Experimental susceptibility of CuFe, AgFe and MoFe and the results of the Wilson theory

The low temperature susceptibility of the local moment system $\text{Mo}$Fe has been measured by the Mössbauer effect. The susceptibility for this system and for the system $\text{Cu}$Fe, $\text{Ag}$Fe and $\text{Au}$Fe show general agreement with the prediction of the Wilson theory.     

Hall effect in dilute magnetic alloys

We review the theory and the experimental results on the Hall effect in noble metals containing magnetic impurities of transition metals. In order to illustrate the various types of observed effects, we focus succesively on selected systems: $\text{Cu}$Mn, with only enhancement of the ordinary Hall effect due to the existance of different spin-up and spin-down currents; $\text{Au}$Fe and $\text{Au}$Cr, with skew scattering by magnetic impurities; $\text{Cu}$MnT ternary alloys (where T is a non-magnetic impurity), with skew scattering effects due to combined spin—orbit scattering by non-magnetic impurities and spin scattering by Mn impurities. The skew scattering in $\text{Au}$Fe and $\text{Au}$Cr can be ascribed to the orbital character of the impurity moments and accounted for in an orbitally degenerate virtual bound state model. However, the anomalous temperature dependence of the skew scattering in Kondo alloys at low temperature is not well understood. We also present some magnetoresistance data in order to describe the links between the Hall effect and the magnetoresistance in magnetic alloys. In particular, we relate the skew scattering and the magnetoresistance anisotropy observed in $\text{Au}$Cr alloys.     

Atomic short-range order and its relation to the magnetic behavior of noble-metal based spin-glass alloys

We have investigated the spatial distribution of magnetic atoms (Mn or Fe) by determining the short range order parameters for the archetypal spin-glass alloys: $\text{Cu}$Mn, $\text{Au}$Mn, $\text{Au}$Fe and $\text{Pt}$Mn in the dilute limit. All four systems possess atomic short-range order (ASRO) such as to enhance local ferromagnetic regions. In the latter three systems the ASRO is relatively strong and initiates long-range structures which develop with increasing concentration and which eventually destroy the spin-glass state.     

Study of interdiffusion of Ni/Fe layers by Auger Sputter profiling

Bulk and grain boundary diffusion of Fe into Ni films has been studied under UHV in the temperature range of ?150 to 500°C using AES and sputter profiling methods. The concentration profiles at the interface are corrected for the various broadening and damage effects inherent in ion bombardment. Grain boundary diffusion coefficients are derived on the basis of the Whipple model. The measured activation energies are 46 $\text{kcal}\text{mole}$ for bulk diffusion and 34 $\text{kcal}\text{mole}$ for grain boundary diffusion. An additional migration phenomenon not previously resolved is observed for very thin films annealed at relatively low temperatures (150–250°C). A possible mechanism involved in this initial “interface healing” is discussed.     

Investigation on surface compositions of CuNi alloy under Ar+ ion bombardment by ISS and in situ AES measurements

Surface compositions of CuNi(50 wt%) alloy under 3 keV Ar⁺ ion bombardment were measured by Auger electron spectroscopy (AES) and ion scattering spectroscopy (ISS). In situ AES measurement of sputter-deposited layer and sputtered sample surface indicated that surface composition became Ni-rich due to Ar⁺ ion sputtering at steady state, in accord with previous reports of preferential sputtering. ISS measurements with 3 keV Ar⁺ ions, however, have suggested that the composition of the outermost atom layer is not Ni-rich but slightly copperrich. This leads to the conclusion that the degree of preferential sputtering is small and that the question of preferential sputtering, particularly, the ratio of the sputtering yields, $\text{S}{}_{\mathrm{<mtext>Cu</mtext>}}\text{S}{}_{\mathrm{<mtext>Ni</mtext>}}$, based on AES measurement requires further examination.     

Analysis of the residual linewidth in electron-paramagnetic resonance of AuEr and AuYb

For single crystals of $\text{Au}$Er and polycrystalline $\text{Au}$Yb the residual EPR linewidth due to inhomogeneous broadening is analyzed. Angular dependent experiments show uniquely that the main contribution is due to internal strain rather than to dipolar interaction. The independent experiments for $\text{Au}$Er and $\text{Au}$Yb yield a consistent set of parameters but show a dipolar contribution two to three times smaller than calculated. An explanation for this is given. The very precise determination of H_res yields |Δg | = |ρJ₁| < 0.005 for $\text{Au}$Er, a vanishing g-shift.     

SIMS,AES, work function and flash desorption measurements of the CO adsorption on NiCu alloy surfaces

The chemisorption of CO on Cu, Ni and CuNi alloy surfaces was examined by SIMS, work function measurements and desorption spectroscopy. Using a dynamic SIMS technique the M⁺, M⁺₂, MCO⁺ and M₂CO⁺ emission at different temperatures (100–400 K) was measured as a function of CO exposure. In agreement with the work function and desorption experiments an increase of M⁺ and MCO⁺ emission due to the CO adsorption on Cu was found only at low temperatures (100–190 K). On the Ni surface an increase of Ni⁺, NiCO⁺ and Ni₂CO⁺ was measured up to 400 K. The adsorption of CO on CuNi alloy surfaces — as derived from the work function measurements — can be described by the assumption of two different states of adsorbed carbon monoxide. They can be characterized by different binding energies and from sign and magnitude different work function changes. These states were interpreted as adsorption at Ni or Cu sites of the alloy surfaces, respectively. To a certain extent the SIMS results from the alloy surfaces are incompatible with the work function measurements and desorption spectroscopy and the SIMS studies on the pure metals. A Cu⁺ emission with comparable intensity to the Ni⁺ emission was found for alloys with bulk concentrations of 60 and 40 at% Cu at 300 K. The ratio $\text{Ni}{}^{\mathrm{+}}\text{Cu}{}^{\mathrm{+}}$ was nearly independent of CO pressure and temperature. The measured ratios of $\text{Cu}{}^{\mathrm{+}}{}_2\text{(}\text{Cu}{}^{\mathrm{+}}\text{+}\text{Ni}{}^{\mathrm{+}}\text{)}$, $\text{Ni}{}^{\mathrm{+}}{}_2\text{(}\text{Cu}{}^{\mathrm{+}}\text{+}\text{Ni}{}^{\mathrm{+}}\text{)}$ and $\text{CuNi}{}^{\mathrm{+}}\text{(}\text{Cu}{}^{\mathrm{+}}\text{+}\text{Ni}{}^{\mathrm{+}}\text{)}$ with values about 10^?2 can be explained the basis of a statistical arrangement of Cu and Ni atoms in the alloy surface. The intensities of the MCO⁺ emissions are 10² times smaller than the corresponding values of the pure metals. No emission of M₂CO⁺ was found on CuNi during CO adsorption.     

Systematically weak temperature dependence of electric field gradients in distorted cubic metals

The temperature dependence of the electric field gradient for radiation-damaged copper and for the dilute alloy Zn$\text{Ag}$ has been measured using the perturbed angular correlation technique. A systematically weak temperature dependence is found for distorted cubic metals compared to non-cubic metals. The strong temperature dependence for the Zn$\text{Ag}$, In$\text{Ag}$ and Sn$\text{Ag}$ alloys as reported in literature has not been confirmed in the present experiment.     

Magnetoelastic effects in dilute magnetic alloys

Ultrasonic studies of $\text{Cu}$Mn, $\text{Au}$Mn and $\text{Au}$Fe alloys where the concentrations of the transition metal ranges between 1 and 10% show that the longitudinal sound velocity has a marked field dependence at temperatures below the peak in the magnetic susceptibility and a negligible field dependence above it. This suggests that there may be an ordered magnetic state in these alloys.     

Remanent magnetisation properties of the spin glass phase

We have made a systematic survey of the field and temperature dependence ofthe remanent magnetisation of the spin-glass system $\text{Ag}$Mn in the concentration range 1 to 24%. We parametrise this ensemble of data by the linear field dependence of the thermoremanent magnetisation (TRM), the quadratic field dependence of the isothermal remanent magnetisation (IRM), and by the saturation value of the remanent magnetisation in high field. This enables us to search for a universal behaviour of these parameters in reduced units of temperature and field. We show that at various temperatures the ensemble of reduced curves corresponding to a given concentration alloy are not identical. However, we show that this behaviour is the same at all concentrations, i.e. the field dependence of IRM and TRM depend only on T/T_g. We further show that this dependence is not affected by factors such as the time of measurement, the presence or absence of short-range order or the strength of the amisotropy energy in the system. A suitable parametrisation of this temperature dependence, which we take as exponential, allow us to compare different spin glass systems. We show that the same conclusions appear to hold in $\text{Cu}$Mn, $\text{Au}$Fe, $\text{Pt}$Mn and $\text{La}$Al₂Gd from which we obtain almost the same exponential coefficients. These facts strongly suggest that the mechanism responsible for the existence of a remanent magnetisation exclusively involves exchange interactions and is a general property of the spin-glass phase.     

Local moment spin resonance in a Kondo system

The ESR of the system $\text{Yb:}\text{Au}{}_{\mathrm{x}}\text{Ag}{}_{\mathrm{1?x}}$ has been investigated for 0.7 ? x ? 1. The g-shift (Δg) and the temperature derivative of the linewidth $\text{(}\text{ΔH}\text{ΔT}\text{)}$ increase with decreasing Au concentration. For T ? 2°K effects in $\text{(}\text{ΔH}\text{ΔT}\text{)}$ are observed, which are attributed to the Kondo effect.     

Analysis of the high-temperature spin-glass susceptibility: Determination of the local magnetic exchange

New measurements are reported of the magnetic susceptibility above the freezing temperature T_f for noble-metal spin-glasses with $\text{1}\text{2}$ to 6 at.% Fe or Mn. The susceptibility for T_f<T?5 T_f is not Curie-Weiss, but local magnetic correlations manifest themselves and provide a key for the determination of the exchange interactions in spin-glasses. The exchange parameters J_n are resolved up to 5 neighbors for $\text{Au}$Fe, $\text{Cu}$Mn, $\text{Au}$Mn and $\text{Pt}$Mn through a configuration ensemble calculation which includes atomic short range order.     

Mössbauer effect measurements on a AuFe spin glass

Zero field Mössbauer measurements have been carried out between 1.9 and 30 K and at room temperature on a $\text{Au}$-3 at% Fe sample. There is a quite well defined change of regime at about 19.5 K, well above the cusp temperature of this sample which was measured to be 16.4 K. In the temperature region below 19.5 K the spectra can best be described in terms of a static, inhomogeneously broadened field distribution, and at higher temperatures the spectra are compatible with relaxation broadening. Estimated relaxation rates in this regime are similar to those obtained by other techniques.     

Disorder induced core photoelectron linewidth broadening in AgPd alloys

High resolution core level photoelectron spectra for a series of Ag_xPd_1−x alloys have been measured and reveal a large “disorder broadening” effect. A comparison of measurements of this effect for three alloy systems, Ag_xPd_1−x, Cu_xPd_1−x and Cu_xZn_1−x, with results of ab initio calculations is presented. Poor agreement is obtained and possible reasons for this observation are discussed.     

Nuclear spins of 186, 187, 188, 189, 189m Au

The nuclear spins of some neutron deficient gold isotopes have been measured using the atomic-beam magnetic resonance method. The following results have been obtained: ¹⁸⁶Au 10.7 min) I = 3, ${}^{187}\text{Au}\text{(8.5}\text{min}\text{) I =}\text{1}\text{2}$, ${}^{188}\text{Au}\text{(8.8}\text{min}\text{) I =}\text{1}\text{2}$, ${}^{189}\text{Au}\text{(28.3}\text{min}\text{) I =}\text{1}\text{2}$ and ${}^{\mathrm{<mtext>189</mtext><mtext>m</mtext>}}\text{Au}\text{(4.6}\text{min}\text{) I =}\text{11}\text{2}$. The spins of these typical transitional nuclei are discussed briefly in terms of various nuclear models.     

Lattice specific heat of copper based dilute alloys at low temperature

The low-temperature lattice specific heat of copper-based dilute alloys $\text{Cu}$ Sn, $\text{Cu}$ Ga, $\text{Cu}$ Ge, $\text{Cu}$ Zn and $\text{Cu}$ Ni has been studied theoretically on the basis of Green's function theory. A nearest-neighbour impurity model, with certral and non-central force constant changes has been employed. The effect of volume change is taken into account, and is seen to be important. The calculated results are in excellent agreement with experimental measurements, and the derived force constants are seen to be reasonable.     

Skew scattering of electrons in a spin glass

The field and temperature dependences of the extraordinary Hall effect in alloys of the $\text{Au}$Fe system have been measured for the first time over a range that encompasses the spin glass regime. We are able to show how the data reflect the competition between the spin glass ordering interactions and the disruptive effects of temperature and applied magnetic field.     

Surface oxidation kinetics of sputtering targets

Films of compounds can be deposited by sputtering a metal or alloy target in an atmosphere containing a suitable reactive gas. Both Al and 90 : 10 In : Sn targets have been sputtered in argon/oxygen mixtures to obtain Al₂O₃ and indium tin oxide films. The experiments were carried out in a planar magnetron sputtering system with both dc and rf excitation. To investigate the kinetics of the reactive sputtering process, the time dependence of the total gas pressure was measured after a change in oxygen flow rate or sputtering power; a capacitance manometer gave accurate and reproducible results. There were simultaneous changes in the rf matching conditions when rf excitation was used. These changes can be attributed to the formation of an oxide on the target surface. The time dependence of the oxygen pressure measured for the Al and In : Sn targets have been used to compare various models of the reactive sputtering process. Fitting of the experimental values to these models yields values of the equilibrium oxide thickness on the target and these have been compared with measured values. For rf sputtering of an Al target at 500 W with flow rates of $\text{3}\text{ml}\text{min}$ and $\text{2.2}\text{ml}\text{min}$ for argon and oxygen respectively, both the calculated and the measured value of the oxide thickness is 100 nm.     

2S12 state ions in inorganic luminescent materials

Selected examples of impurity ions with one unpaired electron in an unfilled shell are Pb³⁺ ions in II–IV compounds (ZnO, ZnSe, ZnTe), Pb³⁺ in CaWO₄,F centres in alkali halides and Ag⁰ and Au⁰ atoms in radiophotoluminescent (RPL) glasses. Comparative studies of EPR, luminescence, thermoluminescence and related phenomena were performed on systems with ²S_{$\text{1}\text{2}$} state ions as central ions and systematically varying ligand ions in the temperature range from 1.6°K to 450°K. Luminescence bands attributed to internal transitions ²P_{$\text{3}\text{2}$,$\text{1}\text{2}$}→²S_{$\text{1}\text{2}$} ground state are reported especially with respect to the corresponding EPR data. All data are summarized in a molecular orbital model for the luminescence complex.     

Response function of a tunable diode laser spectrometer from an iterative deconvolution procedure

A deconvolution procedure commonly used for resolution enhancement of spectra has been applied to the determination of the response function of a tunable diode laser spectrometer. The method is sufficiently fast and simple for routine application when non-negligible instrumental broadening must be corrected for. Absolute linestrengths of CH₄ in the 1327 cm⁻¹ region and line positions of HNO₃ in the 1335 cm⁻¹ region, measured with the aid of the deconvolution technique, are reported here.