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1.
Igor Dubenko Tapas Samanta Arjun Kumar Pathak Alexandr Kazakov Valerii Prudnikov Shane Stadler Alexander Granovsky Arcady Zhukov Naushad Ali 《Journal of magnetism and magnetic materials》2012
The studies of magnetocaloric properties, phase transitions, and phenomena related to magnetic heterogeneity in the vicinity of the martensitic transition (MT) in Ni–Mn–In and Ni–Mn–Ga off-stoichiometric Heusler alloys are summarized. The crystal structure, magnetocaloric effect (MCE), and magnetotransport properties were studied for the following alloys: Ni50Mn50−xInx, Ni50−xCoxMn35In15, Ni50Mn35−xCoxIn15, Ni50Mn35In14Z (Z=Al, Ge), Ni50Mn35In15−xSix, Ni50−xCoxMn25+yGa25−y, and Ni50–xCoxMn32−yFeyGa18. It was found that the magnetic entropy change, ΔS, associated with the inverse MCE in the vicinity of the temperature of the magneto-structural transition, TM, persists in a range of (125-5) J/(kg K) for a magnetic field change ΔH=5 T. The corresponding temperature varies with composition from 143 to 400 K. The MT in Ni50Mn50−xInx (x=13.5) results in a transition between two paramagnetic states. Associated with the paramagnetic austenite-paramagnetic martensite transition ΔS=24 J/(kg K) was detected for ΔH=5 T at T=350 K. The variation in composition of Ni2MnGa can drastically change the magnetic state of the martensitic phase below and in the vicinity of TM. The presence of the martensitic phase with magnetic moment much smaller than that in the austenitic phase above TM leads to the large inverse MCE in the Ni42Co8Mn32−yFeyGa18 system. The adiabatic change of temperature (ΔTad) in the vicinity of TC and TM of Ni50Mn35In15 and Ni50Mn35In14Z (Z=Al, Ge) was found to be ΔTad=−2 K and 2 K for ΔH=1.8 T, respectively. It was observed that |ΔTad|≈1 K for ΔH=1 T for both types of transitions. The results on resistivity, magnetoresistance, Hall resistivity in some In-based alloys are discussed. 相似文献
2.
ABSTRACTCrystal structure, microstructural chemical analysis, magnetic properties and magnetocaloric effect for ‘as cast’ and annealed Gd4?xTbxCo3 (x?=?0–4) were investigated. Only Gd4Co3 was homogeneous and crystallised in the hexagonal Ho4Co3-type of crystal structure. Samples substituted with terbium proved to be a mixture of (Gd,Tb)12Co7 and (Gd,Tb)Co2 phases. With the increase of terbium content the entropy change increased and for the samples with x?=?3, 4 reached the highest values. Even ‘as-cast’ samples exhibit pronounced values of the magnetocaloric parameters. 相似文献
3.
Nuclear magnetic moments provide a sensitive test of nuclear wave functions, in particular those of neutrons, which are not
readily obtainable from other nuclear data. These are taking added importance by recent proposals to study parity non-conservation
(PNC) effects in alkali atoms in isotopic series. By taking ratios of the PNC effects in pairs of isotopes, uncertainties
in the atomic wave functions are largely cancelled out at the cost of knowledge of the change in the neutron wave function.
The Bohr–Weisskopf effect (B–W) in the hyperfine structure interaction of atoms measures the influence of the spatial distribution
of the nuclear magnetization, and thereby provides an additional constraint on the determination of the neutron wave function.
The added great importance of B–W in the determination of QED effects from the hfs in hydrogen-like ions of heavy elements,
as measured recently at GSI, is noted. The B–W experiments require precision measurements of the hfs interactions and, independently,
of the nuclear magnetic moments. A novel atomic beam magnetic resonance (ABMR) method, combining rf and laser excitation,
has been developed for a systematic study and initially applied to stable isotopes. Difficulties in adapting the experiment
to the ISOLDE radioactive ion beam, which have now been surmounted, are discussed. A first radioactive beam measurement for
this study, the precision hfs of 126Cs, has been obtained recently. The result is 3629.515(∼0.001) MHz. The ability of ABMR to determine with high precision nuclear
magnetic moments in free atoms is a desideratum for the extraction of QED effects from the hfs of the hydrogen-like ions.
We also point out manifestations of B–W in condensed matter and atomic physics.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
4.
Svalov A. V. Arkhipov A. V. Lepalovskii V. N. Stepanova E. A. Vas’kovskii V. O. Kurlyandskaya G. V. 《Physics of the Solid State》2021,63(10):1553-1557
Physics of the Solid State - The results of the study of the magnetic and magnetocaloric properties of amorphous Gd–Co ferrimagnetic films possessing perpendicular magnetic anisotropy in a... 相似文献
5.
The magnetic and structural properties of a series of nonstoichiometric Ni–Mn–Ga Heusler alloys are theoretically investigated in terms of the density functional theory. Nonstoichiometry is formed in the coherent potential approximation. Concentration dependences of the equilibrium lattice parameter, the bulk modulus, and the total magnetic moment are obtained and projected onto the ternary phase diagram of the alloys. The stable crystalline structures and the magnetic configurations of the austenitic phase are determined. 相似文献
6.
ABSTRACT The evolution of deformation texture and microstructure in commercially pure Al (cp-Al) and two Al–Mg alloys (Al–4Mg and Al–6Mg) during cold rolling to a very large strain (true strain εt? ≈?3.9) was investigated. The development of deformation texture in cp-Al, after rolling, can be considered as pure metal or Copper-type, which is characterised mainly by the presence of Cu {112}<111>, Bs {110}<112> and S {123}<634> components. The deformation microstructure clearly indicates that deformation mechanism in this case remains slip dominated throughout the deformation range. In the Al–4Mg alloy, the initial slip mode of deformation is finally taken over by mechanism involving both slip and Copper-type shear bands, at higher deformation levels. In contrast, in the Al–6Mg alloy, the slip and twin mode of deformation in the initial stage is replaced by slip and Brass-type shear bands at higher deformation levels. Although a Copper-type deformation texture forms in the two Al–Mg alloys at the initial stage of deformation, there is a significant increase in the intensity of the Bs component and a noticeable decrease in the intensity of the Cu component at higher levels of deformation, particularly in the Al–6Mg alloy. This phenomenon indicates the possibility of transition of the deformation texture from Cu-type to Bs-type, which is concurrent with the addition of Mg. Using visco-plastic self-consistent modelling, the evolution of deformation texture could be simulated for all three materials. 相似文献
7.
《Journal of magnetism and magnetic materials》2002,251(1):61-73
The proposal involves a heat-pumping scheme based upon the first-order antiferromagnetism–ferromagnetism transition in FeRh alloy. Using the model S–T diagram for this alloy, the heat-pump cycles, are drawn up based on the transition latent heat absorption and emission when the transition is induced by applying magnetic field. The calculated values of heat coefficient ϕ for the cycles are ∼39 at ΔT=5 K and ∼30 at ΔT=10 K, where ΔT is the difference between the temperature surrounding and that of the heat receiver. These values are achieved using the comparatively low magnetic fields of ∼2×106 A m−1. The high values of ϕ, together with high value of cooling capacity, make it possible to consider Fe–Rh alloys as an effective magnetic heat-pump working body near the room temperature. 相似文献
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9.
Canan Aksu Canbay Soner Ozgen Zuhal Karagoz Genc 《Applied Physics A: Materials Science & Processing》2014,117(2):767-771
There are many studies to improve the properties of Cu–Al–Mn shape memory alloys, such as high transformation temperatures, ductility and workability. Most of them have been performed by adding a quaternary component to the alloy. In this study, the effect of trace Mg addition on transformation temperatures and microstructures of three different quaternary Cu–Al–Mn–Mg alloys has been investigated using thermal analysis, optical microscopy and XRD techniques. The transformation temperatures are within the range of 120–180 °C, and they have not changed significantly on decreasing the Mn content, replacing with Mg. The fine precipitates have been observed in the alloys with the Mg content up to 1.64 at%. Calculated entropy change and XRD analysis reveal that the alloys with high Al content have mainly 18R-type structure which could be responsible for good ductility and workability. 相似文献
10.
Y. Shimpo H. Seki A. Wongsatanawarid S. Taniguchi T. Maruyama T. Kurita M. Murakami 《Physica C: Superconductivity and its Applications》2010,470(20):1170-1172
Since bulk Y–Ba–Cu–O superconductors are brittle ceramics, reinforcement of mechanical properties is important for practical applications. It has been reported that bulk Y–Ba–Cu–O can be reinforced with Al or Fe based alloy ring, in that compression force acts on bulk Y–Ba–Cu–O due to a difference in thermal expansion coefficients. However, the shrinkage of the metal ring was not so large, and therefore careful adjustment of the circumference of the bulk and the metal rings was necessary. In this study, we employed Fe–Mn–Si shape memory alloy rings to reinforce bulk Y–Ba–Cu–O. The advantage of the shape memory alloy is that the shrinkage can take place on heating, and furthermore, the alloy shrinks and compresses the bulk body on cooling. Bulk Y–Ba–Cu–O superconductor 22.8 mm in diameter was inserted in a Fe–Mn–Si ring 23.0 mm in inner diameter at room temperature. Beforehand, the Fe–Mn–Si ring was expanded by 12% strain at room temperature. Then the composite was heated to 673 K. At room temperature, the Fe–Mn–Si ring firmly gripped the bulk superconductor. We then measured trapped fields before and after the ring reinforcement, and found that the trapped field was improved through the treatment. 相似文献
11.
《Journal of Electron Spectroscopy and Related Phenomena》1999,105(1):77-84
The electronic structure of the ion-beam-mixed Pd–Au alloys have been studied using valence band spectra of XPS and electron excited CVV–Auger spectra. To show the relationship between the electronic structure changes and the Auger spectral line shape, the data of the self-convolution of the partially weighted valence band spectra was compared with the Auger spectra of Pd–Au alloys. The Pd–Au alloy is one of the systems which both atomic and band-like contributions are evident in the Auger spectral line shape. Since the self-convolution of PDOS’s relates to the band-like part of Auger spectra, in Pd–Au alloys, the band-like structure in the Auger line shape can be classified by the self-convolution of the partially weighted valence band spectra. Finally, we found that the increase in peak size at ∼80 eV with the increase in Pd content is due to the band-like contribution in the Au N6,7VV Auger line shape. 相似文献
12.
《Journal of magnetism and magnetic materials》2001,231(1):20-22
The hyperfine field distributions and the local spin configurations for Fe atoms in the (Pd100−xRhx)90Fe10 alloys for x=0, 10 and 20 are investigated by the Mössbauer spectroscopy technique. It was found that the anomalous behavior of TC in these alloys is attributable to the spin reorientation in some part of Fe atoms with the formation of local antiferromagnetic spin configurations. 相似文献
13.
《Journal of magnetism and magnetic materials》2001,234(1):153-173
The purpose of the present work is a quantitative investigation of the biquadratic exchange interaction effects on the paramagnetic–ferrimagnetic transition arising from two strongly coupled paramagnetic (1-spin) sublattices, of respective moments m and M. The free energy describing the physics of the system is of Landau type. In addition to the quadratic and quartic terms, in both m and M, this free energy involves two mixing interaction terms. The first is a lowest order coupling −CmM, where C<0 stands for the coupling constant measuring the interaction between the two sublattices. While the second, which is relevant for 1-spin systems and which traduces the dipole–dipole (or biquadratic) interaction, is of type wm2M2, where w>0 is the new coupling constant. These two interactions enter in competition, and then, they induce drastic changes of the magnetic behavior of the material. The main change is that, the presence of this high order coupling tends to destroy the ferrimagnetic order of the system. We first show that the introduction of this biquadratic interaction does not affect the values of critical exponents. Also, we find that the compensation temperature (when it exists) and the compensation magnetic field are shifted to their lowest values, in comparison with the w=0 case. The Arrott-phase-diagram shape is also investigated quantitatively. We show the existence of three regimes depending on the values of w. When the latter is small, we find that the region of competition between the coupling C and the applied magnetic field H becomes more narrow under the effect of w (by competition, we mean the passage from the antiparallel state to the parallel one). While for higher values of w, this competition disappears completely, and then, the system loses its ferrimagnetic character. Kinetics of the phase transition is also examined, when the temperature is lowered from an initial value Ti to a final one Tf very close to the critical temperature Tc. As in the w=0 case, we find that kinetics is controlled by two kinds of relaxation times τ1 and τ2. The former is the relevant time, and is associated to long-wavelength fluctuations driving the system to undergo a phase transition. The second is a short time, which controls local dynamics. Near Tc, we show that, in particular, the longest relaxation time τ1 becomes less important in comparison with that relative to the w=0 case. Finally, we note that the existence of two relaxation times is consistent with the predictions of a recent experiment, which was concerned with the 1/2-spin compounds LixNi2−xO2, where the composition x is close to 1. 相似文献
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15.
The study compares the effect of incorporation of three different groups of anti-hyperlipidemic drugs, namely niacin, simvastatin, and fenofibrate on the phase profile of liposomal membranes of dipalmitoylphosphatidylcholine (DPPC). The fluorescence anisotropy studies, using 1,6-diphenyl-1,3,5-hexatriene as fluorescent probe, have shown that the lipophilic molecule fenofibrate changes phase behavior of DPPC liposomal membrane to a greater extent compared to the changes produced by amphiphilic simvastatin and hydrophilic niacin. This variation in effect can be attributed to the nature of the drug molecules and hence their location in different parts of the liposomal membrane. We have also calculated the changes in van’t Hoff enthalpy values in all these three cases and observed that these values decreased with increase in drug concentrations in the case of simvastatin but for fenofibrate and niacin the effect is completely the reverse. In order to get a better insight, the fraction of motionally restricted lipid molecules has been calculated. 相似文献
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17.
Evidence of relaxation has been observed in ferromagnetic Ni–Mn–Ga single crystals. The relaxation may be explained by a change in symmetry-conforming short-range ordering according to Ren and Otsuka in this off-stoichimetric ordered alloy. Martensite stabilization has also been found after martensite ageing. 相似文献
18.
Takeshi Saito Sigurd Wenner Elisa Osmundsen Calin D. Marioara Sigmund J. Andersen Jostein Røyset 《哲学杂志》2013,93(21):2410-2425
Effects of addition of Zn (up to 1 wt%) on microstructure, precipitate structure and intergranular corrosion (IGC) in an Al–Mg–Si alloys were investigated. During ageing at 185?°C, the alloys showed modest increases in hardness as function of Zn content, corresponding to increased number densities of needle-shaped precipitates in the Al–Mg–Si alloy system. No precipitates of the Al–Zn–Mg alloy system were found. Using high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), the Zn atoms were incorporated in the precipitate structures at different atomic sites with various atomic column occupancies. Zn atoms segregated along grain boundaries, forming continuous film. It correlates to high IGC susceptibility when Zn concentration is ~1wt% and the materials in peak-aged condition. 相似文献
19.
C. D. Marioara S. J. Andersen T. N. Stene H. Hasting J. Walmsley A. T. J. Van Helvoort 《哲学杂志》2013,93(23):3385-3413
TEM investigations of two alloys isothermally heat treated at 175°C and 260°C show how Cu additions to the Al–Mg–Si system affect precipitation. Both alloys had a solute content Mg?+?Si?=?1.3 at.%, 0.127 at.% Cu, but with Mg/Si 0.8 and 1.25. Cu-containing Guinier-Preston (GP) zones and three types of Q′ precursors are identified as most common phases at peak-hardness conditions, whereas β″ accounts for maximum 30% of the total number of precipitates. The precursors have needle (L and S precipitates) or plate (C precipitate) morphologies. They consist of different arrangements of Al, Mg and Cu atoms on a grid defined by triangularly arranged Si planes parallel with and having the same period as {100} Al planes. The Si grid is composed of nearly hexagonal sub-cells of a?=?b?=?4.05?Å, c?=?4.05?Å. The Cu arrangement on the grid is often disordered in the needle precursors. The plate precursor is ordered, with a monoclinic unit cell of a?=?10.32?Å, b?=?8.1?Å, c?=?4.05?Å, γ?=?101°. 相似文献
20.
O. S. Kolotov A. V. Matyunin G. M. Nikoladze P. A. Polyakov 《Bulletin of the Russian Academy of Sciences: Physics》2017,81(8):1005-1008
Time dependences of the azimuthal component of the torque T φ(t) acting on magnetization are calculated to understand the nature of the delayed magnetization acceleration effect observed during the 90° pulsed magnetization of real ferrite–garnet films, in which biaxial anisotropy exists alongside with in-plane anisotropy. A calculation technique based on analyzing an operating point trajectory is used. Calculations show that if the effective anisotropy field H K2 is comparable to the magnetizing pulse amplitude H ma, abruptly ascending regions at characteristic times t* in curves T φ(t) arise, in the limit of which nonlinear magnetization oscillations formed. The shape of these regions depends weakly on the magnetizing pulse front duration τf. This explains the reason of the weak dependence of the nonlinear magnetization oscillations on duration of the magnetizing pulse front. Calculations also show that the main features of the delayed acceleration effect are less clear upon an increase of the pulse amplitude: the behavior of curves T φ(t) becomes smoother near times t*, and an increase in the pulse front duration is accompanied by a stronger drop in the intensity of magnetization oscillations. 相似文献