Materials Literature
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Materials with a large capacity to dissipate mechanical energy are of interest for passive vibration damping. We have measured the zero-field damping capacity of the giant magnetostrictive terbium–dysprosium–iron compounds by quasistatic stress–strain hysteresis loops. The magnetization and strain of the samples were…
Pulsed laser deposition using bulk NiOFe2O3 targets onto heated substrates has been used to synthesize single phase Ni spinel ferrite films onto various substrates. Flowing oxygen has been used during the deposition to maintain the oxygen stoichiometry. Ni ferrite films have been deposited onto C-, R-, and A-plane sap…
RFe7 compounds with the TbCu7 structure have been synthesized by annealing of mechanically alloyed powders. The lattice constants a and c decrease with increasing atomic number of the rare earths except for Ce which has a different valence state. Introduction of nitrogen interstitial atoms into the structure results i…
Mechanically alloyed magnets SmCox (x=6.0–11.0) have been prepared using starting materials of commercial SmCo5 and Co powders. X-ray diffraction data indicate that the equilibrium Sm2Co17 phase can be achieved in a nanocomposite Sm2Co17/Co system at x=8.5–11.0, while a Sm2Co17/SmCo5 structure occurs at x=6.0–8.0. The…
We present a potential-energy function for H interacting with bulk metallic Ni. The potential is parametrized to be accurate both for H adsorbed on Ni surfaces and for H absorbed at interior sites. The function introduces a nonlocal density dependence into the embedded-atom method formalism. We show that the function…
Self-consistent spin–polarized electronic structure calculations have been carried out to derive the magnetic properties of the Sm2Fe17−xAx (A=Al, Ga, Si and x=0 and 1). The influence of impurities on the Curie temperature (TC) of Sm2Fe17 has been studied using the spin–fluctuation approach of Mohn and Wohlfarth. The…
We have explored the colossal magnetoresistance (CMR) effect in the antiferromagnetic La0.5Ca0.5MnO3 compound. In the absence of a magnetic field (H), the solid is a canted antiferromagnetic (AFM) insulator. An applied H in the Tesla scale induces a first order AFM to FM phase transition, and correspondingly, an insul…
We have applied a multiphonon-assisted energy transfer model, which has been verified for the Yb-doped InP system, to Er-doped GaAs, Nd-doped GaP, and Nd-doped GaAs. By applying this model, the temperature dependence of the decay time of the 4f-shell luminescence can be calculated using two parameters. One parameter i…
In order to understand the magnetic properties of the substituted rare-earth-iron alloys, it is especially important to know the location of the substitutional atoms within the iron lattice. The site distributions of some nontransition-metal substituents in the substituted Nd2Fe17−xTx alloys have previously been repor…
The problem of direct transition intensities in angle-resolved UV photoelectron spectroscopy is addressed. We demonstrate that the angular distribution of intensities integrated over the full $3d$ band of copper is dominated by final-state scattering effects much like those observed in the diffraction of core level ph…
Systematic magnetization and ferromagnetic resonance (FMR) measurements have been performed on thin-film samples of La0.67Ba0.33MnOz (TC∼340 K). It is found from the FMR data that as- grown films show broad lines whose width Γ increases to nearly 1 kOe as T reduced to 77 K. The increase roughly follows the increase in…
Using density-functional methods, we study the electronic structures of the lanthanum-based ‘‘double-exchange’’ perovskite magnets. Antiferromagnetic insulating solutions are obtained for both the end members, LaMnO3 and CaMnO3, within the local density approximation (LDA), with the Jahn-Teller (JT) distortion of the…
This letter addresses the temperature dependence of some of the electrical properties of 0.2-μm-thick SrBi2Ta2O9 capacitors with platinum electrodes on silicon wafers for nonvolatile memory applications. Investigations of the remanent polarization, the nonvolatile polarization and the coercive field with pulse amplitu…
Spring magnets consist of a mixture of exchanged coupled, hard and soft magnetic phases and exhibit improved energy products and remanence. In this study, magnets containing a mixture of Nd2Fe14B and Fe3B have been fabricated using melt spinning under either Ar or He atmospheres. In addition, samples have been heat tr…
Ba-hexaferrite thin films for recording media applications are often fabricated by a two-step process: sputter deposition of an amorphous precursor, followed by annealing to crystallize the BaFe12O19 phase. The magnetic anisotropy of the crystalline films can be either in-plane or perpendicular, depending on the sputt…
Previously, nuclear magnetic resonance experiments and diffusion calculations have indicated that the distribution of nitrogen atoms in a Y2Fe17Nx particle with intermediate N content is characterized by a nitrided region and an unnitrided region. In order to directly detect this two-region configuration, x-ray diffra…
Calculation of the unstrained band offsets between conventional zinc-blende II-VI superlattices (ZnS/ZnSe/ZnTe), or between magnetic II-VI superlattices (MnS/MnSe/MnTe) or combinations thereof ($\frac{\mathrm{Mn}X}{\mathrm{Zn}X}$) show that (i) the range of offsets spanned by different magnetic II-VI superlattices is…
We study the stability range of coherent Ge quantum dots with an epitaxial Si shell. The critical radius is evaluated as a function of Si shell thickness and Ge nanocrystallite radius by comparing the energy of the system in the coherent and incoherent state. We find that the system is coherent up to a Ge nanocrystall…
We report a spin analysis of core-level photoelectrons excited by circularly polarized x rays from a non-magnetic solid. In a combined experimental and theoretical study, we show that the spin-orbit-split W $4{f}_{\frac{7}{2}}$ and $4{f}_{\frac{5}{2}}$ photoemission lines from W(110) exhibit high spin polarizations of…
The magnetic properties of the ferromagnetic compounds, SmFe11Ti and SmFe11TiH1−δ, which are potential candidates for high performance permanent magnets are investigated. At room temperature both compounds exhibit a uniaxial anisotropy, with the easy direction of magnetization parallel to the tetragonal axis. High fie…