Yoshihito Miyako

Magnetic properties and phase diagram of Ce(Ru1-xRhx)2Si2 (0≤x≤0.5)

Magnetic susceptibility, magnetization and specific heat measurements have been performed on single crystalline Ce(Ru 1- x Rh x ) 2 Si 2 in the Ru rich region(0≤ x 5 T). The AF ordering is destroyed above H C and the system further undergoes a metamagnetic transition at H M .

Nonlinear Susceptibility of a Spin Glass Compound (Ti1-xVx)2O3: II

Linear (χ 0 ) and nonlinear (χ 2 ) susceptibilities of (Ti 1- x V x ) 2 O 3 have been studied in detail around the spin freezing temperature T g . The measurement on single crystal has revealed that both χ 0 and χ 2 are highly anisotropic. The linear susceptibility χ 0 shows a cusp at T g . The nonlinear susceptibility χ 2 , which is observed as the third higher harmonic of the applied ac field ( h = h 0 sin ω t ), shows the very sharp peak in the vicinity of T g . The frequency ν(=ω/2π) and amplitude h 0 dependence of χ 2 has been measured in detail to study the critical behavior around T g in the static limit ν→0 and in the infinitesimal field strength h 0 →0. |χ 2 | increases rapidly with decreasing ν and h 0 , which implies the divergence of χ 2 at T g in the limit ν→0 and h 0 →0.

Nonlinear Magnetization at the Spin Glass Phase Transition Temperature

Nonlinear magnetization, m=χ 0 h+χ 2 h 3 , was found in spin glass using a mutual inductance bridge. The susceptibility χ 0 showed a cusp at T g as usual, on the other hand χ 2 behaved like a divergence at T g .

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.

Canonical spin glass behavior in Ce2AgIn3

A new intermetallic compound Ce 2 AgIn 3 has been prepared and found to crystallize with the hexagonal CaIn 2 -type structure. We report the results of ac and dc magnetic susceptibility (χ ac and χ dc ), specific heat ( C ) and electrical resistivity (ρ) measurements on this compound. At around 1.8 K, the real part in χ ac shows a cusp and the nonlinear part in χ dc diverges, while there are no anomalies in both C and ρ. On the other hand, ρ increases slightly with decreasing temperature below 10 K and C / T at 0.5 K is large at 780 mJ/K 2 mol-Ce. These results indicate that Ce 2 AgIn 3 is a spin glass of good quality and also belongs to the heavy fermion system.

Linear and Non-Linear Susceptibilities in Canonical Spin Glass AuFe (1.5 at.%Fe)

Linear, χ 0 , and nonlinear, χ 2 and χ 4 , susceptibilities were measured in metallic spin glass AuFe. Nonlinear susceptibilities for AuFe (1.5 at.%Fe) diverge at T g showing the power law behavior and the critical behaviors around T g are interpreted by Suzukis theory based on Edwards and Anderson model. The critical exponents γ s , δ and β were obtained to be γ s =1.1±0.2, δ=2.0±0.2 and β∼0.9, respectively.

Long Range Magnetic Order on the Kondo Lattice. SDW in Ce(Ru1-xRhx)2Si2 as Studied by Neutron Diffraction.

We report results of neutron-diffraction experiments which have been carried out to study the long range magnetic order developing on the Kondo lattice of the pseudo-binary-alloy system Ce(Ru 1- x Rh x ) 2 Si 2 with x around 0.15. The ground-state structure of the ordered phase has a sinusoidal modulation of the moment, that is, a modulation with an incommensurable wave number and a uniaxial polarization. We assign this phase to the same category of magnetism as that of the spin-density wave in metals. Several characteristic quantities of this ordering such as the order parameter, the wave number, the amplitude and the anisotropy of the polarization and the anomaly in the lattice-constant are analyzed and discussed in terms of either the s-d model or the hybridized f-band model of Kondo effect.

Spin-glass transition in a magnetic field for canonical spin glasses AuFe and AgMn and the critical phenomena

A magnetic field vs temperature ( H - T ) phase diagram is determined from linear χ ⊥ 0 and nonlinear χ ⊥ 2 susceptibilities perpendicular to H for metallic spin glasses AuFe (4 at.%Fe) and AgMn (4 at.%Mn). Two characteristic temperatures T 1 ( H ) and T 2 ( H ) in the H - T phase diagram are obtained from the measurements of χ ⊥ 0 and χ ⊥ 2 . The σ ⊥ 2 signal has a round maximum at T = T 1 ( H ) and below T 1 ( H ) the imaginary part of χ ⊥ 0 increases rapidly around T = T 2 ( H ). The critical exponents β and γ are found to be β=1.0±0.2, γ=2.0±0.2 for AuFe (4at.%Fe) and β=1.0±0.2, γ=1.7±0.2 for AgMn (4 at.%Mn) from the scaling argument. Nonlinear magnetization far above T g is discussed with the Sherrington-Kirkpatrick (SK) model including an additional atomic short-range effect.

Electron Spin Resonance of Cr3+ Ions Coupled with Oxygen Vacancies in Rutile

Paramagnetic resonance of Cr 3+ spins in TiO 2 single crystals were investigated in detail and two sets of weak absorption signals were observed in addition to usual Cr 3+ resonance lines. By analysing both the directions of the local symmetry axes and the magnitude of spin Hamiltonian parameters D and E of these two groups I and II, it is concluded that these resonances come from substitutional Cr 3+ spins coupled with the second and the third neighbor oxygen vacancies respectively. Spin Hamiltonian parameters determined for each group are given by

Magnetic and electrical properties of the U-Si system (part II)

Abstract Compounds in the U-Si system were found to be classified into three groups; the paramagnetic heavy-fermion system (U 3 Si 5 ; γ = 120mJ/K 2 U-mol), the ferromagnet (USi; T c = 127K, μ 0 = 0.1μ B ) and Pauli paramagnetic metals (U 3 Si, U 3 Si 2 , USi 3 ).