Y. Shiokawa

Spin-glass behaviour with extended short-range ferromagnetic order in U2RhSi3

For U2RhSi3, which crystallizes in a disordered derivative of the hexagonal AlB2-type structure, we present a detailed investigation of magnetic properties by measurements of AC and DC susceptibility, magnetization, magnetic relaxation, specific heat and electrical resistivity. The results provide evidence for the formation of extended short-range ferromagnetic order at the temperature TC25 K, as indicated by a specific heat anomaly, and for a low-temperature spin-glass state with a freezing temperature Tf = 19.6 K. According to systematic specific heat experiments on isostructural spin-glass systems, short-range ferromagnetic correlations above the spin-freezing temperature are observed in U2RhSi3 (TC25 K, Tf = 19.6 K) and U2CoSi3 (TC10 K, Tf8 K), but not in U2PdSi3 (Tf = 13.5 K) and U2NiSi3 (Tf22 K). Different degrees of structural disorder of transition metal and silicon atoms, both on the same crystallographic site, seem to be the origin for the distinct different magnetic behaviour.

Magnetic properties of Lu2Fe17 crystals

Abstract We present the results of crystal structure and magnetization studies of three single crystals grown from melts of different nominal compositions in the vicinity of the Lu2Fe17 stoichiometry. The ferromagnetic state of the crystals is strongly dependent on the real sample composition and the local atomic ordering. A drastic difference is observed in the behaviour of the ferro–antiferromagnetic transition, even in crystals for which almost identical composition and crystal parameters were determined by microprobe and X-ray analysis.

Preparation of high purity uranium metal from aqueous solutions

Abstract The uranium amalgam was quantitatively prepared by electrolysis from the aqueous solution containing acetic acid and sodium acetate using a mercury cathode. A bright button or brown porous one of uranium metal was obtained by thermal decomposition of the amalgam. The purity was found to be much higher than commercial grade metal of ca. 99.95%. As a result of this work, the simple and easy procedure for preparation of uranium metal with a high level of purity on the laboratory scale has been developed.

Spin-glass behavior with short-range antiferromagnetic order in Nd2AgIn3

We present experimental results of complex susceptibility, static magnetization, magnetic relaxation, specific heat, and electrical resistivity measurements on an intermetallic compound Nd2AgIn3. The results indicated that Nd2AgIn3 undergoes a spin-glass transition at a freezing temperature Tf=12.6 K accompanied with the formation of short-range antiferromagnetic order. The mechanism of formation of spin-glass state in Nd2AgIn3 is different from that in diluted metallic spin-glass or uranium intermetallic compound. The existences of frustrated moments due to the triangles of nearest neighbors in Nd atomic layers and randomly distributed Ruderman–Kittle–Kasuya–Yosida interactions may be responsible for the spin glass state formed in Nd2AgIn3.

Specific-heat anomaly of metamagnetism on PrFe4P12 and UCoAl

Abstract The field dependence of specific heat has been measured at low temperatures in order to study two different types of f-electron metamagnetic systems. The antiferromagnet PrFe4P12 with Neel temperature of 6.4 K shows a sharp peak structure in C/T at the spin flip metamagnetic transition. In the high field state, the magnetic contribution Cm/T shows an anomalous huge value ∼1.4 J/K 2 mol . UCoAl shows the metamagnetic transition from paramagnetic ground state at ∼1 T, where C/T at 0.5 K shows an apparent decrease reflecting a change of the density of states. In the low-field state, ferromagnetic spin-fluctuation dominates in an anomalous temperature dependence of C.

Spin-glass behavior in U2PtSi3

Abstract We present the DC magnetization, specific heat and magnetic relaxation measurements on well-annealed polycrystal-line sample of U 2 PtSi 3 . All the main characteristics of spin-glass behavior are observed. They are: (1) frozen-in magnetic moments below a freezing temperature T f and, hence, a peak in the field-dependent magnetization; (2) absence of visible singularity in temperature dependence of specific heat at T f ; (3) irreversibility in magnetization below T f ;(4) remanent magnetic relaxation on macroscopic time scales after changing the magnetic field below T f . The spin-glass state in U 2 PtSi 3 at low temperatures is considered to originate from the randomly frustrated U-U interactions resulting from the disordering of Pt and Si atoms on the crystallographic sites.

Magnetic properties of the UCo1−xTxAl solid solutions (T=Rh and Ir)

Abstract Results of crystal-structure and magnetic studies of solid solutions between a 5f-band metamagnet UCoAl and ferromagnets URhAl and UIrAl are reported. The UCo1−xRhxAl system exhibits a continuous solubility with a monotonous dependence of lattice parameters. For the UCo1−xIrxAl compounds we observe this behaviour only for concentrations close to parent compounds, i.e. at x≤0.2 and x≥0.8, leaving the alloys with intermediate concentrations structurally heterogeneous. In the common solubility region lattice parameters in both systems are nearly identical. Also in magnetism, Rh and Ir substitutions for Co yield analogous effects. Ferromagnetism is stabilised for x≥0.1 and the Curie temperature and the spontaneous moment exhibits qualitatively similar concentration dependence. These results imply similar evolution of electronic structure involving variations of the 5f-ligand hybridization due to Rh and Ir substitutions.

Stoner gap in the superconducting ferromagnet U Ge 2

We report the temperature

Spin-glass-like behavior of ternary uranium compound U2AuSi3

(T)

Magnetic, transport, and thermal properties of ternary intermetallic compound Nd2PtSi3

dependence of ferromagnetic Bragg peak intensities and dc magnetization of the superconducting ferromagnet