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1.
Superconductivity is reported for a new class of ternary compounds of general formula R5T4X10 where R is Sc, Y or a rare earth, T a transition metal of the platinum or iron groups and X either Si or Ge. Critical temperatures up to 8.6 K are observed. The relationship with non-superconducting compounds of similar composition and structure is discussed. 相似文献
2.
First-principles calculations based on density functional theory was performed to analyse the structural stability of transition metal carbides TMC (TM = Ru, Rh, Pd, Os, Ir, Pt). It is observed that zinc-blende phase is the most stable one for these carbides. Pressure-induced structural phase transition from zinc blende to NiAs phase is predicted at the pressures of 248.5 GPa, 127 GPa and 142 GPa for OsC, IrC and PtC, respectively. The electronic structure reveals that RuC exhibits a semiconducting behaviour with an energy gap of 0.7056 eV. The high bulk modulus values of these carbides indicate that these metal carbides are super hard materials. The high B/G value predicts that the carbides are ductile in their most stable phase. 相似文献
3.
Magnetic susceptibility studies on the hexagonal ternary equiatomic RTSn (R = rare earth and Y; T = Pt, Rh) compounds have been realized. These compounds are isostructural to Fe2P with space group P
2m. The ordering temperatures of all compounds are smaller than 19 K. The susceptibility of YTSn is temperature independent. 相似文献
4.
In Y(Fe, M)2 compounds, the presence of Fe moments even at high M concentrations and the appearance of a percolation limit for the onset of long range magnetic order is typical. A dominance of the volume contribution to the isomer shift is obtained, indicating that for the Fe atoms charge transfers are of minor importance. 相似文献
5.
《Journal of magnetism and magnetic materials》1987,67(2):232-238
The crystal structures and the physical properties of U4M7Ge6 (M = Ru, Os) and UM2Ge2 (M = Rh, Ir) have been investigated. The former crystallize in the cubic structure of U4Re7Si6; U4Ru7Ge6 orders ferromagnetically at TC ≈ 10–13 K whereas U4Os7Ge6 remains paramagnetic down to 4.2 K. The latter whise structures derive from the tetragonal ThCr2Si2 or CaBe2Ge2 types display limited homogeneity ranges; URh2Ge2 exhibits a dense-Kondo behaviour at low temperatures; UIr2Ge2 shows polymorphism and its physical properties are strongly influenced by its crystal structure. 相似文献
6.
7.
NMR and NQR studies on two interesting systems (URu2Si2, CeTIn5) were performed under high pressure. (1) URu2Si2: In the pressure range 3.0 to 8.3 kbar, we have observed new 29Si NMR signals arising from the antiferromagnetic (AF) region besides the previously observed 29Si NMR signals which come from the paramagnetic (PM) region in the sample. This gives definite evidence for spatially-inhomogeneous
development of AF ordering below T
0 of 17.5 K. The volume fraction is enhanced by applied pressure, whereas the value of internal field (∼91 mT) remains constant
up to 8.3 kbar. In the AF region, the ordered moment is about one order of magnitude larger than 0.03 μB. (2) CeTIn5: The pressure and temperature (T) dependences of nuclear spin-lattice relaxation rate 1/T
1 of 115In in CeTIn5 have shown that the superconductivity (SC) occurs close to an AF instability. From the T dependences of 1/T
1 and Knight shift below T
c. CeTIn5 has been found to exhibit non-s wave (probable d wave) SC with even parity and line nodes in the SC energy gap. 相似文献
8.
M. Diviš 《Physica B: Condensed Matter》2008,403(1):170-173
First-principles calculations based on density-functional theory were performed for the first time on NpTAl (T=Co, Ni, Rh, Ir and Pt) and NpNiGa. The electronic density of states and equilibrium volume were studied using relativistic full-potential APW plus local-orbitals calculations. The magnetocrystalline anisotropy energy was estimated from total-energy calculations and the a-axis was predicted to be the easy axis of magnetization with the exception of T=Rh. Finally, we employed the LSDA+U method to mimic the orbital polarization and to obtain the correct total magnetic moments in experimental equilibrium. 相似文献
9.
Pressure-induced phase transitions in the ZrXY (X= Si,Ge, Sn;Y= S,Se, Te) family compounds
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Pressure is an effective and clean way to modify the electronic structures of materials, cause structural phase transitions and even induce the emergence of superconductivity. Here, we predicted several new phases of the ZrXY family at high pressures using the crystal structures search method together with first-principle calculations. In particular, the ZrGeS compound undergoes an isosymmetric phase transition from P4/nmm-I to P4/nmm-II at approximately 82 GPa. Electronic band structures show that all the high-pressure phases are metallic. Among these new structures, P4/nmm-II ZrGeS and P4/mmm ZrGeSe can be quenched to ambient pressure with superconducting critical temperatures of approximately 8.1 K and 8.0 K, respectively. Our study provides a way to tune the structure, electronic properties, and superconducting behavior of topological materials through pressure. 相似文献
10.
We investigate the intrinsic spin Hall conductivity (SHC) and the d-orbital Hall conductivity (OHC) in metallic d-electron systems, by focusing on the t2g-orbital tight-binding model for Sr2MO4 (M=Ru, Rh, Mo). The conductivities obtained are one or 2 orders of magnitude larger than predicted values for p-type semiconductors with approximately 5% hole doping. The origin of these giant Hall effects is the "effective Aharonov-Bohm phase" that is induced by the d-atomic angular momentum in connection with the spin-orbit interaction and the interorbital hopping integrals. The huge SHC and OHC generated by this mechanism are expected to be ubiquitous in multiorbital transition metal compounds, which opens the possibility of realizing spintronics as well as "orbitronics" devices. 相似文献
11.
T.I. Ivanova S.A. Nikitin A. Gilewski 《Journal of magnetism and magnetic materials》2010,322(13):1741-1743
Magnetization isotherms for polycrystalline TbMnGe and DyMnGe compounds were measured at the temperature 4.2 K in pulsed magnetic fields (up to 360 kOe). The received isotherms demonstrate the appearance of metamagnetic transitions at low temperatures. Both compounds crystallize in the orthorhombic TiNiSi-type structure. It was found that the magnetic phase transitions with a destruction of ferrimagnetic spiral structure occur in the TbMnGe and DyMnGe compounds in high magnetic fields. An attempt was undertaken to explain the nature of these transitions using the results of the powder neutron diffraction and the qualitative estimation of the exchange interaction values on the basis of the molecular field theory. 相似文献
12.
聂静 《原子与分子物理学报》2017,34(6)
基于密度泛函理论(DFT)的B3LYP方法,计算并确定了M2NO(M=Sc-Zn)的基态结构、电子态和频率。计算结果和已有的相关实验或计算结果基本一致。随着元素周期表从左向右,基态结构M2NO的N-O伸缩振动频率逐渐增大,而N-O键长逐渐减小,NO与M2相互作用削弱了M-M键。 相似文献
13.
T. Asaji 《Applied magnetic resonance》2004,27(1-2):197-205
Successive structural phase transitions of (4-ClC6H4NH3)2CuCl4, which occur in a very narrow temperature range were reinvestigated by Fourier transform nuclear quadrupole resonance (FT NQR) measurements. The phase transitions at 275.5 and 277.0 K were confirmed. The effect of the deuteration of the ammonium end on these transitions was studied. The35Cl NQR frequencies of organic cation were observed to decrease by about 4 kHz and the phase transition temperatures to decrease by about 2 K by the deuteration, suggesting that the ?NH3 + … Cl hydrogen bond is weakened by the deuteration. The magnetic phase transition temperature of 8.6 K showed no remarkable change within experimental error by the deuteration. It was found that the magnetically ordered state is broken by the radio-frequency magnetic field of about 15–35 Oe usually employed in pulsed NQR. However, in the deuterated compound (4-ClC6H4ND3)2CuCl4, the ordered state was found to be stabler for the usual radiofrequency power. By combining with the NQR data of (4-ClC6H4NH3)2CuBr4 and (3,5-Cl2C6H3NH3)2CuCl4, the possibility is discussed of tuning the interlayer interaction between the organic cation layer and the inorganic complex anion layer by the halogen substitution in the organic cation as well as by the halogen replacement in the inorganic complex anion. 相似文献
14.
聂静 《原子与分子物理学报》2016,33(6):1025-1030
基于密度泛函理论(DFT)的B3LYP方法,计算并确定了M_2NO(M=Sc-Zn)的基态结构、电子态和频率.计算结果和已有的相关实验或计算结果基本一致.随着元素周期表从左向右,基态结构M_2NO的N-O伸缩振动频率逐渐增大,而N-O键长逐渐减小,NO与M2相互作用削弱了M-M键. 相似文献
15.
ESR studies in the GdT2Sn2 (T = 3d or 4d transition metals) powdered samples were performed. All investigated compounds are bottlenecked systems. The thermal broadening of the linewidth increases when the number of transition metal d electrons decreases. The Δg shift is equal to zero for T = 3d and is negative for T = 4d metals. 相似文献
16.
Crystal structures,phase relationships,and magnetic phase transitions of R_5M_4 compounds (R = rare earths,M = Si,Ge)
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Our recent studies of the crystal structures, phase transitions, and magnetic properties of intermetallic compounds R5M4 (R = rare earths; M = Si, Ge) are reviewed briefly. First, crystal structures, phase relationships, and magnetic properties of several 5:4 compounds, including Nd5Si4xGex , Pr5Si4xGex, Gd5xLaxGe4,La5Si4, and Gd5Sn4 , are presented. In particular, the canted spin structures as well as the magnetic phase transitions in Pr5Si2Ge2 and Pr 5 Ge 4 investigated by neutron powder diffractions and small-angle neutron scattering are reviewed. Second, the crystal structures and magnetic properties of the most studied compounds Gd5(Si,Ge)4 are summarized. The focus is on the parent compound Gd5Ge4 , which is an amazing material exhibiting magnetic anisotropy, angular dependent spin-flop transition, metastable magnetic response, Griffiths-like phase, thermal effect under pulsed fields, antiferromagnetic and ferromagnetic resonances, pronounced effects of impurities, and high-field induced magnetic transitions. 相似文献
17.
From a temperature dependent ESR study of Mn2+-doped crystals of M(BF4)2·6H2O, M Zn, Co and Ni, new structural phase transitions have been detected and studied. First order structural phase transitions occur in Co(BF4)2·6H2O at T1 ~ 281K, T2~189 K and T3~172K (during cooling), in Zn(BF4)2·6H2O at T1 ~ 286 K and in Ni(BF4)2·6H2O at T1 ~ 301 K. A continuous phase transition occurs in Co(BF4)2·6H2O at Tp ~ 257 K, in Zn(BF4)2·6H2O at Tp ~ 277 K and in Ni(BF4)2·6H2O at Tp ~ 294 K. The ESR spectral characteristics suggest similarities in the structures of these fluoroborate compounds in the phase above T1 with the room temperature structure of Mg(ClO4)2·6H2O. All these compounds are found to have a tendency to crystallise in a triply-twinned pseudo-hexagonal form, although the unit cell above T1 is found to be orthorhombic. The structural changes related to the water octahedron around the metal at T1 were found to be very small and basically the same for these three compounds. Although the unit cell structure of Fe(BF4)2·6H2O above the first order phase transition temperature T1 was found to be similar to that of the other fluoroborate compounds, the structural changes occurring at T1 appeared to be quite different. The low temperature thermal behaviour differs considerably in the Co, Fe and Zn compounds. 相似文献
18.
We study the temperature and field dependence of the magnetic and transport properties of the non-Fermi-liquid (NFL) compound Ce(Ru0.5Rh0.5)2Si2. For fields H less, similar0.1 T the results suggest that the observed NFL behavior is disorder driven. For higher fields, however, magnetic and transport properties are dominated by the coupling of the conduction electrons to critical spin fluctuations. The temperature dependence of the susceptibility as well as the scaling properties of the magnetoresistance are in very good agreement with the predictions of recent dynamical mean-field theories of Kondo alloys close to a spin-glass quantum critical point. 相似文献
19.
I. Yu. Gaidukova Guanghua Gou S. A. Granovskii I. S. Dubenko R. Z. Levitin A. S. Markosyan V. E. Rodimin 《Physics of the Solid State》1999,41(11):1885-1890
The lattice parameters a and c of the tetragonal intermetallic compounds RMn2Ge2 (R=La, Sm, Gd, Nd, Tb, and Y) have been measured by x-ray diffraction in the temperature interval 10–800 K. Anomalies are
observed in the temperature dependence of a and c due to phase transitions from the paramagnetic to the magnetically ordered state in the Mn subsystem, transitions between
various magnetically ordered phases due to a change in the magnitude and sign of the Mn-Mn exchange interaction, and magnetic
transitions caused by ordering of the rare-earth subsystem leading to a rearrangement of the magnetic structure of the Mn
subsystem. It is concluded that, along with the lattice parameter a, the lattice parameter c also has an influence on the Mn-Mn exchange interaction.
Fiz. Tverd. Tela (St. Petersburg) 41, 2053–2058 (November 1999) 相似文献
20.
Silhanek AV Jaime M Harrison N Fanelli VR Batista CD Amitsuka H Nakatsuji S Balicas L Kim KH Fisk Z Sarrao JL Civale L Mydosh JA 《Physical review letters》2006,96(13):136403
We report measurements and analysis of the specific heat and magnetocaloric effect-induced temperature changes at the phase boundary into the single magnetic field-induced phase (phase II) of U(Ru0.96Rh0.04)2Si2, which yield irreversible properties similar to those at the valence transition of Yb(1-x)Y(x)InCu4. To explain these similarities, we propose a bootstrap mechanism by which lattice parameter changes caused by an electric quadrupolar order parameter within phase II become coupled to the 5f-electron hybridization, giving rise to a valence change at the transition. 相似文献