S. Murayama

Structural and magnetic properties of NixFe1-x evaporated thin films

Abstract Thin Ni x Fe 1- x alloy films of various compositions ( x x > 0.46) were vacuum deposited onto quartz crystal substrates by electron beam evaporation. Structural properties of the Ni x Fe 1- x films were obtained by electron microprobe analysis (EPMA), X -ray diffraction and TEM-investigation. Magnetic properties were determined by M ( H , T )- and conversion electron Mossbauer spectroscopic (CEMS) measurements. These gave the concentration dependence of the saturation magnetization M s ( x ) and the mean hyperfine field B hf (x) of the evaporated films. The results are compared to those found for bulk Ni x Fe 1- x alloys and sputtered Ni x Fe 1- x alloys films, which had been investigated by other authors . The comparison of the magnetic behavior of the evaporated and sputtered Ni x Fe 1- x films yields the possibility to discuss more intensively the influence of Ar which had been suggested to be decisive in changing the magnetic properties of sputtered Ni x Fe 1- x films.

Evidence for a high-spin Fe state in fcc Fe1-xNix thin films in the invar region

Fe1-xNix alloy films with compositions in the Invar region (0.32 < x < 0.39) were prepared by simultaneous co-deposition of Ni and Fe under uhv conditions onto quatrz crystal substrates. The structure of the films was obtained by X-ray diffraction, the composition by electronprobe microanalysis (EPMA). The temperature and field dependence of the magnetization M(B, T) was measured for 0 T < B < 1 T between 4.2 and 300 K. After investigating the structural and magnetic properties of the as-prepared Fe1-xNix electron Mossbauer spectra (CEMS) were taken at room temperature for each Fe1-xNix film as-prepared and after annealing It is possible to achieve Fe1-xNix films as-prepared with pure fcc-structure and also mixtures of bcc and fcc phases. As-prepared films show, in contrast to the behavior of bulk Fe-xNix samples, high magnetic saturation moments Ms and and large mean hyperfine-fields Bhf which follow the Slater-Pauling curve. After annealing the films exhibit bulk behavior. We conclude that Fe1-xNix films as prepared are in a magnetic state of the fcc-phase which is probably related to the occurence of γ2-Fe. By annealing the films these states convert into the metastable γ-state of the fcc phase with corresponding changes of the magnetic moment and the mean hyperfine field BBhf.

Magnetism of R2Ni7 and RNi3 (R=Y, La, Ce)

Abstract The temperature and field dependence of magnetization of R2Ni7 and RNi3 (R=Y, La, Ce) have been measured. It has been revealed that Y2Ni7 and YNi3 show weak ferromagnetism, and that La2Ni7 and LaNi3 show susceptibility peaks and metamagnetic transitions. Such behavior may be connected with the band structure. Ce2Ni7 shows very weak ferromagnetism, and CeNi3 shows Pauli paramagnetism.

Muon spin rotation and relaxation in CeAg and CeAg0.97In0.03

Abstract Muon spin rotation and relaxation are measured in CeAg and CeAg 0.97 In 0.03 which exhibit a structural phase transition from cubic to tetragonal symmetry. Strong magnetic anisotropy seems to be induced around and below the transition temperature in CeAg, but not in CeAg 0.97 In 0.03 .

μSR study of fcc Fe100−xNix invar and non-invar alloys

Abstract Zero- and transverse-field μSR has been measured on fcc Fe 66 Ni 34 invar and Fe 50 Ni 50 non-invar alloys. For the non-invar alloy the muon spin relaxation follows a single exponential fitting above T c and the muon spin precession has been observed below T c as it is seen in typical ferromagnets. For the invar alloy the relaxation shows a stretched exponential behavior above T c and sharp decrease of the initial asymmetry without the precession has been observed below T c . These facts seem microscopically consistent with the existence of the inhomogeneous magnetic structure for Fe 66 Ni 34 below and above T c . They can also suggest the reduction of the local moment and/or the spin correlation above T c compared with Fe 50 Ni 50 .

AC susceptibility of anisotropic spin glasses ZnMn

Abstract Longitudinal (| c ) and transverse (⊥ c f) ac susceptibility has been studied for Ising-type ZnMn single crystal. We find χ maximum at 0.53 K and very weak χ ⊥ maximum at 0.10 K. It might be possible that two-stage transition P-L-LT occurs as was suggested by mean field theories.

μSR study of uniaxially anisotropic spin-glass ZnMn

Abstract Zero-field muon spin relaxation measurements have been performed on uniaxially anisotropic spin-glass ZnMn with 270 and 600 ppm Mn. Anomalies in the temperature dependence of the relaxation have been observed in each sample. These behaviors are considered to be an indication of the two successive transitions in the anisotropic spin-glass suggested by recent susceptibility measurements.

Critical Behavior of the Uniaxially Anisotropic Spin Glass ZnMn

Critical behaviors of the nonlinear susceptibility in spin glasses have been extensively studied by various experiments and numerical calculations. It has been suggested from both experimental (1,2) and theoretical (3) points of view that the anisotropy in real systems plays an important role for the presence of spin-glass transition and the scaling behavior in the nonlinear susceptibility. Recently, we have studied the uniaxially anisotropic spin-glass ZnMn (4,5) over a wide range of the Mn impurity concentration. Since in ZnMn it is possible to control the ratio of the anisotropy to the variance of the random exchange interaction (D/J) by changing the Mn concentration, systematic study for the effect of the uniaxial anisotropy D on the spin-glass critical behavior could be done in this system.

Coexistence of ferro- and antiferromagnetism in a mixed system Ce1−xNdxAg with CsCl structure

Abstract Neutron diffraction measurements have been performed on the mixed system Ce 1 − x Nd x Ag in the intermediate concentration range. Double magnetic transition occurs for 0.5 x