preferential occupation c we previously...

A density functional theory investigation of the recently identified hydrogen storage reaction $\mathrm{Li}\mathrm{N}{\mathrm{H}}_{2}+\mathrm{Li}\mathrm{H}\ensuremath{\leftrightarrow}{\mathrm{Li}}_{2}\mathrm{N}\mathrm{H}+{\mathrm{H}}_{2}$ is described. The electronic structure and enthalpy formation $\ensuremath{\Delta}H$ each constituent are calculated in both generalized gradient approximation (GGA) local (LDA). Zero point energies finite temperature corrections to derived via calculation...

Rietveld analyses of room-temperature neutron powder diffraction data for seven Nd2(CoxFe1−x)17 alloys (x = 0, 0.1, 0.3, 0.5, 0.7, 0.9, 1) are reported. In the ternary systems we find that c-type transition metal sites preferentially occupied by Fe ions; concomitantly, d and h have Co occupations larger than those predicted stoichiometry, while f deviate only slightly from random occupation. The magnetic moments obtained refinements indicate a low to high spin state on d, f, as is...

We present estimates of various contributions to the free-atom-metal binding-energy shifts, $\ensuremath{\Delta}{E}_{B}$, for $2s$ and $2p$ core levels iron series elements and, comparison, $3{d}_{\frac{5}{2}}$ level Sn. Our results indicate that sharp break in experimental $\ensuremath{\Delta}{E}_{B}$ values occurring between Ni Cu is due variation differences $d$-electron count, i.e., $d$ configuration, atom metal. Ley et al. who neglected $d$-configuration differences, attributed a change...

A systematic investigation of the alkaline earth hydrides $\mathrm{Be}{\mathrm{H}}_{2}$, $\mathrm{Mg}{\mathrm{H}}_{2}$, $\mathrm{Ca}{\mathrm{H}}_{2}$, $\mathrm{Sr}{\mathrm{H}}_{2}$, $\mathrm{Ba}{\mathrm{H}}_{2}$, corresponding deuterides, and their antecedent metals is reported. We calculate lattice parameters, electronic vibrational energies, enthalpies formation at 0 $298\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, components elasticity tensor, ${C}_{ij}$, polycrystalline moduli based on Hill...

We report magnetization measurements of all RFe3 intermetallic compounds known to form (R = Y, Sm, Gd, Tb, Dy, Ho, Er, Tm). A two-sublattice molecular field model is employed analyze the data except in case YFe3, for which one magnetic sublattice assumed. In general, adequately describes temperature dependence magnetization. For SmFe3 our results suggest that samarium and iron moments are ferromagnetically coupled.

We consider the approach to saturation for cubic and uniaxial polycrystalline, single-domain ferromagnets from remanent state. For both {111}- {100}-easy systems we find that coefficient \ensuremath{\beta} in law $M(H)\underset{\stackrel{\ensuremath{\rightarrow}}{H}\ensuremath{\infty}}{\ensuremath{\approx}}M(1\ensuremath{-}\ensuremath{\beta}{K}^{2}{/M}^{2}{H}^{2}),$ where $M$ is magnetization $K$ principal anisotropy constant, departs well-known result $\ensuremath{\beta}=8/105$ obtained an...

Magnetization measurements for the R6Fe23 (R=Y, Dy, Ho, Er, Tm, Lu) intermetallic compounds and molecular field analyses of data are reported. A single-sublattice model accurately describes temperature dependence magnetization Y6Fe23 Lu6Fe23. Excellent correspondence with other is provided by a two-sublattice which allows canting rare earth iron moments. Our results indicate significant departure from antiparallel moment alignment in Tm6Fe23.