T. Soumura

Temperature variation of the work function of sputter-cleaned nickel surface

Abstract The temperature dependence of the work function (WF) of a polycrystalline Ni is shown, which is deduced from the contact potential difference measured with reference to Au. The surfaces were sputter-cleaned with Ar + and characterized by SIMS. The influence of the surface erosion due to the bombardment is examined. The WF shows the positive temperature gradient all over the 400–800 K region. Ferromagnetism seems to cause an increase in the WF by about 7 meV at room temperature.

Hysteresis of the work function of Co(0001) surface resulting from an allotropic transformation

The influence of the crystallographic phase transformation on the work function was studied on a Co(0001) surface by a precise measurement of the contact potential difference. The characteristic hysteresis of the work function due to the hcp⇄fcc allotropic transformation was found. The work function changes abruptly by about 2 meV with the phase transformation while decreasing monotonically with temperature except in the transformation range. The contributions of the surface dipole barrier and the chemical potential of electrons to the work function are discussed from the point of view of cellular approximation.

Magnetovolume Contribution to the Temperature Variation of the Magneto-Resistivity in Fe–Ni Invar Alloys

Measurements have been made of the magneto-resistivity and the temperature coefficient of the electrical resistivity in the Fe–Ni alloys containing 33∼42 at%Ni over the temperature range between 77 K and the Curie temperature. On the basis of the analysis inclusive of the forced volume magnetostriction, it becomes evident that the magneto-resistivity in the 42 at%Ni alloy is well explained in terms of the spin disorder scattering, while in the 33∼40 at%Ni the magnetovolume effect considerably contributes. This concentration dependence may be understood by assuming an additional contribution to the conduction electron scattering due to local spin disordered states in the alloys below 40 at%Ni as well as the normal spin disorder scattering. Furthermore, the spontaneous volume strain contribution is indicated to be required for understanding of the temperature coefficient of the resistivity.

Copper Filling of Deep Sub-µm Through-Holes by High-Vacuum Planar Magnetron Sputtering Using Argon Gas with Added Nitrogen: Optimum Quantity of Nitrogen in Argon Gas

We investigated the effectiveness of using argon gas with added nitrogen when filling deep sub-µm through-holes with copper by high-vacuum planar magnetron sputtering, and we examined the optimum amount of added nitrogen. This is done by varying the amount of added nitrogen between 0.5, 1.0, 3.0, 10, and 20 at. % in copper filling experiments conducted at a substrate temperature of 280°C and a gas pressure of p=9.0×10-2 Pa with 80-nm-diameter holes having an aspect ratio of 5.6. The results show that the optimal amount of added nitrogen for copper filling is 1.0 at. %, and that the proportion of conformal filling is 1/5. The reasons for this are discussed in terms of the energy relationship between copper atoms adsorbed physically or chemically by nitrogen, sputtered atoms, and recoil atoms or molecules.

A simple ac susceptibility measuring system at low temperatures

An automated ac susceptibility measuring system based on an ac mutual inductance bridge is described. A personal computer and a digital‐analog converter are used to control the amplitude and phase of the compensatory signal which balances the bridge. An analog multiplier and a variable‐resistance photocoupler are used in the amplitude and phase control circuits, respectively. The magnetic moment of a sample for a 1‐μV output voltage is 3.8×10−6 emu/μV. Sufficient sensitivity was confirmed for an application to oxide superconductors.

Magnetic properties of amorphous (Fe1-xMnx)78B22 alloys

Abstract Amorphous (Fe 1- x Mn x ) 78 B 22 ( x ⩽ 0.4) alloys have been prepared by melt quenching technique and their magnetization measurements have been made over the temperature range from 77 to 800 K. The observed ratio of the spin-ware stiffness constant to the Curie temperature 0.15 meV A -1 is nearly independent of Mn concentration, from which the localized electron nature characterizing the nearest neighbor interaction is preferred in the present alloys. On the basis of the Curie temperature and the average magnetic moment, it is emphasized that the antiferromagnetic coupling between Mn atoms, as well as the environmental effect around some Fe or Mn atom begins to play an important role with increasing Mn concentration especially near the critical concentration at which ferromagnetism disappears.

Temperature variation of the work function of sputter cleaned polycrystalline cobalt

Abstract The temperature variation of the work function of polycrystalline cobalt was measured with the Kelvin method in the temperature range including the allotropic phase transformation near 400°C. The contribution of the surface dipole barrier and the chemical potential of electrons are discussed.

Temperature Variation of the Absolute Thermoelectric Power of Gadolinium

The absolute thermoelectric power S of polycrystalline gadolinium has been measured with and without a magnetic field over the temperature ranges from 77 K to 400 K. As an effect of the magnetic field on S , a peak is observed at 220∼230 K, of which the temperature corresponds to an occuring temperature of a spin rotation from the hexagonal c -axis to a cone structure about the c -axis. The temperature variations of S and the magnetic field effect in ferromagnetic regions are analyzed in terms of the Kasuya theory based on the free electron model. At paramagnetic states, on the other hand, S increases with increasing temperature. This temperature variation is calculated taking into account unusual conductive 5 d -6 s bands with a 3 d electron-like high density of states pointed out by Keeton and Loucks.

Structural analysis of amorphous (Fe1-xMnx)78B22 alloys by X-ray diffraction and electrical resistance

The structure of amorphous (Fe1−xMnx) alloys prepared by a single roller technique has been investigated in terms of X-ray diffraction and electrical resistance. The lattice parameter of the crystalline precipitates, which wereα-Fe and b c t (FeMn)3B, was determined under different heat treatments. On heating up to 440° C where a mixture of amorphous and crystalline phases exists and up to 550° C corresponding to the completion of crystallization, the lattice parameter of theα-Fe phase rises to that of pureα-Fe with increasing manganese concentration. In samples annealed at 660° C for 5 h, the opposite behaviour is observed. These results can be explained on the basis of the position of the boron atom occupying theα-Fe lattice, the pressure effect exerted by the environment, and the enhancement of the chemical short-range ordering between manganese and boron atoms with manganese concentration. In the b c t phase, which shows a reduction in lattice parameter with manganese concentration independent of heat treatment, the effect of redistribution of the atoms in the unit cell should be also taken into account.