Dimensionality of a system of exchange-coupled grains and magnetic properties of nanocrystalline and amorphous ferromagnets

Characteristics of random magnetic anisotropy in ferromagnetic films of amorphous Co₉₀P₁₀ and nanocrystalline Ni₇₅C₂₅, Fe₈₀B₄C₁₆, and Co₈₀C²⁰ alloys and also in multilayer films [Co₉₃P₇(x)/Pd(14 Å)]₂₀ and [Co₉₀P₁₀(x)/Pd(14 Å)]₂₀ obtained by various technological procedures were studied experimentally. It was found that the spatial dimensionality (d) of the system of ferromagnetically coupled grains (2R _c ) in the materials under study determined the exponent in the power dependence of the approach of magnetization to saturation in the region of fields H<2A/MR _c ² . The dependence ΔM～H ^?1/2 was observed for nanocrystalline and amorphous films with a three-dimensional grain arrangement. The approach to saturation in multilayer films with a two-dimensional grain arrangement in an individual magnetic layer follows the law ΔM～H ^?1. The main micromagnetic characteristics of random anisotropy, such as the ferromagnetic correlation radius R _f and the average anisotropy 〈K〉 of a ferromagnetic domain with a size of 2R _f , were determined for multilayer Co/Pd films. Correlation was found between the coercive field and these characteristics of random anisotropy.     

Synthesis and characterization of the Pd/InVO4-TiO2 co-doped thin films with visible light photocatalytic activities

Novel Pd/InVO₄-TiO₂ thin films with visible light photocatalytic activity were synthesized from the Pd and InVO₂ co-doped TiO₂ sol via sol-gel method. The photocatalytic activities of Pd/InVO₄-TiO₂ thin films were investigated based on the oxidative decomposition of methyl orange in aqueous solution. The as-prepared samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS) and UV-vis absorption spectroscopy (UV-vis). The results indicate that the Pd/InVO₄-TiO₂ thin films are compact, uniform and consist of sphere nanoparticles with diameters about 80-100 nm. The UV-vis spectra show that the Pd/InVO₄-TiO₂ thin films extend the light absorption spectrum toward the visible region. XPS results reveal that doped Pd exist in the form of metallic palladium. The photocatalytic experiments demonstrate that Pd doping can effectively enhance the photocatalytic activities of InVO₄-TiO₂ thin films in decomposition of aqueous methyl orange under visible light irradiation. It has been confirmed that Pd/InVO₄-TiO₂ thin films could be excited by visible light (E < 3.2 eV) due to the existence of the Pd and InVO₄ doped in the films.     

Auger line shape changes in epitaxial (111)Pd/(111)Cu films

Epitaxial Pd films ranging in thickness from a few tenths of a monolayer up to many monolayers were formed on (111)Cu substrate films at room temperature under UHV conditions. The growth of these Pd films was monitored in situ by Auger electron spectroscopy. The line profiles of the Cu MMM (61 eV) and Pd MVV (329 eV) AES doublets varied significantly with the amount of Pd deposited. A new measure of the AES doublet line profile, called the R-factor, was defined. A graph R_pd versus Pd film thickness shows a sharp decline with increasing thickness. Superimposed on the major trend is a cyclical variation. A corresponding periodicity in R_cu was observed for the Cu MMM (61 eV) AES doublet. The results suggest that the R-factor provides a direct measure of changes in the electronic structures of the overgrowth and substrate films as the former thickens by a layer-growth mechanism.     

Characterization of In/Pd and Pd/In/Pd thin films by ellipsometric, XRD and AES methods

In/Pd and Pd/In/Pd thin films were prepared by thermal evaporation on the SiO₂ substrate in a vacuum. The structural and optical properties of the films were investigated by means of X-ray diffractometry (XRD), Auger electron spectroscopy (AES) and spectroscopic ellipsometry (SE). Auger depth profile studies were performed in order to determine the composition of elements in the Pd-In systems. Interdiffusion of metals was detected at room temperature. Optical properties of Pd-In composite layers formed due to the interdiffusion were derived from ellipsometric quantities Ψ and Δ measured in the photon energy range 0.75-6.50 eV at different angles of incidence. The effective optical spectra show absorption peaks dependent on the composition of nonuniform films. The XRD patterns indicated formation of Pd_1−xIn_x intermetallic phases in the samples.     

[Co/Pd]4–Co–Pd–NiFe spring magnets with highly tunable and uniform magnetization tilt angles

By varying the Pd thickness (t_Pd) from 0 to 8 nm in [Co/Pd]₄/Co/Pd(t_Pd)/NiFe exchange springs, we demonstrate (i) continuous tailoring of the exchange coupling between a [Co/Pd]₄/Co layer with perpendicular anisotropy, and a NiFe layer with an in-plane easy axis, (ii) tuning of the NiFe out-of-plane magnetization angle from 20^○ to 80^○, and (iii) an up to two-fold increase in the NiFe damping. The partial decoupling also results in a highly uniform NiFe magnetization. These properties make [Co/Pd]₄/Co/Pd(t_Pd)/NiFe spring magnets ideal candidates for use as tilted polarizers, by combining stable and well-defined spin directions of its carriers with a high degree of angular freedom.     

Magnetic properties of Co/Pd multilayered films on porous Al<Subscript>2</Subscript>O<Subscript>3</Subscript> templates with developed cell substructure

We studied the structure and magnetic properties of porous multilayered Co/Pd films deposited on the templates of anodized Al₂O₃ with a specific surface morphology that is characterized by a cellular–porous structure with several pores inside each cell. X-ray diffraction analysis and reflectometry are used to study the peculiarities of the formation of phases in deposited films. The effect of morphological features of porous Co/Pd films on their magnetoanisotropic properties and magnetization reversal processes (magnetization reversal mechanisms, domain structure of films, and coercive field H _c ) is revealed by SQUID magnetometry and magnetic force microscopy.     

Spin-wave resonance in Co/Pd magnetic multilayers and NiFe/Cu/NiFe three-layered films

The spectrum of standing spin waves has been detected by the ferromagnetic resonance method in NiFe(740 Å)/Cu/NiFe(740 Å) three-layered film structure in the perpendicular configuration for the copper thickness d _Cu ≤ 30 Å. At thicknesses d _Cu > 30 Å, the resonance absorption curve is a superposition of two spinwave resonance spectra from individual ferromagnetic NiFe layers. For Co/Pd multilayer films, united spinwave responance spectra have also been observed at thicknesses of the paramagnetic palladium layer up to d _Pd < 30 Å. The partial exchange stiffness has been calculated for a spin wave propagating across the Pd layer (A _Pd = 0.1 × 10^?6 erg/cm). This value is always positive (up to the critical thickness of the palladium interlayer d _Pd < d _c) or equal to zero (d _Pd > d _c).     

Optical and electrical properties of nanocrystalline TiO<Subscript>2</Subscript>:Pd semiconducting oxides

Electrical and optical properties of TiO₂:Pd thin films deposited from Ti-Pd mosaic targets sputtered in reactive oxygen plasma have been studied. The properties were investigated for thin films with the Pd amount of 5.5 at. %, 8.4 at. % and 23 at. %. Based on resistivity measurements a drop from 10³ down to almost 10⁻³Ωcm has been recorded when the Pd amount was varied from 5.5 at. % to 23 at. %, respectively. Moreover, it was shown that doping with different amounts of Pd results in the possibility of obtaining both types of electrical conduction: n-type for the TiO₂ with 5.5 at. % and 8.4 at. % of Pd and p-type for the TiO₂ with 23 at. % of Pd thin films. From optical measurements it has been found that as the Pd amount was increased the transmission through the thin films was reduced and position of the fundamental absorption edge was shifted toward a longer wavelength range of up to 600 nm. The optical band gap was calculated for direct and indirect transitions from optical absorption spectra. Structural properties were characterized by X-ray diffraction (XRD) and atomic force microscopy (AFM). The XRD patterns displayed occurrence of the crystalline, TiO₂-rutile for lower Pd amounts (5.5 at. %, 8.4 at. %), while the TiO₂:Pd (23 at. %) thin films displayed XRD-amorphous behaviour. Images obtained from AFM displayed dense, nanocrystalline structure with homogenous distribution of crystallites. Additionally performed secondary ion mass spectroscopy investigation confirmed homogenous distribution of Pd in the whole thickness of the prepared thin films.     

Influence of growth and anneal conditions on the surface roughness of L10 Fe50PdxPt50−x thin films

We deposit Fe₅₀Pd_xPt_50−x alloy thin films by magnetron sputtering onto a TiN seed layer. Chemically ordered L1₀ films are obtained which display large perpendicular magnetic anisotropy. We find that the surface roughness of the film depends strongly on the growth and anneal conditions as well as the Pd composition of the film. Smooth films are obtained by deposition above the chemical ordering temperature and by removing Pd from the alloy.     

Electrical conductivity dependence of thin metallic films of Au and Pd as a top electrode in capacitor applications

Electrical conductivity dependence of thin metallic films of Au and Pd over the different perovskites was investigated. It is found from electrical properties that crystallographic growth orientation of Au and Pd thin layers attained from X-ray diffraction results indicate the slop of current (I)-voltage (V) plots. Besides, surface morphology and topography was considered using Field Emission Scanning Electron Microscopy and Atomic Force Microscopy, respectively. Obtained results showed the Stranski-Krastanov growth of the Pd and Au. Indeed, diminishing of the root-mean-square roughness of Pd/BiMnO₃/SrTiO₃ following by Au deposition should be concerned due to growth of Au onto the crack-like parts of the substrate. These crack-like parts appeared due to parasitic phases of the Bi-Mn-O system mainly Mn₃O₄ (l 0 l) and Mn₃O₄ (0 0 4 l).The different response in the electrical properties of heterostructures suggests that electrical conductance of the Au and Pd thin metallic films have the crystallographic orientation dependence. Furthermore, polycrystallinity of the thin metallic films are desired in electrode applications due to increase the conductivity of the metallic layers.     

Conversion coefficients and E0 transitions in102, 104, 106Pd

In in-beam (p, p′) experiments, electron and γ-spectra were measured in the electron energy range of 500-1840 keV for¹⁰²Pd and¹⁰⁴Pd, and 600–1580 keV for¹⁰⁶Pd. The conversion coefficients of all transitions in this range were obtained with accuracies of about 20%, in some favourable cases 10%. Special attention was given to 0⁺′-0⁺ transitions from the two-phonon triplets to the ground states with the following results for the branching ratios 0⁺′-0⁺ (ground state) to 0⁺′-2⁺ (one-phonon state):¹⁰²Pd:T _k (E0)/T _γ (E2)<(2.1±3.6)·10^{?7 104}Pd:T _k (E0)/T _γ (E2)=(6.0±1.4)·10^{?5 106}Pd:T _k (E0)/T _γ (E2)=(6.0±2.0)·10^?4     

Co/Pd and Co/Pd/CoNi multilayer films: Determination of the sign and magnitude of the exchange interaction of ferromagnetic layers separated by palladium layers

It is found that the exchange interaction of Co (5 nm)ferromagnetic layers via Pd in Co/Pd multilayer films and of Co (5 nm)and CoNi (5 nm) layers via the same nonmagnetic metal in Co/Pd/CoNi films can be both ferro-and antiferromagnetic. The period of the AF-F-AF oscillations is of the order of 0.8 nm, and the amplitude of the oscillations decays as a power-law function ~d _Pd ⁻² . Pis’ma Zh. éksp. Teor. Fiz. 66, No. 7, 487–491 (10 October 1997)     

Influence of layer thickness on the structure and the magnetic properties of Co/Pd epitaxial multilayer films

Co/Pd epitaxial multilayer films were prepared on Pd(111)_fcc underlayers hetero-epitaxially grown on MgO(111)_B1 single-crystal substrates at room temperature by ultra-high vacuum RF magnetron sputtering. In-situ reflection high energy electron diffraction shows that the in-plane lattice spacing of Co on Pd layer gradually decreases with increasing the Co layer thickness, whereas that of Pd on Co layer remains unchanged during the Pd layer formation. The CoPd alloy phase formation is observed around the Co/Pd interface. The atomic mixing is enhanced for thinner Co and Pd layers in multilayer structure. With decreasing the Co and the Pd layer thicknesses and increasing the repetition number of Co/Pd multilayer film, stronger perpendicular magnetic anisotropy is observed. The relationships between the film structure and the magnetic properties are discussed.     

Pairing factor and band structures in odd-A Pd nuclei

The band structures of the odd-A isotopes ¹⁰¹Pd, ¹⁰³Pd and ¹⁰⁵Pd are discussed in the framework of a core plus particle coupling model. The pairing factor (u_j² ? v_j²) contained in the effective coiupling strength is found to be responsible for the change of the $\text{5}\text{2}{}^{\mathrm{+}}\text{ΔJ = 2}$ band structure observed in ¹⁰¹Pd into a $\text{5}\text{2}{}^{\mathrm{+}}\text{ΔJ = 1}$ structure observed in the ^103,105Pd nuclei.     

Projected shell model study of yrast bands in even-even 100–118Pd isotopes

The projected shell model (PSM) study of ^100?C118Pd nuclei is carried out. The reliability of the ground-state wave functions is checked by reproducing yrast spectra and electromagnetic properties. The results of calculations indicate that the observed deformation systematics in ^100?C118Pd isotopes depends on the increase of occupation probability of (1h _{11/2 ??} ) orbit and the deformation producing tendency of n-p interaction operating between Spin Orbit Partner (SOP) orbits (d _5/2)_???(d _3/2) _?? and (g _9/2)_???(g _7/2) _?? . Beside this, the results on band diagrams show that the yrast spectra in Pd isotopes do not arise from a single intrinsic state only but also from multi-quasiparticle states.     

Magnetic circular dichroism of [Co/Pd] and [CoB/Pd] multilayered films

Magnetic circular dichroism (MCD) and X-ray absorption spectra (XAS) at the Co L_2,3-edge of [Co/Pd]₂₀ and [CoB/Pd]₂₀ multilayered films, which were fabricated at 260 °C with different magnetic layer thicknesses (δ), have been measured. The lineshapes of XAS–MCD show that the electronic state of Co 3d of the films hardly changes even when sputtered at higher temperatures. The expectation values of orbital and spin angular momentum (〈L_z〉 and 〈S_z〉) are estimated using the sum rule, and it is found that 〈L_z〉/〈S_z〉 in δ<0.5 nm is larger than that in δ>0.5 nm.     

New Spectroscopic Information on 98Pd

Neutron deficient ⁹⁸Pd nuclei were produced in the ⁵⁰Cr(⁵⁸Ni,2p2α)⁹⁸Pd reaction at a beam energy of 261 MeV. A revision and extension of the level structure of ⁹⁸Pd is proposed. About 40 new transitions have been assigned to, and placed in the level scheme of this nucleus. A sequence of states are candidates for the negative parity 4—quasiparticle states built on the πg _9/2 ^?3 πp _1/2 ^?1 configuration predicted in the framework of the nuclear shell model.     

Gamow-Teller decay of118Pd and of neighbouring even isotopes of palladium

Neutron-rich isotopes of palladium were produced via the fission of²³⁸U by 20 MeV protons. These isotopes were selected using the ion guide-fed on-line mass-separator facility IGISOL at Jyväskylä. Their decays were studied byβ-ray,γ-ray and conversion-electron spectroscopy. For¹¹⁴Pd and¹¹⁶Pd, the decay schemes established previously were confirmed; additionally multipolarities were determined for a few transitions. In the case of¹¹⁸Pd, only an approximate half-life was known from a previous radiochemical experiment. In the present study, 15 gamma transitions were observed, most of which were placed in a decay scheme. The half-life and the decay energy were found to beT _1/2=1.9±0.1 s andQ _β=4.0±0.2 MeV. The decay schemes of¹¹⁴Pd,¹¹⁶Pd and¹¹⁸Pd include — respectively — two, two and four 0⁺→1⁺ Gamow-Teller beta transitions with logft values between 4.1 and 5.1. The strength of these transitions is discussed in terms of the extreme single particle shell model with pairing and the spherical proton-neutron quasiparticle random phase approximation. The possible role of deformation is considered using a shell correction method. Predictions for the decay properties of the as yet unobserved¹²⁰Pd are given.