Khalid Bouziane

Since amorphous Co100−xZrx alloys present ultrasoft properties, higher sensitivity is expected in CoZr/Cu multilayers compared to the Co/Cu system as investigated in the present work from two types (I and II) of hybrid magnetic structures [(F1/F2/F1)Cu]15 where (F1/F2/F1) is a magnetic sandwich corresponding to either [(CoZr/Co/CoZr)]15 (type I) or [(Co/CoZr/Co)Cu]15 (type II) and F1 is a very thin magnetic layer

The static magnetization experimental behavior of cobalt (Co), Permalloy (Py), and nickel (Ni) nanocylinders is obtained from vibrating sample magnetometry while the dynamic behavior for the Co and Py ones is analyzed by means of Brillouin light scattering spectroscopy. Assuming the presence at remanence of two populations of cylinders with up and down magnetizations and including the dipolar coupling between the cylinders, a single analytical model based on a mean-field approach allowed us to satisfactorily analyze both series of experimental results. The model requires three physical parameters, allowing us to derive the in-plane saturation field, the eigenfrequency in the absence of applied field, and the eigenfrequency at the in-plane saturation field; these parameters enable us to adjust the whole variation of the eigenfrequency versus the applied field. Moreover, the effect of the magnetocrystalline anisotropy on the softening of the frequency in the nonsaturated state is clearly evidenced: it is more pronounced when the magnetocrystalline anisotropy is not vanishing and adds to the shape anisotropy (Co c-axis parallel to the cylinder axis); the softening being weak in the other cases (Co c-axis perpendicular to the cylinder axis or Permalloy).

An experimental procedure to measure the interdiffusion coefficient of nondilute binary Ga0.6Pb0.4 liquid alloys exhibiting a miscibility gap is demonstrated. The phase separation is found to be instantaneous, while the formation of a homogeneous alloy is relatively slow. This technique is based on the measurement of the electrical resistivity of liquid alloys during the formation process in a finite capillary.

A high sensitivity of giant magnetoresistance (GMR) has been observed recently from soft magnetic layers such as NiFe, NiFeCo, and FeCoB.12 Amorphous CoZr alloys present ultrasoft properties compared to NiFe.3 GMR has been investigated for amorphous CoZr/Cu/Co thin films grown by rf diode sputtering using a target consisting of a Co disk partially covered with a Zr foil. The influence

... McGaskill and March 1919. McCaskill, JS and March, NH. 1982. Phys. Chem. Liq. , 12: 1 [Taylor & Francis Online], [Web of Science ®] View all references initiated a relation lΔq≈1 relating the finite MFP, l, and a Fermi surface (FS) inflation–deflation (ID) of width Δq. ...

We have performed ab initio calculations based on t-matrix formalism in the framework of the nearly free electron [NFE] theory to determine the electrical resistivity ρ and the thermoelectric power S of three liquid alkali metals, namely, Na, K and Rb. The present approach is primarily based on the Dreirach model that considers a shift EB between the bottom of the free electrons density-of-states (DOS) and the muffin tin zero (VMTZ). Concurrently the second model initiated by Esposito et al. that takes into account the nearly free electrons (NFE) without any gap between NFE-DOS and VMTZ has also been tested. The results ρ and S obtained from the Esposito et al. model are not consistent with experimental counterparts. A substantial improvement of ρ and S values is obtained from Dreirach model provided the temperature dependence of ρ versus energy is considered in order to reproduce the correct sign for S. This observation is presumably related to the fact that in the range between 0 and EF on the energy scale, the DOS for these metals fairly resemble those of free electrons yielding their effective valence Nc to be very close to the valence number Z but with a shift of the bottom of the band which cannot be neglected.

... Mag. 9 (1964), p. 451. [24] Osman Ese and JA Reissland, J. Phys. F: Metal Phys. 3 (1973), p. 2066. [25] M Bestandji, A Makradi, H Chaaba, A Ben Moussa and JG Gasser, J. Phys.: Condens. Matter 2 (1999) p. 8793. [26] W. Jank and J. Hafner, J. Phys. Condens. ...

The electronic and magnetic structures of Fe–V alloys are calculated using the discrete-variational and full-potential linearized-augmented-plane wave methods. The derived hyperfine properties at Fe sites are studied against the number of Fe atoms in the neighbouring shells. As expected the magnetic hyperfine field depends strongly on the number of Fe atoms in the first and second shells of neighbours while its dependence on the variation of atoms in the third shell is weak. The calculated distribution of the magnetic hyperfine fields at the Fe sites, are compared to the experimental data of Krause et al. (Phys Rev B 61:6196–6204, 2000). The contact charge densities and the magnetic moments are also calculated. It was found that the contact charge density increases with increasing V contents and this leads to negative isomer shift on addition of V.

The ferrites Mg0.9Mn0.1Crx Fe2−x O4 ( $0 \leqslant {\text{x}} \leqslant 0.9$ ) were prepared using the conventional double sintering method. The XRD showed that the samples maintain a single spinel cubic phase. The Mössbauer measurements were carried out at room and liquid nitrogen temperatures. From the area ratios of the A and B sites, it was found that the Fe cation population of the A and B sites decreases in proportion to Cr concentration. The contact hyperfine fields at the A and B sites were found to decrease with increasing Cr contents. This was found to be in approximate agreement with the results of magnetization measurement. The distributions of Mg and Mn cations versus Cr concentration were also determined using the Mössbauer and magnetization results. The Curie temperatures were determined and found to agree with the reported values. As the Cr contents increases the relative magnetization, was found to increase at low temperatures and decreases at higher temperatures.

The discrete variational method is used to study the effect of interactions of iron impurities on the magnetic moments, hyperfine fields and isomer shifts at iron sites in silver. We study small clusters of iron atoms as they grow to form FCC phase that is coherent with the silver lattice. The effects of the lattice relaxation and the ferromagnetic and antiferromagnetic couplings are also considered. When Fe atoms congregate around a central Fe atom in an FCC arrangement under ferromagnetic coupling, the local magnetic moment and the contact charge density at the central atom hardly change as the cluster builds up, whereas the hyperfine field increases asymptotically as the number of Fe nearest neighbors increases. Introduction of antiferromagnetic coupling has minor effect on the local magnetic moments and isomer shifts, however it produces large reduction in the hyperfine field. The lattice relaxation of the surrounding Fe atoms towards a BCC phase around a central Fe atom leads to reduction in the magnetic moment accompanied by increase in the magnetic hyperfine field.

The milling of spinel-related Ti-doped Li0.5Fe2.5O4 for different times is studied with XRD, Mössbauer spectroscopy and magnetic measurements. Milling converts the material to Li–Ti-doped α-Fe2O3 nanocrystalline particles via an intermediate γ-LiFeO2-related phase. The role played by the dopant Ti-ion in the process is emphasized.

Nanoparticle iron (Fe)-doped anatase TiO2 was prepared at a low temperature (100°C) and at room pressure. The product was obtained from a boiling solution of an amorphous TiO2 gel mixed with an iron nitrate solution and stirred for 5 h. An amorphous TiO2 gel was obtained from TiCl3 solution and NH4OH as a precipitating agent stirred at room temperature for 1 day. EDAX results on different selected areas of as-prepared Fe-doped anatase TiO2 revealed a homogeneous composition of 17 at.% Fe. Fe–TiO2 has a superparamagnetic state with a possibility of antiferromagnetism at low temperatures. Fe seems to substitute titanium ions without any evidence of other impurities such as Fe nanoclusters or Fe-based oxides.

Nanorods of Fe–TiO2 were synthesized at 100 °C and room pressure by mixing titanium oxide wet gel TiO2·xH2O with a boiling solution of iron nitrate. The results of EDAX, performed on different selected area of the sample, revealed a homogeneous composition of about 3 at% Fe. Electron diffraction and XRD measurements show that the as-prepared Fe–TiO2 and annealed one at 550 °C have both a single rutile structure with no indication about the presence of a secondary phase. The transmission electron microscopy (TEM) micrographs show that both as-prepared Fe–TiO2 and annealed one at 550 °C have nanorod-shape with dimensions length by diameter of about 60 × 5 nm and 52 × 12 nm, respectively. Magnetization measurements show that both samples present a nonzero remanence and a coercivity of 108 and 120 Oe, respectively. At higher temperature, 850 °C, Fe–TiO2 decomposes to rutile TiO2 and new iron–titanate phase.