Solid State Phenomena Vol. 190

Abstract: Local and crystalline structures of as-cast SmCo_5±x alloys subjected to various heat treatments were studied using EXAFS, X-ray diffraction, and metallographic analyses. XRD and EXAFS analyses of SmCo_5-x alloys show the evidence of the Sm-enrichment of the SmCo₅ phase. The behavior of the lattice parameters of SmCo₅ phase in Sm-rich alloys during aging between 1120°C and 700°C can be related to the phase transformation of SmCo₅ into SmCo_5-x phases.

Abstract: Physical properties of the Sm_0.2Gd_0.8Ni₄B compound have been investigated by means of the X-ray powder diffraction, DC and AC-susceptibility techniques. The compound studied crystallizes in CeCo₄B type structure with P6/mmm space group. The unit-cell parameters a and c are determined as 5.01 and 6.95 Å, respectively, and the unit-cell volume V is calculated as 151.08 ų. DC and AC magnetic measurements present the visible magnetic phase transition from paramagnetic to ferromagnetic, around definite transition temperature. The magnetic phase transition temperature of the compound is obtained from DC magnetization, AC-susceptibility and the well known Kouvel-Fisher method as 36.6, 35.7 and 35.2 K, respectively. The saturation magnetization (Ms) and the coercive fields (Hc) of the compound are found to be 3.7µ_B/f.u and 277 Oe, respectively, by using the hysteresis loops at 9.5 K. We have also investigated the non-linear AC-susceptibility of the compound, around its ferromagnetic transition temperature, as a function of temperature, frequency and amplitude of the AC-driving field. In order to explain the measured experimental results, we have used the theory developed for ferromagnetic, based upon the mean field model. The measurements exhibit both frequency and amplitude dependencies. Observed dependencies are compared with the existing theories of linear and nonlinear susceptibilities with reference to short- and long-range interactions. In Kouvel-Fisher method, one plots 1/χ₁*(dχ^-1/dT) against T, obtaining a straight line. The slope of this line gives the critical exponent γ, and it intersects the T axis at Tc. In order to obtain dχ^-1/dT and the best straight line, we used a two-point numerical differentiation program and linear regression method, respectively. The critical exponent γ of the sample is calculated to be 2.78 ± 0.05. The value of the critical exponent β, which is characteristic of static phase transition to a ferromagnetic state, is estimated as 2.41±0.3 from the slope of the line obtained the plot of the absolute third-harmonic values versus the reduced temperature on a log–log scale.

Abstract: The results of magnetization measurements on Ti₃Al intermetallic depending on deuterium concentration as well as structural changes caused by plastic deformation of Ti₃Al deuterides are reported. It was found that the increasing of deuterium concentration leads to the Ti₃Al samples magnetization growth. Magnetization of deformed deuterides decreases with the increasing deuterium concentration. Possible reasons for such magnetization behaviour are discussed.

Abstract: sup>119Sn Mössbauer spectroscopy was used to study the transition from single-ion Kondo behavior in the magnetically ordered state in the heavy-fermion intermetallic СePdSn. Found that the temperature evolution of the experimental spectra agrees with the calculations within the two-level relaxation model. This allows one to treat magnetic structure of CePdSn as the decomposition of the total volume of the СePdSn sample into the antiferromagnetic domains. The temperature dependence of the frequency of fluctuations of the domains magnetization and the distribution density of itinerant electrons near the tin atoms in the process of RKKY interaction are investigated.

Abstract: The comprehensive study of transverse magnetoresistance (MR) and magnetization has been carried out on the high quality single crystals of PrB₆ in the wide range of temperatures 2-40K and magnetic fields up to 80kOe. In order to estimate the role of boron vacancies in the formation of the new spin-glass (SG) phase detected by Alekseev et al. below 20K the experiments were carried out on the ordinary (initial state) and annealed single crystals of PrB₆. The data obtained demonstrate the appearance of spontaneous magnetization below T_SG21.3K with M~1.6 emu/mol for initial state and the absence of spontaneous magnetization for the annealed PrB₆ samples. On the contrary, quite similar behavior of MR was detected for various samples of PrB₆. Our results suggest the existence of the aggregated boron vacancies which provoke the new SG phase formation in PrB₆ at T_SG.

Abstract: Samples of MnGe and CoGe having cubic B20 structure were prepared at high pressure. Magnetic measurements showed that CoGe is a Pauli paramagnet, but MnGe exhibits antiferromagnetic-type ordering below T_N = 175 K. The magnetic susceptibility of MnGe follows a Curie-Weiss law above 300 K with an effective magnetic moment µ_eff = 3.68 µ_B/f.u. and θ_p = + 231 K. The large positive value of θ_p indicates a strong ferromagnetic exchange. The value of the effective moment is close to the free Mn⁴⁺ ion (⁴F_3/2) value 3.87 µ_B/f.u. From measurements of the magnetization of MnGe in fields up to 60 kOe and in the temperature range 2-350 K, we constructed its T-H magnetic phase diagram which is similar to that proposed for MnSi-type compounds with helical magnetic order. Specific heat measurements reveal that the total magnetic entropy of MnGe relative to nonmagnetic CoGe is equal to 3.55 J/mole-K (0.62Rln2).

Abstract: Review of common magnetic and related investigations on the uranium semimetallics and the rare earth intermetallics and their hydrides carried out by K.P. Belov, his students and coworkers as well as by the scientists from Wroc³aw (W. Trzebiatowski's students) is presented.

Abstract: The ferromodulation effect response model of an anisotropic soft magnetic film placed in the crossed permanent bias and alternating excitation magnetic fields is built. It was shown theoretically and experimentally how such a field configuration can be used for registering the effects relating to the film magnetic anisotropy properties.

Abstract: The magnetic properties of alloy containing Fe and 30%Cr, 15 % Co with addition of 3 % Mo after cold rolling were analyzed. It was shown that Hc of Fe-Cr-Co-Mo alloys with cubic texture of recrystallization increases up to 30 %: Hc = 76 kA/m. It was concluded that additional reserves of magnetic properties are created with a more perfect crystallographic and magnetic texture during the recrystallization process.

Abstract: Ni₈₀Fe₂₀/Cu composite wires were produced under torsion using electrodeposition method. The total length of the magnetic film deposited onto 50 µm Cu wire is 3 cm and the thickness of the magnetic layer is about 10 µm. All samples showed single peak in magnetoimpedance (MI) curves. The magnitude (ΔZ/Z) % are 260%, 235% and 119% for samples produced under 22.4, 44.8, 89.7 rad/m torsion values, respectively at driving frequency of 160 kHz. MI effect magnitude decreases with increasing applied torsion during the electrodeposition process. A linear change in the second harmonics of output voltage from wire ends as a function of applied magnetic field (coil-less fluxgate effect) was observed in all sample. The sensitivity of coil-less output increases with increasing torsion and maximum sensitivity was observed in the sample produced at 89.7 rad/m torsion.