A.Y. Takeuchi

Magnetic properties of perovskite-type Fe–Ni nitrides γ′-(Fe1−xNix)4N(0⩽x⩽0.9)

In this work, we have succeeded in preparing γ′-(Fe1−xNix)4N powder samples for x up to 0.9 and have undertaken a systematic study of their structural and magnetic properties by x-ray diffraction and vibrating sample magnetometry. The lattice parameters of the nitrides decrease monotonically from 0.3795 to 0.3747 nm with increasing Ni concentration. The saturation magnetization, measured at room temperature and liquid nitrogen, was found to decrease with increasing Ni concentration. The Curie temperature TC also decrease with increasing Ni concentration, as well as with decreasing lattice parameter. Our results show that the lattice parameters, σs and TC behave in contrast with those of the corresponding fcc γ-Fe1−xNix alloys, for which each of these properties exhibits a maximum at some intermediate composition.

Changeover in the order of the magnetic phase transition in the intermetallic compounds (Er1−xTbx)Co2

Abstract Electrical resistivity, magnetization and AC susceptibility measurements have been carried out to investigate the order of the magnetic phase transition in (Er 1− x Tb x )Co 2 compounds. In this system a changeover from first- to second-order transition at about x c =0.60 was observed. This result is discussed in the framework of the generalized Inoue-Shimizu phenomenological model. Moreover, a microscope explanation about the order of the phase transition in terms of spin fluctuation and metamagnetism of the Co-3d subsystem is offered.

Magnetic properties of Ce(Fe1−xAlx)2 (Al-RICH)

Magnetic properties of the Laves phase system Ce(Fe1−xAlx)2 were investigated by means of magnetization and electrical resistivity measurements for 0.60 ≤x< 0.90. X-ray powder diffractograms reveal that at least up to 40% of iron in CeAl2 (x = 0.60) the samples are single-phase. A magnetic phase diagram is proposed where, in this range of concentration, the system changes from a ferromagnetic to a quasi-ferrimagnetic phase around x = 0.80. At low temperatures the mixed phase character was indicated by spin-glass behaviour, walls pinning of ferromagnetic domains and frustration.

Electrical resistivity of the pseudo-binary system Ce(Fe1-xAlx)2

Abstract The Laves phase pseudo-binary system Ce(Fe 1- x Al x ) 2 for x ≤0.20 has been studied by means of electrical resistivity measurements from 1.5 to 300 K. It is shown that with Al addition, the long range magnetic order of CeFe 2 is destroyed and that a spin glass phase brings in a minimum in the total resistivity with T min proportional to x . The freezing temperatures T f are always smaller than T min and there appears a negative coefficient of the T 3/2 dependence below T f . The minimum in dϱ/d T is well correlated with T f .

Magnetic behaviour of the intermetallic compound Ce(Fe0.8Al0.2)2

The magnetic properties of the intermetallic compound Ce(Fe0.8Al0.2)2 are studied by means of magnetisation measurements as functions of temperature and field. The low-temperature magnetisation versus temperature curve shows a peak at 12.5K with remanent effects characteristic of spin-glass behaviour. At higher temperatures a second peak was observed at 165K. The nature of this second peak is qualitatively discussed.

Electrical resistivity of CeFe2

Electrical and magnetic properties of CeFe2 were investigated from the temperature dependence of the electrical resistivity in the range 1.5-300K. The critical temperature, determined from the maximum of d rho /dT, gives Tc=220K and the temperature-independent magnetic resistivity is 87 mu Omega cm. This value is compared with the corresponding value in YFe2. At low temperatures the resistivity shows a fairly large term proportional to AT2 up to about 32K with A=1.2*10-2 mu Omega cmK-2.

Spin fluctuation in RCo2 compounds

Abstract Electrical resistivity and magnetization measurements have been used to study the character of the spin fluctuations in the paramagnetic phase of RCo2 (R=Er, Ho, Tb) and Er(Co,Ni)2 compounds. The localized 4f moments present some local effective molecular field above Tc that polarizes the Co atoms leading to an additional increase in the scattering process.

RECOVERY OF ERCO2 FERMI LEVEL BY SUBSTITUTION OF CO BY NI AND FE

Magnetic and electrical resistivity measurements performed in Er(Co1−xNix)2 have shown that the critical concentration for the first-order magnetic phase transition is near to xc=0.10. For higher Ni concentration the results suggest that Co is no longer magnetic. Experimental results presented here for Er(Co0.8Ni0.2xFe0.2(1−x))2 and Er(Co0.9Ni0.1xFe0.1(1−x))2 systems, show that when Co is replaced by Fe, the 3d band is filled up, whereas for Ni substitution that band is depleted. The saturation moment obtained from isothermal magnetization measurements indicates that Co recovers its moment and couples parallel to the Fe moment and antiparallel to the Er moment. Characteristics of spin fluctuation are also observed. These results show that with a suitable combination of Co, Ni, and Fe we can recover the original density of the states of the ErCo2 compound.

Electrical resistivity of the pseudo-binary compound Ce(Fe0.8Al0.2)2

Abstract Electrical resistivity measurements on the alloy Ce(Fe 0.8 Al 0.2 ) 2 as a function of temperature in the range of 1.5 to 300 K shows that the long range magnetic order of the CeFe 2 is destroyed and that the spin glass phase appears with a negative coefficient of T 3/2 . The high residual resistivity is also discussed.

Spin reorientation in Al/Metglas 2605S2/Al trilayers induced by magnetoelastic effect

Mossbauer spectroscopy, in a broad temperature interval of 12–425 K, has been applied to investigate the spin reorientation dynamics caused by the temperature induced magnetoelastic effect on Al(x μm)/Metglas 2605S2 (20 μm)/Al(x μm) trilayers (x=0; 2.5; 5 and 20). It was found that the angle between the average sample magnetization and gamma ray direction (perpendicular to the sample plane) depends on the Al layer thickness. For temperatures smaller than 260 K, saturation of spin reorientation, which can be controlled by adjusting the Al thickness, was reached for Al thicknesses larger than and equal to 5 μm. For a 20 μm Al thickness, changes in the F57e atom spin and charge densities have also been observed. A simple spin model has been proposed to describe qualitatively the spin reorientation effect as well as the influence of the Al thickness on the spin reorientation sensitivity.