P. Zaleski

X-ray Absorption near Edge Structure and Extended X-ray Absorption Fine Structure Analysis of Fe(II) Aqueous and Acetone Solutions

X-ray absorption spectroscopy measurements were used to determine the structure of the first coordination shell of Fe(II) ions in aqueous and acetone based solutions. Extended X-ray absorption fine structure analysis coupled with ab initio X-ray absorption near edge structure calculations confirms the octahedral coordination of the iron ion in water based solution. Data collected for acetone rich solutions can be reproduced assuming coexistence of the octahedral Fe(H(2)O)(6)(2+) and tetrahedral [FeCl(4)](2-) complexes. Distortion of the tetrahedral coordination of ion was detected in some of the acetone based solutions.

Determination of the Riemann modulus and sheet resistivity by a six-point generalization of the van der Pauw method

Six point generalization of the van der Pauw method is presented. The method is applicable for two dimensional homogeneous systems with an isolated hole. A single measurement performed on the contacts located arbitrarily on the sample edge allows to determine the specific resistivity and a dimensionless parameter related to the hole, known as the Riemann modulus. The parameter is invariant under conformal mappings of the sample shape. The hole can be regarded as a high resistivity defect. Therefore the method can be applied for experimental determination of the sample inhomogeneity.

Electric and Magnetic Properties of bcc Fe Based Multicomponent Alloys

The electrical and magnetic properties of a bcc Fe 1- x A x , system with the average atom formed by A = (Al, Si, V, Cr) are presented. Compositions were chosen to obtain alloys of simple structure with control parameter ( x ) covering some important Heusler alloys. Systematic changes in the residual resistivity, magnetic moments, and electronic structure with concentration x are observed. The so-called parallel-resistivity formula ρ -1 =ρ ideal -1 +ρ sat -1 was used for quantitative characterization of the concentrated alloys, where ρ ideal denotes a contribution resulting from different mechanisms of scattering and ρ sat represents a shunt resistivity. At small concentrations x , the main contribution comes from structural disorder. It is shown that the density of states at the Fermi level is substantially reduced at larger x in agreement with results of electronic structure calculations.

The influence of magnetic ordering on the transport properties of Cr–Fe–Mn alloys

Abstract In order to understand conditions in which magnetic ordering affects the electric transport properties in magnetically disordered Cr–Fe–Mn alloys, GMR was investigated in two series of samples: Cr 75+ x Fe 16+ x Mn 9− x and Cr 75+ y Fe 16− y Mn 9 . Magnetic structure of these alloys turned out to be very complex. The observed magnetoresistivity is shown to be particularly sensitive to the FM ordering.

Iron Atoms in Cr–Mn Antiferromagnetic Matrix

The results of the Mössbauer effect measurements on bcc Cr rich Cr-Fe-Mn alloys in temperature range 12–296 K in zero- and in applied magnetic fields are reported. Monochromatic, circularly polarized radiation was used for investigation of iron moments alignment. Strong enhancement of internal hyperfine magnetic field induced by the applied magnetic field was detected and explained as due to dynamical effects. At high temperatures alignment of iron moments in antiferromagnetic phase is weakly magnetic field-dependent. At low temperatures the average hyperfine magnetic field is antiparallel to the net magnetization showing that iron moments are partly ordered by the applied field.

Precise Measurement of Inhomogeneity of 2-D System by Six-Point Method

Nondestructive, quantitative determination of inhomogeneity degree of 2-D system by the measurement of electrical properties is presented. Six point contacts have to be located at arbitrary positions on the sample edge. The sheet resistivity and the inhomogeneity parameter are determined simultaneously by the measurement of nine so-called four-probe resistances. The method is global, i.e., the local inhomogeneity will be always detected irrespectively of their location.

The Resistivity and Hall Effect of the Amorphous Co_{x}Ni_{70-x}Fe_{5}Si_{15}B_{10} Ribbons

The influence of structural disorder and magnetism on the resistivity of the amorphous CoxΝi70-x Fe5 Si15 Β 10 ribbons was investigated. The resistivity vs. alloy composition shows parabolic-like behaviour. In the thermal behaviour, resistivities of the samples show apparent magnetic contribution. They also exhibit minima at temperatures which can be correlated with the Curie temperatures. Above Τ > 0.5ΤC resistivity increases linearly with increasing temperature. This effect is seemingly due to electron-phonon scattering. Obviously, the chemical and positional disorder is responsible for the major part of resistivity.