Comparison of Magnetic and Electrical Properties in Amorphous, Quasicrystalline and Crystalline States of Al-Mn Alloys

The magnetic and electrical properties in the amorphous, quasicrystalline and crystalline states of Al-Mn and Al-Mn-Si alloys have been investigated and compared because the amorphous structure is often correlated with the icosahedral structure, and the structures of some crystalline compounds are resemble to that of the quasicrystalline alloys. The magnetizations measured up to 300 kOe for the amorphous alloys are slightly larger than those of the quasicrystalline alloys, and the paramagnetic Curie temperature of the former alloys is larger than that of the latter alloys. The magnitude of effective magnetic moment P_ determined from the Curie-Weiss law for crystalline alloys is qualitatively explained in terms of the Pauling valence. The value of P_ of the quasicrystalline alloys is almost the same as that of the amorphous ones and about two times that of the crystalline alloys at the same composition. From the magnetic measurements it becomes clear that Mn sites are partly magnetic, and the magnetic properties are drastically modified by substituting some fraction of Mn for other transition metals such as Cr. The spin-glass behavior is observed and the spin freezing temperature lies on the same line as a function of Mn content for both the amorphous and quasicrystalline alloys. The electrical resistivity of the quasicrystalline alloys with a relatively high Mn content is extremely large accompanying a negative temperature coefficient as that of the amorphous alloys. After crystallization, its magnitude is reduced drastically and the temperature dependence curves of the alloys with high concentrations show a positive curvature in the wide temperature range. Therefore, the magnitude and the temperature dependence of electrical resistivity of the quasicrystalline alloys are very different from those of the crystalline alloys. From these results, it is concluded that the magnetic and electrical properties of Al-Mn quasicrystalline alloys are very similar to those of amorphous ones and distinctly different from those of the crystalline alloys

Elinvar Characteristics of Amorphous Alloys and Their Applications

The elastic properties and the Elinvar characteristics of various kinds of amorphous alloys are introduced. The Elinvar characteristics of Fe-base ferromagnetic amorphous alloys arises from their large ΔE effect. The elastic properties are sensitively affected by the internal stress, and the Elinvar characteristics is also obtained even in nonferromagnetic amorphous alloys such as Pd-Si and Ni-Si-B alloy systems by annealing or cold-rolling. A large stiffening is observed in Fe-base amorphous alloys in the saturated magnetic field, being different from the pole effect. The applications of the amorphous Elinvar alloys to mechanical vibrators and delay lines are described as examples, and then the merits and problems for their applications are pointed out from the practical point of view

Refrigerant Characteristics of R-Al and R-Si Amorphous Alloys((A)Amorphous Alloys)

R-Al and R-Si amorphous ribbon and powder samples were prepared by melt-quenching and mechanical grinding, respectively, in order to investigate the refrigerant characteristics. The magnetic transition temperature is selected without difficulty because the alloy composition in the amorphous state is not restricted by the stoichiometric composition. The magnetic entropy change of Dy-Al and R-Si amorphous alloys shows a broad maximum around the transition temperature, which is advantageous for a wide temperature span of refrigeration. The softening of those amorphous alloys below the crystallization temperature is useful for the purpose of static consolidation. The Debye temperature is increased by addition of B

Magnetization and AC-Susceptibility of Fe-Zr Amorphous Alloys

Measurements of magnetization and ac-susceptibility of Fe-Zr amorphous alloys over the wide composition range have been carried out. The spin glass like behavior appears in two different regions of composition. The spin glass behavior in Fe-rich Fe amorphous alloys (around 90 at.% Zr) is due to the frustration of antiferromagnetic coupling between spins. The other behavior around 50 at.% is due to the dilution of atoms with magnetic moment. They are explained by the local environment effect

Soft Magnetic Co-Ti-B Amorphous Alloys with High Corrosion Resistance

Co-Ti-B ternary amorphous ribbons were prepared by the melt-quenching method, and their soft magnetic properties, hardness and corrosion resistance have been investigated. With increasing titanium content, the Curie temperature decreases monotonically, while the crystallization temperature gradually increases. These alloys are magnetically very soft, that is, the coercive force takes a minimum value of 0.01 Oe and the maximum permeability shows a large value of 6×10^4 around x=0.05 for (Co_Ti_x)_B_ amorphous alloys. Their linear magnetostrictions are also quite small, being of the order of about -2.5×10^. In addition, these amorphous alloys have a high hardness and an excellent corrosion resistance. Therefore. Co-Ti-B amorphous alloys are promised as the soft magnetic materials for electromagnetic devices

Invar-Type New Ferromagnetic Amorphous Fe-B Alloys(Physics)

Measurements of magnetization, electrical resistivity, thermal expansion and differential thermal change were made on amorphous Fe_B_x (9≦X≦21) alloys prepared by rapid quenching from the liquid state. With decreasing boron content in the alloys, the Curie temperature falls remarkably, while the magnetic moment increases sluggishly. The thermal expansion curves exhibit the invar characteristics below the Curie temperature due to a large positive spontaneous volume magnetostriction, and the reduced magnetization curves decrease much more rapidly with increasing temperature than those of other ferromagnetic amorphous alloys

Electrical Resistivity and Its Temperature Dependence of Al-base Quasicrystalline and Crystalline Alloys

Al-Mn and Al-Cr quasicrystalline and Al-Mn crystalline alloys were prepared by melt-quenching and their electrical resistivities were studied. The quenched samples exhibited an extremely high resistivity because of nonperiodic potential scattering and resonance scattering of the Fermi electrons. The temperature dependence of electrical resistivity of Al-22.5%Mn quasicrystalline was tried to fit by several models, and it was found that the plots of lnT (from 4.2 to 20 K) and T^2 (from 20 to 60 K) showed a straight line. The electrical resistivity of Al_6Mn crystalline alloy showed a linear temperature dependence over wide high temperatures, but that of Al_4Mn crystalline alloy showed a deviation from the linearlity. The values of P of the quasicrystalline alloys were larger than those of the crystalline counterparts

Hydrogenation of Amorphous and Crystalline Gd-Co Alloys

Amorphous Gd-Co alloys were prepared over a wide composition range from 45 to 70 at % Gd by melt-quenching. These alloys absorbed a large amount of hydrogen in the amorphous state below 423 K. The hydrogen absorption capacity for the amorphous alloys was lower than that for the corresponding crystalline alloys and it increased with increasing Gd content in the alloy. The number of hydrogen atom absorbed per one gadolinium atom was approximately two with regardless to the alloy composition. On the other hand, the Laves phase compound GdCo_2 was changed to an amorphous phase after reaction with hydrogen below about 700 K, among all of intermetallic compounds formed in Gd-Co system. This amorphous alloy did not show a pressure plateau in the pressure-composition isotherm, in the same manner as other melt-quenched amorphous alloys

Giant Magnetoresistance in Bulk, Liquid-quenched Ribbon and Film Granular Alloys

Magnetoresistance has been investigated for bulk, liquid-quenched ribbon and film noble metal(NM)-rich granular alloys. Solid solutions were obtained in the water- , liquid- and vapor-quenched state and nano-structured magnetic precipitates in NM-rich matrix were evolved by subsequent heat treatments. After aging, the giant magnetoresistance (GMR) is observed in these bulk, liquid quenched ribbon and film granular alloys. In particular, the room temperature value of Magnetoresistance (MR) ratio of 5 % in the Co_Au_ bulk granular alloy aged at 300 ℃ for 1 h is larger than that reported in Co/Au multilayers. The Co_Cu_ alloy ribbons aged at 500 ℃ for 90 min exhibits the MR ratio as large as 6.3 % at room temperature in a field of 15 kOe. Small amounts of Ni improve the MR ratio. Especially, the Co_Ni_5Cu_ alloy ribbons aged at 500 ℃ for 60 min exhibits the ratio of 7.6 % larger than the value of the aged Co_Cu_ ribbon. Furthermore, the anisotropy in GMR in bulk Fe_5Ni_Cu_ alloy aged at 500 ℃ for 170 min is obtained by compression