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1.
Magnetic susceptibility and electrical resistivity measurements were performed (Pd100?xCox)80P20 alloys where 15 < x < 50. The magnetic properties show that these alloys undergo a ferromagnetic transition between 272 and 399 K as the cobalt concentration increases from 15 to 50 atomic %. Below 20 atomic % Co the short-range exchange interactions which produce the ferromagnetism are unable to establish a long-range magnetic order and a peak in the magnetization shows up at the lowest temperature range under an applied field of 6.0 kOe. The electrical resistivity of these alloys has been measured from 4.2 K up to the vinicity of the melting point (900 K). The electrical resistivity data could be interpreted by the coexistence fo a Kondo-like minimum and ferromagnetism. The minimum becomes less important as the transition metal concentration increases. The coefficients of In T and T2 become smaller and concentration dependent. The spin ordering in such alloys can be simulated as either the ordering due to an applied “external field” or as an increase in “internal fields”. These are due to an increase in transition metal concentration. The negative magnetoresistivity is a strong indication of the existence of localized moment.  相似文献   

2.
Physical properties of TmPtIn have been investigated by means of magnetic, electrical transport, calorimetric as well as neutron diffraction measurements. The compound crystallizes in the hexagonal ZrNiAl-type crystal structure. It orders antiferromagnetically below TN = 3.5 K with the Tm magnetic moments confined to the basal hexagonal plane. They form a non-collinear “triangular” magnetic structure that may be described by the propagation vector . At 1.6 K, the Tm magnetic moment is equal to 5.59(9)μB. The antiferromagnetic character of the electronic ground state is reflected in the low temperature behaviors of the magnetic susceptibility and the specific heat, which may be described by spin-wave theory of antiferromagnetic magnons with linear dispersion relation. The compound exhibits metallic character of electrical conduction.  相似文献   

3.
From X-ray Guinier powder data the crystal structures of the ternary germanides Ce(Rh or Ir)Ge and Ce(Pd or Pt)Ge were confirmed to be of the TiNiSi-type and the CeCu2-type, respectively. Magnetic, electrical and thermodynamic properties of these materials have been studied in the temperature range 1.5 K T 300 K. CeRhGe orders antiferromagnetically below 9.3 K, whereas in CeIrGe cerium is in an intermediate valence state and no magnetic transition is observed down to 1.5 K. Resistivity and specific heat measurements reveal a magnetic transition near 3.4 K for both CePdGe and CePtGe. According to the present investigations the compounds CeMGe, with M = Rh, Pd, Pt are classified as magnetically ordered Kondo systems.  相似文献   

4.
Magnetic susceptibility, resistivity, and neutron diffraction measurements have been obtained for a series of CrPd alloys containing up to 3 at.% Pd. The Néel temperature variation is irregular for a solute which is to the right of Cr in the periodic table.  相似文献   

5.
We report on the formation and the low-temperature physical properties of a novel compound EuPdGe3 that crystallizes with the tetragonal BaNiSn3-type crystal structure. The material exhibits antiferromagnetic ordering below TN=12.4 K, as inferred from the magnetic susceptibility, heat capacity and electrical resistivity data. The compound shows good metallic conductivity.  相似文献   

6.
陈鹏  Takamura K 《中国物理 B》2008,17(6):2204-2207
This paper reports that 9nm zincblende CrAs is grown by molecular-beam epitaxy on InAs buffer layer. The zb-CrAs shows ferromagnetism at room temperature and the total magnetic moment 3.09 ±0.15μB per CrAs unit. The temperature dependence of zb-CrAs resistance R shows metallic behaviour.  相似文献   

7.
Magnetic and electrical properties of UIrSi3 are described. This silicide, which is the only one of UTSi3 composition (T = transition metal), crystallizes with the BaNiSn3-type structure and orders antiferromagnetically below 42 K. Metamagnetic transitions are observed for fields of ≈ 5.6 and ≈ 3.2 T at 30 and 38 K, respectively.  相似文献   

8.
We present various investigations on the transport, magnetic and thermodynamic properties of the new ternary compounds REPd2Ga3 with RE = Pr, Nd, Sm. While PrPd2Ga3 does not show long-range magnetic order down to about 0.3 K, both NdPd2Ga3 and SmPd2Ga3 order magnetically. The latter exhibits a ferromagnetic ground state with weak ordered moments below T c = 16.9 K and the former orders antiferromagnetically below T N = 6.5 K with ordered Nd moments of 1.99(4) μB at saturation in the basal plane oriented perpendicular to the propagation vector k = [1/2, 0, 0]. The possibility of a Kondo type interaction in PrPd2Ga3 is discussed.  相似文献   

9.
The compound Bi24(CoBi)O40 has been synthesized using the solid-phase reaction method. The temperature and field dependences of the magnetic moment in the temperature range 4 K < T < 300 K and the temperature dependences of the EPR line width and g-factor at temperatures 80 K < T < 300 K have been investigated. The electrical resistivity and thermoelectric power have been measured in the temperature range 100 K < T < 1000 K. The activation energy has been determined and the crossover of the thermoelectric power from the phonon mechanism to the electron mechanism with variations in the temperature has been observed. The thermal expansion coefficient of the samples has been measured in the temperature range 300 K < T < 1000 K and the qualitative agreement with the temperature behavior of the electrical resistivity has been achieved. The electrical and structural properties of the compound have been explained in the framework of the model of the electronic-structure transition with inclusion of the exchange and Coulomb interactions between electrons and the electron-phonon interaction.  相似文献   

10.
We report on properties of layered coherent structures of Pd and Co, prepared by RF sputtering. X-ray diffraction analysis characterizes these films as having a well-ordered periodic structure (periods λ in the range 10A < λ < 80A) of stacked (111) planes of fcc Co and Pd. Room temperature magnetic properties were measured with a vibrating sample magnetometer. All films are ferromagnetic, with a magnetic moment in excess of that attributable to Co. This excess, which increases as λ decreases, is interpreted as induced ferromagnetism in the Pd layers. The in-plane magnetization is harder for smaller values of λ and appears to depend mainly on the thickness of the Co layers. The in-plane electrical resistivity was measured in the range 2K–300K by a four-electrode method. Below 40K, the resistivity is dominated by residual resistivity; above this temperature, its rise is attributed mainly to the resistivities of bulk Pd and Co. The λ-dependence of the resistivity is described by a model of interfacial scattering of electrons. Evidence for the presence of coherency strains at small λ is present in the x-ray data, the magnetization behavior, as well as in the interfacial scattering mechanism deduced from the analysis of the resistivity.  相似文献   

11.
The crystalline structures and galvanomagnetic properties have been studied on Co-Fe films of 80–100% Co. It is found that in single- to multiphase transition region the structure of this alloy system is characterised by the minimum electron number per atom. Moreover, the variations in such magnetic parameters as the anomalous Hall constant and saturation induction do not follow the simple mixing rule, but depend on a crystal structure type of the alloy.  相似文献   

12.
The magnetic properties of (ConPdm)r superstructures on Pd(100) and Pd(111) are evaluated using the fully-relativistic spin-polarized screened Korringa-Kohn-Rostoker method. It is found that only in the case of a Pd(111) substrate such superstructures exhibit perpendicular magnetism, while on a Pd(100) substrate the magnetization is oriented in-plane. Also investigated is the effect of interdiffusion in repeated superstructures. By using the inhomogeneous coherent potential approximation (CPA) for layered systems the effect of ordering into (repeated) superstructures can be described in an ab-initio-like manner. It is found that already small amounts of interdiffusion can be decisive for the actual value of the magnetic anisotropy energy. Received 3 November 1999 and Received in final form 18 January 2000  相似文献   

13.
Magnetic and electrical properties of amorphous Mn-Y, Mn-Zr, and Mn-Nb alloys have been investigated. All these alloys have a temperature-dependent susceptibility which is well fitted by a Curie-Weiss law. This implies the existence of localized magnetic moments associated with the Mn atoms. In addition, amorphous Mn-Y alloys exhibit spin-glass characteristics at low temperature. The experimental results of the electrical resistivity show that the temperature coefficient of resistivity (TCR) of both Mn-Y and Mn-Zr are negative, while Mn-Nb has a positive TCR. On the other hand, the resistivity-temperature curves of Mn-Zr and Mn-Nb have nearly the same tendency but are different from that of Mn-Y.  相似文献   

14.
Magnetisation, specific heat, electrical resistivity, magnetoresistivity and Hall effect were measured for several equiatomic ternary (1-1-1) intermetallic compounds of formula RTX with R = U, Th, Hf and Ti, T a transition metal (Co, Ni, Ru, Rh, Pd, Ir, Pt and Au), and X = Al, Ga, Sn and Sb. These compounds crystallize in three different crystal structures: the cubic MgAgAs-type, and the hexagonal Fe2P- and CaIn2-types. All U-compounds, which we focus upon in this paper, exhibit magnetic moments of about 3μB/U at high temperature and encompass U-U distances from 3.51 to 4.68 Å. For the compounds which the largest U-U distances, Kondo-lattice behaviour was observed. The specific heat coefficient γ shows typical metallic values with some enhancement. Remarkably these compounds have an electrical resistivity up to three orders of magnitude larger than that expected and usually found for U-based intermetallic compounds. The Hf- and Th-based compounds serve as nonmagnetic reference materials, however, they also exhibit anomalously larger resistivities.  相似文献   

15.
Amorphous Zr1?xFex samples were prepared in the composition range 0.2 ? x ? 0.9 either by means of vapour deposition or melt spinning. The electrical resistivity was determined in the range 4.2–300 K. Negative temperature coefficients were observed in the whole concentration range. The extended Ziman theory (diffraction model) was found to be able to explain these results only if the effective valence of the Fe atoms involves not only s electrons but also d electrons. The magnetic properties and the 57Fe Mössbauer effect of the Zr1?xFex alloys were studied in the range 4.2–300 K. The Fe-rich alloys are ferromagnetic. The Fe moment vanishes in alloys of an Fe concentration lower than about 50 at%. In most alloys (x ? 0.8) the Curie temperature is below room temperature and continuously decreases with Zr concentration. By means of Mössbauer spectroscopy and magnetic measurements it is shown that compositional short-range order (CSRO) is present to a higher degree in melt-spun alloys than in vapour-deposited alloys. The effect of sign and magnitude of the heat of solution on CSRO and the magnetic properties is discussed.  相似文献   

16.
We report a comparative study of the magnetic properties of free-standing PdN clusters (2 ≤N ≤21) obtained through two different theoretical approaches that are extensively employed in electronic structure calculations: a semi-empirical Tight-Binding (TB) model and an ab-initio DFT pseudopotential model. Conclusions are drawn about the reliability of the TB model for the investigation of the electronic structure and magnetic properties of such complex 4d Transition Metals (TM) systems and we compare the results with previous systematic DFT calculations and comment on some available experiments in the literature.  相似文献   

17.
Ingots of CuIn5Se8 and CuGa5Se8 were prepared by direct fusion of the stoichiometric mixture of the elements. The analysis of X-ray powder diffraction data showed the presence of one single phase with tetragonal structure for CuGa5Se8 and two phases with hexagonal and tetragonal structure for CuIn5Se8. The lattice parameters a and c were refined by means of the program NBS*AIDS83. The phase transition temperatures were obtained by Differential Thermal Analysis measurements performed on samples sealed in evacuated quartz ampoules. Transmittance measurements were used to determine the absorption coefficient α. The values of Eg were obtained from a plot of (αhν)2 vs. . The electrical resistivity was measured from 10 to 400 K using a four-wire configuration. The activation energies were estimated from the Arrhenius plot of the resistivities.  相似文献   

18.
In/Pd and Pd/In/Pd thin films were prepared by thermal evaporation on the SiO2 substrate in a vacuum. The structural and optical properties of the films were investigated by means of X-ray diffractometry (XRD), Auger electron spectroscopy (AES) and spectroscopic ellipsometry (SE). Auger depth profile studies were performed in order to determine the composition of elements in the Pd-In systems. Interdiffusion of metals was detected at room temperature. Optical properties of Pd-In composite layers formed due to the interdiffusion were derived from ellipsometric quantities Ψ and Δ measured in the photon energy range 0.75-6.50 eV at different angles of incidence. The effective optical spectra show absorption peaks dependent on the composition of nonuniform films. The XRD patterns indicated formation of Pd1−xInx intermetallic phases in the samples.  相似文献   

19.
Spinel compounds with the general formulas ACr2X4 and ACr2−xBxX4 (where A=Cd, Zn, Hg, Ga, Cu; X=S, Se, Te, O; B=Ga, In, Sb), including also substitution of two different cations in the tetrahedral subarray, exhibit different correlations of the magnetic and electrical properties. These properties are correlated with the ionic radii of cations and anions. The solid solutions of the boundary compounds reveal, e.g. correlations of metallic conductivity and a semiconductor–metal phase transition. In some spinel solid solutions the latter phase transition is accompanied by the magnetic phase transitions, i.e. either AF-F or Fi-F. Magnetic and electrical properties and their correlations in different spinel series with chromium are discussed in the frames of the phase diagram of the spinel-type compounds with chromium. Different mechanisms leading to the spin-glass state are discussed and illustrated.  相似文献   

20.
The magnetization, susceptibilityX and specific heatC of epitaxially grown EuS/SrS multilayers measured at low temperatures is reported.C changes with decreasing thickness of the individual EuS and SrS layers, i.e. decreasing modulation length, from the behavior of nearly pure EuS(CT 3/2) to a behavior resembling that of spin-glass samples of EuxSr1–xS (approximatelyC T). For multilayers with increasing thickness ratior =d M/dN (M=EuS,N=SrS),C decreases towards pure EuS, thus showing a transition from spin-glass to ferromagnet. The paramagnetic Curie temperature obtained fromX is reduced with respect to that of pure EuS for layers with small EuS layer thickness. All these effects can be explained by the formation of EuxSr1–xS intrrmediate diffusion layers of a fewnm thickness during the evaporation process. Reduction of the substrate temperature results in a much smaller diffusion layer.Dedicated to Prof. Dr. G. von Minnigerode on the occasion of his 60th birthday  相似文献   

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