Some low temperature properties of PdCr and PtCr alloys: A comparison with PdNi

Values of the low temperature magnetic susceptibility and specific heat of PdCr and PtCr are presented and compared with the data for PdNi. It is concluded that the properties of PdCr and PtCr can be understood in terms of localized spin fluctuations, like in PdNi.     

Magnetic field dependence of the specific heat of heavily phosphorus doped silicon

The specific heat of phosphorus doped silicon was measured at temperatures 0.1 < T < 4.2 K in external magnetic fields 0 ≦ H_ext ≦ 38 kOe. The phosphorus concentration of the samples ranges from 5.3 × 10¹⁷ to 8.9 × 10¹⁸cm^?3. The magnetic field dependence of the specific heat was observed in the just metallic samples as well as the non-metallic ones. The metal—non-metal transition is discussed on the basis of the Anderson localized states with correlations.     

Muon Knight shift in palladium

The Knight shift at positive muons implanted in pure palladium has been measured as a function of temperature from 19.8 to 883 K. The Knight shift variation is strictly proportional to the Pd magnetic susceptibility with ΔK^μ/Δ_x=-(0.43±0.02) mole/emu=-(2.39±0.11)kG/μ_B. A temperature independent term K^μ(x=0)=+45±10 ppm is found. The results are discussed in terms of the electronic structure of H in Pd.     

Perpendicular magnetic anisotropy and thermal stability in Co2FeAl0.5Si0.5/Pt multilayers

Perpendicular magnetic anisotropy (PMA) and thermal stability of Co₂FeAl_0.5Si_0.5 (CFAS)/Pt multilayer structure prepared by dc magnetron sputtering have been studied. It is found that the strength of PMA depends on the thickness of CFAS layer, and the maximum effective thickness of CFAS with PMA is demonstrated to be about 1.5 nm. The interfacial anisotropy energy K _s is estimated to be 0.45 erg/cm², which is larger than those of Co/Pd and Co/Ni multilayers and responsible for the strong PMA of the CFAS/Pt multilayer. The annealing treatments will give rise to the loss of PMA of CFAS/Pt multilayer and has the relatively less influence with large period number N. With the increasing of the period number N, the CFAS/Pt multilayers tend to have wasp-waist-shaped easy-axis hysteresis loops and multidomain structures.     

Magnetic properties of transition metal substituted MnP

The magnetic properties of polycrystalline samples of Mn_1?tT_tP (T = V, Cr, Fe and Co for 0.00 ≦ t ≦ 0.50) are studied by magnetic susceptibility, magnetization and neutron diffraction measurements. The magnetic phase diagrams of the Mn_1?tT_tP phases exhibit paramagnetic, ferromagnetic, helimagnetic and spin glass regions depending on temperature and substitution (T, t). The concentrated spin glass regions observed in Mn_1?tV_tP and Mn_1?tCo_tP (0.30 ≦ t ≦ 0.50) are believed to result from the disorder in the metal sublattice. The variation of the magnetic moment of the ordered Mn_1?tT_tP phases with the substitution (T, t) is discussed.     

Propagation distances of surface electromagnetic waves on Ni,Pd, Pt,and W metal surfaces

The propagation distances, L_x, of surface electromagnetic waves (SEW) on Ni, Pd, Pt, and W were measured using the two-prism coupling technique at wavelengths from 9.3 to 10.6 microm. Metal samples consisted of films, deposited on glass substrates by electron beam deposition, and metal foils. The measured L_x values for the Pd and Pt firms and Pt foil agree to within 20% of the calculated values from the two-media dispersion relation. The measured values of the propagation distance for the Ni film and foil and the W foil agree to within 50% of the calculated L_x. Scanning electron microscope (SEM) photographs and Auger analysis indicate that film imperfections and foil surface roughness contributed to the lower propagation distances observed for Pt and Pd while imperfections, roughness, and oxidation contributed to the disagreement between measured and calculated propagation distance for Ni and W.     

Tunable laser Stark-difference spectra of CD3OH

We present Doppler resolution limited spectra of the P(J) and R(J) multiplets for J ≦ 10 of the 10-μm CO stretch band of ¹²CD₃¹⁶OH using a tunable diode laser. Relative frequencies within the multiplets accurate to ±0.0002–0.0005 cm^?1 are obtained, but no absolute frequencies are given. We are able to assign most of the hindered rotation and K substructure in these multiplets. The assignments are based on analyses of Stark-difference spectra combined with the ground-state microwave data and the intensity variations which are expected theoretically. The ground and excited state A, K = 1 asymmetry splitting parameters are measured to be δ₁″ = (8.5450 ± 0.0080) × 10^?3cm^?1 and δ₁′ = (9.7706 ± 0.0080) × 10^?3cm^?1, respectively. The ground-state value agrees well with the microwave results. A rapid-scan system for recording data and a computer-aided technique for calibrating and plotting the spectra are described.     

Magneto-volume effect in invar-type amorphous Fe—B alloys

Amorphous Fe_100-xB_x(11.5 ≦ x ≦ 22) alloys having the invar characteristics were prepared by a single roller quenching method to investigate the magneto-volume effect. Forced volume magnetostriction, ?ω/?H, increased remarkably with decreasing boron content and the maximum value obtained was about 90 × 10^?10 Oe^?1 at 11.5 at.% boron. The estimated value of the pressure dependence of the Curie temperature, ?T_c/?P, was considerably large, being comparable to those of crystalline FeNi invar alloys. The ?T_c/?P curve plotted as a function of T_c approximately fitted Wohlfarth's expression.     

Processing and characterization of ultra-thin yttria-stabilized zirconia (YSZ) electrolytic films for SOFC

Sub-micron yttria-stabilized zirconia (YSZ) electrolyte layer was prepared by a liquid state deposition method and with an average thickness of 0.5 μm to improve the performance of the anode-supported solid oxide fuel cell (SOFC). The YSZ precursors, containing yttrium and zirconium species and an additive, poly-vinyl-pyrrolidone (PVP), were spin-coated on a Ni/YSZ anode substrate. Several properties, including crystalline phases, microstructures, and current–voltage (I–V) characteristics, were investigated. The thin film of 4 mol% Y₂O₃-doped ZrO₂ (4YSZ) consisted of cubic, tetragonal, and a trace of monoclinic phases, and showed a crack-free layer after sintering at 1300 °C. The anode supported SOFC, which consists of the Ni–YSZ anode, 4YSZ electrolyte, and Pt/Pd cathode, showed power densities of 477 mW/cm² at 600 °C, and 684 mW/cm² at 800 °C. Otherwise, the surface cracks of the other YSZ-coated samples (e.g. 8YSZ) can be repaired by a multi-coating method.     

The nature of three-pion enhancements in the minimal K-matrix model

The square of the magnitude of the inverse Fredholm determinant associated with the minimal K-matrix integral equations describing three-pion to three-pion scattering was calculated as a function of three-pion mass ¢M from threshold to 1900 MeV for the 0 ≦ I ≦ 2, 0 ≦ J ≦ 2 channels of the three-pion system. The input for these equations consisted of the on-shell π-π t-matrices t₀⁰, t₀², t₁¹, and t₀² obtained from phenomenological phase-shift analyses. For the minimal K-matrix model, the only structure in the natural parity states is an enhancement of kinematical origin at 1284 MeV in the ω-channel. Spurious enhancements appear in all the unnatural parity states considered at roughly 1150 MeV corresponding to the ρπ → ρπ Peierls singularity. In the I = 1 unnatural parity channels, broad enhancements at $\text{1450}\text{MeV}\text{≦ ¢M ≦ 1675}\text{MeV}$ occur. These correspond to the ρπ → fπ fit generalized Peierls singularity.     

Temperature dependence of Knight shifts for 12 B in Pt

The Knight shift of a short lived β-emitting nucleus ¹²B (I = 1, T _1/2 = 20 ms) implanted into Pt has been measured as a function of temperature (140?600 K) by means of the β-NMR method. The relation between the Knight shift and the susceptibility for Pt was deduced, which shows the similar tendency to that for the case of ¹²B in Pd.     

New organometallic salts as precursors for the functionalization of carbon nanotubes with metallic nanoparticles

New organometallic salts were synthesized in aqueous solution and were used as precursors for the functionalization of carbon nanotubes (CNT) by metallic nanoparticles. The precursors were obtained by reaction between HAuCl₄, (NH₄)₂PtCl₆, (NH₄)₂PdCl₆, or (NH₄)₃RhCl₆ with cetyltrimethylammonium bromide (CTAB). The as-obtained (CTA) _n Me _x Cl _y salts (with Me?=?Au, Pt, Pd, Rh) were characterized by Fourier-transform infra-red (FTIR) spectroscopy, ¹H nuclear magnetic resonance (NMR) spectroscopy, and thermogravimetric analysis. These precursors were then used to synthesize metallic nanoparticles of Au, Pt, Pd, and Rh over multiwalled carbon nanotubes (MWCNT). Characterization by scanning transmission electron microscopy (STEM) and thermogravimetric analysis under air reveals that the CNT-supported catalysts exhibit high loading and good dispersion of the metallic nanoparticles with small average particle sizes. The present preparation procedure therefore allows obtaining high densities of small metallic nanoparticles at the surface of MWCNT.     

Statistical analysis of the (d,p) and (d,d) reactions on 40Ca

Excitation functions of the ⁴⁰Ca(d, p)⁴¹Ca and ⁴⁰Ca(d, d)⁴⁰Ca reactions have been measured at 45°, 90°, 135° and 170° from E_d = 4.50 to 5.43 MeV in 10 keV steps. Angular distributions of these reactions have been taken at E_d = 4.70, 5.00 and 5.30 MeV from 25° to 170° in 5° steps. Transitions were observed to the excited states for the range 0.0 ≦ E_x ≦ 3.74 MeV in ⁴¹Ca. Rapid fluctuations in the excitation functions and strong variations of the angular distributions with the incident energy were observed, suggesting that the contribution from compound nucleus processes is very large. Various quantities extracted from the experimental data were compared to the predictions of the statistical theories combined with the DWBA theory for the calculation of the direct reaction amplitudes. The results of the present analysis are consistent with the predictions of the standard statistical theories based on the neglect of the channel-channel correlation.     

New compounds in the Mn-X-Bi system where X = Ni, Cu, RhorPd

A new class of magnetic compounds has been discovered in the temary system Mn-X-Bi where X is Ni, Cu, Rh or Pd. The approximate compositions of these compounds are Mn₅Ni₂Bi₄, Mn₃Cu₄Bi₄, Mn₅Rh₂Bi₄, and Mn₅Pd₂Bi₄. The Bravais lattice is face-centered cubic, and the lattice constants are 12.16 Å (X = Ni), 12.18 Å (X = Cu), 12.31 Å (X = Rh) and 12.44 Å (X = Pd). These compounds are probably ferromagnetic and have Curie temperatures in the range -7°C to 183°C. A crystal structure is proposed for these compounds which contains 88 atoms/unit cell.     

Identification of a bivalent flaw in n-GaAs from noise measurements

Magnetic susceptibility measurements of K₂Pt(CN)₄Br_0.3(H₂ O)_2.3 K₂Pt(CN)₄(H₂ O)₃ and K₂Pt(CN)₄Br₂ are reported as well as ESR measurements on the first compound. The results show that any metallic type of contribution to the susceptibility of the first material is at least an order of magnitude smaller than what is expected from simple band theory or from an interrupted strand model. A small anisotropic Curie type of susceptibility is attributed to ‘impurity’ Pt ions which because of crystaline imperfections have their d_xzd_yz doublet as the highest occupied orbitals.     

Magnetic properties of metallic glasses of the type Fe80−x Pd x B20 and Fe80−x Pt x B20

Amorphous alloys of the type Fe_80???xPd_xB₂₀ and type Fe_80???xPt_xB₂₀ for 0?≤?x?≤?50 have been investigated by means of ⁵⁷Fe Mössbauer spectroscopy and magnetisation measurements in temperatures from 4.2 up to 300 K. Curie temperatures and crystallisation temperatures are found by DTMG-DTA method. Mössbauer spectroscopy magnetic field is observed to visible increase for x?=?1 and 1.5% at room temperature for Pd, while a decrease is observed for higher x values. Curie temperature for Pd alloys has a maximum at x?=?4 with T _C?=?753 K, which supports enforcing influence of Pd at low concentrations of Pd for magnetic interactions. We discuss different explanations for these measurements and compare with other findings for high Pd concentrations and alloys with Pt instead of Pd.     

Single crystal preparation and crystalline electric field parameters of ErAl2

For the first time the preparation of single crystals of ErAl₂ and some isostructural compounds is described. From recently reported susceptibility measurements on ErAl₂ single crystals the parameters of the crystalline electric field are calculated to beB ₄=+15·10^?4°K±30% andB ₆=?2.1·10^?6 °K±30%. These parameters are discussed in terms of the point charge model. This model describesB ₄ andB ₆ and the magnetic properties of ErAl₂ in good approximation.     

Field-induced uniaxial anisotropy in partially ordered Ni3Mn at low temperatures

A uniaxial anisotropy is induced in partially ordered MnNi alloys in the composition range near Ni₃Mn, by applying a magnetic field during cooling from room temperature to 77 K. The uniaxial anisotropy constant K_u depends on both the magnitude of the torque measuring field and that of the cooling field. The easy axis direction tends to be between the 〈100〉 and the direction of the cooling field. The value of K_u shows a maximum when the cooling field is applied along 〈100〉, amounting to 2 × 10⁴ crg/cm³. On the other hand, the crystalline anisotropy is not affected by field cooling. When the temperature is raised from 77 K to 300 K, neither K_u nor the rotational hysterisis loss is observed to have any critical temperature, for a torque measuring field of 20 kOe. As atomic ordering proceeds, these effects become smaller and appear to vanish in the perfectly ordered state.     

Diffusion and correlation effects in iron-doped CoO

The diffusion of ⁵⁹Fe and ⁶⁰Co has been measured in pure CoO and dilute iron-doped CoO, (Co_1?cFe_cO, as a function of temperature (1000–1400°C) and oxygen partial pressure P_{o2), (10^?7 ≦ Po2 ≦ 0 21 atm) The enhancement factors for the diffusivities of iron and cobalt are nearly identical, which suggests that the primary cause of the enhancement is the increased concentration of charge-compensating cation vacancies with the addition of iron. The Fe ions dissolved in CoO appear to exist as a mixture of Fe²⁺ and Fe³⁺ ions, the fraction of iron ions in the three-plus state decreases with decreasing Po2 The simultaneous diffusion of ⁵²Fe and ⁵⁹Fe has been measured as a function of (itpo; at 1200°C The correlation factor for Fe impurity diffusion determined from the isotope-effect measurements is about the same as that for self-diffusion in CoO at high (itPo2} (2 × 10^?3 ≦ p_o2 ≦ 0 21 atm), but increases slightly with decreasing p_O2 Both the enhancement-effect and isotope-effect experiments suggest that the nearestneighbor interactions between Fe ions and vacancies is small, and that the dissolved Fe ions do not have strongly bound electron holes.