Than Duc Hien

Magnetic properties of LaNi5-based compounds

Magnetic properties of the La(Ni4.5M0.5), (La1−xRx)Ni5 (M=Fe, Co, Mn, Cu, Cr, Si and R=Nd, Pr) and their hydride compounds have been studied by magnetization measurement using a VSM. The susceptibility (χ) of the samples increases with Co, Mn, Fe, Nd, Pr but decreases with Cu, Cr, Si additives. The hydrogenation changes magnetic properties of the La(Ni4.5M0.5), (La1−xRx)Ni5 parent compounds. Specially, the milling process changes magnetic properties of LaNi5. This work indicates that besides electrochemical measurements, the study of magnetic properties also gives important information on the quality of rechargeable sealed nickel–metal hydride batteries.

Role of the rare-earth atoms affecting the spin fluctuation scattering in the (RE, Y)Co2 compounds

Abstract For a number of (RE, Y)Co 2 compounds (RE = Er, Dy, Tb, Gd) the influence of the localized 4f moments, interacting with the itinerant 3d matrix, is accentuated by subtracting the resistivity of YCo 2 from the observed resistivity values. The results show that spin fluctuation scattering is enhanced not only just above T c in the compounds where the induction of the itinerant Co moments starts, but in the whole paramagnetic temperature range in all investigated compounds.

The influence of Tantalum content in relation to substrate temperature on magnetic and structural properties of Co-Cr-Ta thin films

In this study, we investigated the influence of Ta content (in Co86Cr12Ta2 and Co82Cr13Ta5 compositions) on magnetic and structural properties of Co–Cr–Ta perpendicular media samples grown on Si substrates at different substrate temperatures during RF-sputter deposition. In general, coercivity of Co82Cr13Ta5 samples is higher than that of Co86Cr12Ta2 samples, whereas the perpendicular c-axis orientation of Co86Cr12Ta2 samples is better. Ta content was suggested to be in between 2 and 5 at% to give optimum magnetic and structural properties.

Magnetic properties of RCu2 (R = Dy, Ho, Er) and DyxY1−xCu2 compounds

Abstract The low field temperature dependence of the magnetization of some RCu 2 (R=Dy, Ho, Er) compounds has been measured under hydrostatic pressures up to 5 kbar. Apart from the antiferromagnetic-paramagnetic transitions additional transitions have been observed for HoCu 2 and ErCu 2 below their Neel temperatures. For the Dy x Y 1− x Cu 2 compounds the dependence of the Neel temperature on the Y content has been determined. The results are discussed in the RKKY model.

Application of the individual site anisotropy (ISA) model to the intermetallics with the ThMn12 structure

Abstract The individual site anisotropy model was applied to the Y(Fe 1− x Co x ) 11 Ti, Y(Fe 1− x Co x ) 10 Mo 2 and YFe 12− x V x compounds with the ThMn 12 structure. Based on the relation between the CaCu 5 and ThMn 12 structures, the results are discussed in comparison with those previously obtained for R(Co 1− x Fe x ) 5 and related compounds.

Effect of Fe substitution for Co in GdCo4B compound

Abstract The effect of Fe substitution for Co at small concentrations (x ≤ 0.1) on magnetic properties of Gd(Co1-xFex)4B compounds has been studied. Upon substitution, the compensation temperature is nearly constant, the Curie temperature changes slightly whereas the magnetic anisotropy is modified significantly. The Fe-concentration dependence of the magnetic anisotropy has been analysed by means of the individual site anisotropy (ISA) model. The magnetic phase diagram of the Gd(Co1-xFex)4 compounds is discussed.

Study of the influence of hole concentration on high-Tc superconductivity of cuprates Bi-2212 by X-ray photoelectron spectroscopy

Abstract In this paper, we report the observation of X-ray photoelectron spectra (XPS), which were obtained from high- T c superconducting compounds Bi-2212 with some percentage of 3d elements (Fe, Co, and Ni) substituted for copper. The changes in characteristics of XPS spectra Sr 3d and Cu 2p 3/2 with the doping content were explained in the relation to the hole concentration on CuO 2 planes, which resulted in high- T c superconductivity.

Studies on AB5 metal hydride alloys with Co additive

Abstract Some effects of Co additive on the magnetic and electrochemical properties of the alloy series La 0.8 Nd 0.2 Ni 4.9− x Co x Si 0.1 ( x =0.1, 0.5, 0.75, 1 and 1.5) have been studied. The results of magnetic measurements indicate that the susceptibility ( χ ) and the Curie-temperature ( T c ) of the samples increases with Co addition. The milling and the charge–discharge process change the magnetic properties of the as-prepared samples. Electrochemical measurements show that small additions of Co improve the performance of metal hydride alloy electrodes as charge transfer facilities.

Spin fluctuation scattering in RCo2 compounds

Abstract Field dependent resistivity measurements have been performed for NdCo 2 and PrCo 2 compounds. The influence of the localized 4f-moments, interacting with the 3d-matrix, is accentuated by subtracting the resistivity of YCo 2 from the observed resistivity values. The excess resistivity Δπ (= π (RCo 2 ) - π (YCo 2 )) which is enhanced above T C by the presence of 4f-atoms is strongly temperature dependent. The results are discussed in terms of the thermal variation of the number of the Co-enhanced paramagnetic atoms.

Spin reorientation in Tb/sub 1-x/Y/sub x/Fe/sub 11/Ti compounds

The Tb/sub 1-x/Y/sub x/Fe/sub 11/Ti (x=0, 0.2, 0.4, 0.6 and 0.8) compounds have been studied in magnetization and AC-susceptibility measurements as a function of temperature. The results show that the Tb/sub 1-x/Y/sub x/Fe/sub 11/Ti compounds with x=0, 0.2 and 0.4 undergo a spin reorientation of the axis-to-plane type (referred to decreasing temperature), while the samples with x=0.6 and 0.8 remain easy-axis compounds down to the lowest temperature measured (4.2 K). The spin-reorientation temperature, T/sub sr/, is found to decrease with increasing Y content. The observed temperature dependence of the magnetic structure of this series of compounds has been analyzed on the basis of a crystal-field model with the following set of crystal-field parameters: B/sub 2//sup 0/=0.45 K, B/sub 4//sup 0/=-1.8/spl times/10/sup -4/ K and B/sub 6//sup 0/=0 K. >