Nonmagnetic Alloys Research Articles

HTS SQUID magnetometer with SQUID vector reference for operation in unshielded environment

Using a HTS rf SQUID vector reference, we demonstrated magnetically unshielded operation of an HTS rf SQUID magnetometer. The reference consists of three magnetometer SQUIDS oriented in x, y and z directions. The sensing SQUID magnetometer is z-oriented and positioned at (baseline) distance of 8 cm from the z-reference. A balance (common mode rejection) better than 4000 was achieved by electronic adjustment of the subtraction coefficients of the reference rf SQUID channels in the homogeneous field of large Helmholtz coils. With 3.5 mm diameter washer rf SQUIDs, the magnetic field sensitivity of the magnetometer was 220 fT//spl radic/Hz at frequencies greater than 100 Hz in unshielded environment. A frequent task in nondestructive evaluation of materials is the determination of the magnitude and size of ferrous inclusions in non-magnetic metal alloys. As a preliminary test, we used the magnetometer for the detection of ferrous particles in unshielded environment. A magnetized 10 mg particle was identified from a distance of 80 mm by a scan of its remanent field. Magnetocardiograms (MCG) measurements are also performed.

Large-scale molecular-dynamics simulations of martensitic nucleation and shape-memory effects in transition metal alloys

We discuss results of ab initio and molecular-dynamics simulations of structural phase transformations in magnetic transition metal alloys. In the simulations we make use of the embedded-atom method which allows to take into account the elastic behavior as well as phonon frequencies and vacancy-formation energy of the alloy under consideration. Also this method allows to simulate a large number of atoms required for the simulation of non-equilibrium phase transformations. Structural transformations are possible to simulate either by using the Parrinello scheme for a fluctuating volume box containing the atoms, or by using open boundary conditions. It is shown that structural transformations in the magnetic systems are different from corresponding transitions in the non-magnetic alloys. The simulations describe the large supercooling and superheating effect associated with the structural transformation as a function of the temperature and concentration as well as its dependence on lattice defects. In addition we show that also shape-memory effects can be simulated.

Magnetic nature of (100) surfaces of bcc RuV, RhV, and PdV binary alloys

Based on ab initio calculations we predict that the (100) surfaces of the RuV, RhV, and PdV binary alloys in the bcc structure are magnetic over a broad concentration range although they are nonmagnetic in the bulk and the metals V, Ru, Rh, and Pd are nonmagnetic in the bulk and at the surface. We find that the magnetic moment is basically located at the V site in the surface plane of the alloys and the V moment can be as large as about $1{\ensuremath{\mu}}_{B}$ for an alloy with 75% V concentration. The origin of the surface magnetism is traced back to a surface state of V(100), which becomes occupied due to alloying. Additional nonmagnetic alloys with magnetic surfaces are suggested.

A Method for Laser Zone Texturing of Glass Based Magnetic Media Using Nd:Yag Lasers

AbstractLaser zone texturing of nickel-plated, aluminum based magnetic media has become a preferred method of providing a precisely controlled head landing zone. The Nd:YAG lasers used for this process are not suitable for directly texturing glass substrates. A novel method has been developed which allows the use of the existing Nd:YAG laser systems to zone texture glass based magnetic media.An amorphous sputtered film of a non-magnetic Ni alloy provides a texturing layer which absorbs the laser pulse and controllably forms regular, small protrusions. Optimization of the alloy composition results in small cone-shaped bumps. Laser power sensitivity exhibits a region of invariance for a range of film thickness. This behavior provides a wide margin for manufacture by reducing the effect of thickness variation on laser bump height.Disks fabricated using this form of laser zone texture exhibit excellent tribology performance. TEM images show the Ni alloy to be amorphous and featureless. The sputtered film does not influence the properties of the subsequently sputter deposited isotropic magnetic films.

Incommensurate magnetic structures in transition-metal alloys

Pd-M and Pt-M (M: 3d-element) disordered alloys with M concentration of about 10 at% were studied by neutron scattering. Satellite diffuse peaks were observed on the [1 0 0] axis around the 1 0 0 reciprocal lattice point for all the specimens. These satellite reflections are classified into three groups with different type of magnetism; (1) the concentration wave for non-magnetic alloys (PtV, PdV, PtCr), (2) the spin-density wave for spin-glass alloys (PdMn, PtMn, PdCr) and (3) the transverse wave modulation for ferromagnetic alloys (PdFe, PtFe, PdCo). The satellite peak positions depend on the solute element and solute concentration. These oscillatory waves are interpreted as a screening effect in charges or spin polarizations to the impurity potentials in the host metals with special-shaped Fermi surfaces.

Non-Fermi-liquid, magnetic, and Kondo behavior in the heavy-fermion systemU2Cu17−xAlx(5<~x<~10)

Results of specific heat, magnetic susceptibility, magnetization, and electrical resistivity for the heavy-fermion alloy system U{sub 2}Cu{sub 17{minus}x}Al{sub x} (5{le}x{le}10) are presented. The nonmagnetic alloy U{sub 2}Cu{sub 12}Al{sub 5} exhibits non-Fermi-liquid characteristics at low temperatures: {rho}{proportional_to}T and C/T {proportional_to} lnT. These non-Fermi-liquid characteristics also persist for other alloys corresponding to x{gt}5, which are all weakly magnetic. This magnetic behavior is revealed by a maximum in zero-field-cooled {chi}, a discrepancy between zero-field-cooled and field-cooled {chi} below this maximum, and a corresponding shoulder in C/T. The transition temperature identified by the shoulder in C/T is largest for x=8 (about 2.5 K) and decreases monotonically for either increasing or decreasing x. {copyright} {ital 1997} {ital The American Physical Society}

Theoretical MXD-Investigations on Transition Metal Alloys Containing 4d-Elements

Results are presented on theoretical investigations on the magnetic X-ray dichroism (MXD) of disordered transition metal alloys containing 4d-elements. As found before from neutron scattering studies the induced moments of normally non-magnetic alloy components turned out to vary strongly from element to element and to depend on the magnetic alloy partner. This is reflected in the corresponding magnetic X-ray dichroism spectra that are in general found to be in very satisfying agreement with recent experimental results. In contrast to the interpretation of experimental spectra no fundamental difference could be found concerning the MXD at the L 2,3 -, M 2,3 - and N 2,3 -edges of 4d-elements.

Magnetically stabilized surface alloys

We investigate the interrelation of magnetism and stability of ultrathin magnetic films and come to the conclusion that under certain circumstances there should exist magnetically stabilized two-dimensional surface alloys. We present ab initio results for the formation energy and the interdiffusion energy of Cu(001)c(2 × 2)3d surface alloy films. Results based on the density functional theory in the local spin density approximation (LSDA) indicate the existence of a thermodynamically stable surface alloy: Cu(001)c(2 × 2) Mn. Although in detail, the results depend on the Cu substrate, the trends presented below have an universal character. Therefore, Cu(100)c(2 × 2) Mn is only an example of a much wider class of magnetic surface alloys. Recently, several of these surface alloys have been found experimentally, showing an unexpectingly large structural corrugation of the surface alloy atoms. This will be discussed as a result of a large magneto-volume effect. We found in addition a non-magnetic surface alloy Ti/Cu(001), which is not yet confirmed experimentally. Total energy calculations were carried out using the full-potential linearized augmented planewave (FLAPW) method in film geometry.

Metal-Insulator Transition and Giant Negative Magnetoresistance in Amorphous Magnetic Rare Earth Silicon Alloys.

Large negative magnetoresistance and anomalous magnetic properties are found in amorphous Si doped with magnetic rare earth ions near the metal-insulator transition. The resistivity below 50 K rises orders of magnitude above that of comparable composition nonmagnetic alloys and is strongly reduced by a magnetic field. Magnetization measurements show noninteracting moments at high temperature which develop antiferromagnetic interactions below 50 K. We suggest that these results are due to formation below 50 K of a dense concentration of magnetic polarons which localize conduction electrons.

Comparative assessment of the noise and vibration of centrifugal and induction pumps

case [21. Increasing requirements to lower the vibration and noise of production equipment dictate use of precision methods during fabrication; this significantly increases its cost. Conversion from the centrifugal to the induction scheme [3], which is an asynchronous electric motor with a liquid impeller enables us to eliminate the discrete components of pump vibrations. Such a pump (see Fig. 1) consists of stator 1 made of standard sheets; three-phase winding 2 is situated in the stator slots. Impeller 3 is built of slotless disks pressed onto shaft 4. The fluid flows along helical channel 5, and to protect it from the stator packet and impeller, the latter are enclosed with plastic or nonmagnetic high-resistance steel casings. The helical partition between individual spirals of the channel between inlet and outlet is made of a nonmagnetic low-resistance alloy. The fluid in the channel is placed in motion by pondermotive forces that develop due to interaction between the magnetic field of the stator and the eddy currents induced by the field. The pump is reversible; reversal is accomplished by reversing the ends of the winding. In the vibration spectrum of a pump fabricated in accordance with the scheme under consideration there are no discrete frequencies caused by rotor imbalance, nor blade frequencies of the impeller. Such harmonics as rotor and combination harmonics caused by a different number of stator and rotor slots are also absent. Only stator slot harmonics are retained; yes, and these may be significantly attenuated by use of a packet with closed slots. To lower nonslot harmonics of the motor, it is better to use sine windings [4], the most adaptable to production of which are shortened windings [5], although they are more sensitive to circuit asymmetry than the full windings. The magnetomotive force (MMF) of the full sine windings of each phase contain only basic and slot harmonics:

The JILA Penning trap mass spectrometer

A Penning-ion trap mass spectrometer which is designed to make sub ppb mass measurements on ions is described. The spectrometer incorporates an external ion source for the injection of ions to be "weighed" into the trap. Novel features include a nonmagnetic alloy from which the trap electrodes are machined, as well as an ion detection system based on a superconducting inductor and a very low-noise amplifier incorporating a gallium-arsenide field-effect transistor (GaAs FET). Also discussed is a technique to increase the axial resistive damping constant for trapped ions using a regenerative detection circuit.

CEMS and DCEMS investigations of Al-implanted iron

α-Fe surfaces were implanted with a nominal dose of 5×1017 Al ions/cm2 at 50 keV and a current density of about 3.7 μA/cm2. Samples of different shapes and thicknesses have been used in order to test the influence of heat flow from specimen to target holder during implantation. Integral and energy differential (“depth-selective”)57Fe conversion electron Mossbauer spectroscopy (CEMS and DCEMS) were employed. The spectra indicated a magnetic phase characterised by a broad hyperfine field distributionP(Bhf), a non-magnetic phase, and α-Fe. The relative intensity of the non-magnetic phase was enhanced if the thermal contact during implantation became worse. An energy dependence of DCEM spectra in the L-electron range was observed. Model calculations using L-electron weight functions and experimental concentration profiles obtained by secondary neutral mass spectroscopy (SNMS) yielded fair agreement between calculated and experimental phase signals. The results demonstrate that the non-magnetic Fe-Al alloy phase with high Al concentration is located closer to the surface than the magnetic alloy phase, which extends to much larger depth than expected.

Method of bonding metal carbides in non-magnetic alloy matrix

Method of bonding metal carbides in non-magnetic alloy matrix

Theory of the exchange coupling in magnetic metallic multilayers.

Existing theories of the oscillatory exchange coupling in magnetic metallic multilayers are reconciled within a common approach. It is shown that Ruderman-Kittel-Kasuya-Yosida--type theories and full-confinement quantum-well results are obtained as limiting cases. Numerically useful and model-independent closed-form expressions for the exchange coupling across a nonmagnetic spacer are obtained in terms of the one-electron propagators. The theory can be extended to deal with nonmagnetic alloy spacers and it is argued that the existence of disorder in the spacer may lead to significant reduction of the interlayer coupling.

Composition and catalytic properties of products from the reduction of NiMoO 4

Reduction of α-NiMoO 4 by hydrogen was studied in the temperature range 350–700°C using X-ray diffraction, temperature-programmed reduction and magnetisation measurements. Water vapour was found to have a strong influence on the composition of the reduction products. In the presence of water, pure ferromagnetic nickel and crystalline MoO 2 were found to be reaction products, whereas without water the products were non-magnetic Ni-Mo alloy and poorly crystalline MoO 2. A reduction mechanism is proposed, including initial formation of nickel and MoO 2, followed by their interaction due to spillover of hydrogen. The effect of water was found to be kinetic in nature. Hydrogen temperature-programmed desorption (TPD) spectra of reduction products were studied vs. reduction temperature and time. Maxima on TPD curves at 125,340 and 450° C were tentatively assigned to various three-fold adsorption sites on the surface of Ni-Mo alloy. Catalytic activity in toluene hydrogenation and hydrogenolysis was investigated. Ni-Mo alloying was found to suppress both catalytic reactions, but especially the hydrogenation activity. Trends of activity in both reactions were related to low-temperature features of the TPD spectra. Results of catalytic tests were explained using the ensemble model: only nickel atoms participate in hydrogenation ensembles (Ni 3), whereas hydrogenolysis can proceed on Ni-Mo mixed species.

CRUCIBLE P/M 625

Abstract P/M 625 is a nonmagnetic alloy with outstanding strength and toughness from cryogenic temperatures to 2000 F. It has excellent fatigue strength and stress-corrosion-cracking resistance to chloride ions. This datasheet provides information on composition, microstructureand elasticity as well as fracture toughness. It also includes information on low and high temperature performance, and corrosion resistance. Filing Code: Ni-441. Producer or source: Crucible Compaction Metals.

Transfer hyperfine interaction in Cd1-xMnxTe studied by NMR.

NMR measurements of $^{125}\mathrm{Te}$ and $^{113}\mathrm{Cd}$ have been performed on a series of samples of ${\mathrm{Cd}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Mn}}_{\mathit{x}}$Te (x=0.01, 0.015, 0.02, 0.029, 0.055). The nuclear spin-lattice relaxation rates of the two nuclei are enhanced by two orders of magnitude compared to the relaxation rates of the same nuclei in the nonmagnetic II-VI semiconductor alloys. Well-resolved $^{113}\mathrm{Cd}$ and $^{125}\mathrm{Te}$ spectra were obtained using the magic-angle-spinning technique. The line shifts are temperature dependent and follow the Curie-Weiss law, indicating that the predominant interaction responsible for the NMR behavior is the transfer hyperfine interaction of the ${\mathrm{Mn}}^{2+}$ ion with the Cd or Te nuclei. All the lines in the Te spectra and all but two of the lines in the Cd spectra are shifted to higher frequencies with reference to the NMR line in CdTe. A full spectral assignment has been obtained based on two assumptions: (i) the Mn ions are randomly distributed in the lattice, and (ii) the transfer hyperfine interaction that causes the line shifts depends on the number of bonds between the Mn ion and the Cd (or Te) ion. According to the spectral assignment, the spin density transferred to the Cd sites in the lattice decreases tenfold from one Cd shell to the next.

CRONIX 80 EXTRA, CRONIX 70 EXTRA

Abstract CRONIX 80 EXTRA and CRONIX 70 EXTRA are non-magnetic austenitic alloys for resistance heating elements. This datasheet provides information on composition, physical properties, elasticity, and tensile properties. Filing Code: Ni-408. Producer or source: VDM Technologies Corporation.

Production of amorphous copper-tantalum powders by mechanical alloying: G. Veltl et al, (Fraunhofer Institut, Bremen, Germany), Metall, Vol 45, No 11, 1991, 1131–1133, (In German)

The literature in the period 1972–1978 on the electrodeposition of ternary alloys from aqueous media and their practical applications is critically reviewed with special reference to the type of alloy and the bath characteristics. The alloys are discussed under two broad headings: magnetic alloys and non-magnetic alloys. The latter are further categorized as (a) those containing a third metal with (i) Ni-Co, (ii) Ni-Fe, (iii) Ni-Cu, (iv) Ni-Sn, (v) Fe-Co and (vi) Sn-Co and (b) miscellaneous. It is shown that a wide range of alloy compositions may be obtained from the main baths investigated. The corrosion resistance, hardness, microhardness and structure of the alloys are examined. The role of addition agents in the various baths is discussed in relation to the composition and quality of the deposit. Magnetic properties and the effect of the cathode material on them and on current efficiency and polarization are discussed. Ternary thin films obtained from these baths could be of great industrial value, especially for the computer and electronics industry, and could be used as decorative and protective coatings.

Miniature diamond anvil cell: Incorporating a new design for anvil alignment

A miniature diamond anvil cell (DAC) of overall dimensions φ10×24 mm made of nonmagnetic NiCrAl alloy is described. A new design permits the alignment of anvil flats as perfectly as in traditional DACs. A lever-arm assembly and a fiber-optical system for the cell are described. Two example of experimental results obtained with the cell are given, namely the pressure dependence of the refractive index of diamond and the pressure-induced shifts in the photoluminescence peaks of a quantum well sample. A maximum pressure of 110 GPa was reached with beveled anvils.