Metal Gd Research Articles

Rare-earth-containing planar magnetic materials formed using Langmuir–Blodgett technique

We describe the preparation and characterization of rare-earth-containing stearic acid Langmuir–Blodgett (LB) films. Stearic acid monolayer behavior on the rare-earth-containing aqueous subphase has been analyzed by thermodynamic measurements. The monolayer compression isotherm shape changed substantially by varying the anion type at the constant rare-earth cation content and pH in aqueous subphase. The conditions necessary to form highly integrated mono- and multilayered rare-earth-containing LB films were investigated. The deposited mono- and multilayer gadolinium (Gd)-containing LB films were studied by scanning tunneling microscopy (STM) and electron paramagnetic resonance (EPR) techniques. The temperature dependence of EPR signal in Gd-containing LB films indicates the magnetic ordering with a characteristic temperature of transition to complete disordered paramagnetic state of about 500 K, significantly higher than Curie temperature in bulk metal Gd. Low-field hysteresis of microwave absorption was observed in these films and pointed out to the existence of remanence magnetism in created material.

Electronic structure investigations of the Gd(Al1-xMx)2 Laves phase system with M = V, Ti

Although the 3d metals V and Ti do not form binary intermetallic compounds, with the 4f metal Gd, corresponding pseudobinary systems of type Gd(Al1-xMx)2 may exist in the single-phase regime and be prepared by arc melting under pure argon atmosphere up to concentrations of at least x = 0.1. We report results of susceptibility and resistivity measurements for such samples. The Curie temperature and the spin-disorder resistivity are observed to depend sensitively on x. An interpretation is given on the basis of ab-initio electronic structure calculations, using the spin-polarized linearized muffin-tin orbitals (LMTO) method.

The magnetic entropy change properties of La1−zRz(Fe1−x−yCoxAly)13 compounds

The structures, magnetic properties, and magnetic-entropy-changes of La1−zRz(Fe1−x−yCoxAly)13 (R=Ce, Pr, Nd, Sm, Gd, and Dy) were studied. It was found that the crystal structures of La(Fe0.73−xCoxAl0.27)13 maintain the LaCo13-type cubic structure. The relationship between saturation magnetic moments per 3d atom and the number of 3d electrons in the compounds of La(Fe0.73−xCoxAl0.27)13 system can be explained by the rigid-band model at Co-rich side and disagrees with the model at Fe-rich side. When 0.02≤x≤1.0, the compounds have a nearby room temperature Curie temperature, a high saturation magnetization and a high magnetic-entropy-change. When x=0.02 and the external magnetic field is 1.11 MA/m, the maximum magnetic-entropy-change of the La(Fe0.71Co0.02Al0.27)13 compound is 13 kJ/m3⋅K which is about half of that of metal Gd at the same external magnetic field. The saturation magnetization of the compound increases and the maximum magnetic-entropy-change decreases when La is substituted by Ce. The compounds in which La is substituted by other rare-earth elements R (R=Pr, Nd, Sm, Gd, and Dy) decomposed into 1:13-type, 2:17-type, and α-Fe phase. The second rare-earth elements added exist mainly in the 2:17-type phase.

The effects of deposition conditions on microstructure and morphology of r.f.-magnetron sputtered GdTbFeCo thin films

GdTbFeCo alloy thin films were r.f.-magnetron sputtered onto glass substrates and onto carbon-coated 3 mm diameter copper grids for transmission electron microscope observations at different argon pressures P Ar and incident r.f. powers. The mosaic target was assembled by bonding pure metal Gd, Tb and Co chips to a 100 mm diameter pure Fe disc. X-ray and selected area electron diffraction analyses indicate that the deposited GdTbFeCo films are all amorphous and very uniform in both thickness and composition. Transmission electron microscope observations show that as the r.f. power is maintained at 500 W the films deposited at low and moderate pressures ( P Ar ⩽ 1 Pa ) exhibit a smooth and featureless microstructure, while the films deposited at high P Ar (greater than 2 Pa) exhibit a rougher appearance and honeycomb-like network structure surrounded by microvoids. However, the microstructure of films deposited at powers of 200, 500 and 600 W and at a constant P Ar of 2 Pa do not reveal any significant difference except that there is a slight increase in surface roughness with increasing power. These results suggest that the deposition conditions, especially argon pressure, strongly affect the morphology and microstructure and in turn, the stability, magnetic and magneto-optical properties of GdTbFeCo thin films.

Mixed chelates of some trivalent lanthanide ions containing (trans-1,2-cyclhexylenedinitrilo)tetraacetate and norleucinate

Formation constants of mixed chelates with (trans-1,2-cyclohexylenedinitrilo)tetra-acetate (DCTA) as primary ligand and norleucinate (nle) as secondary ligand with metal ions La(III), Ce(III), Pr(III), Sm(III), Gd(III), Tb(III), Dy(III), Er(III), and Yb(III) have been determined by the modified potentiometricpH titration method of Irving-Rossotti in aqueous medium at (295±1) K and fixed ionic strength of μ=0.1M (NaClO4). Formation constants of binary complexes of the metal ions with the secondary ligand have also been determined under identical conditions. The mixed chelates were found to be more stable than the binary ones. The order of stabilities in terms of metal ions is La(III) Gd(III)<Tb(III)<Dy(III)<Er(III)<Yb(III) for binary and ternary complexes with a prominent “Gadolinium break”.

Structure and Magnetic Properties of Sputtered (Gd,Tb)-(Fe,Co) Films

The effect of Ar pressure on internal stress and magnetic characteristics of various rare-earth transition metal (Gd or Tb)-(Co or Fe) films were studied. Increasing the Ar pressure changed the internal stress of all of the films tested from compressive to tensile. The authors suggest that Ar pressure affects internal stress and fractured the cross-sectional structure because the pressure affects the mean free path of the particles.

Photoemission from Magnetic Metals and Alloys

Angle-resolved uv photoelectron spectroscopy has proved to be the most useful probe of the electronic structure in metallic solids. For the investigation of magnetic systems spin-resolved measurments are often preferred. However, considerable detailed information about the electronic structure in certain magnetic metals and alloys can be obtained using conventional and inverse spin-integrated photoemission techniques. In this paper a selection of results from such studies on spin-glass Ag-Mn alloys and on the rate-earth metal Gd are described and compared, where appropriate, with theory.

SHigh resolution 1H nuclear magnetic resonance studies of a flavine and its product with MoCl4

The high resolution 1H nmr spectra of the substituted flavine, 3-N-methyltetraacetylriboflavine (3-Me-TARF), and its non-aqueous solution complexes with Gd(fod)3, Eu(fod)3, MoCl4, and MoCl4•2CH3(CH2)2CN, were studied in order to try to discern the binding sites of the flavine as it attaches to the molybdenum. Evidence was found that all three metal atoms, Gd(III), Eu(III), and Mo(IV), are attached in solution not only by the primary binding (chelating) sites of the flavine, viz., the O-4 and N-5 atoms, but also by an acetyl oxygen atom, at the C-4′ site of the ribityl side chain. 300 MHz spectra of the 3-Me-TARF have permitted the coupling constants for the side chain methine and methylene protons to be obtained.