共查询到20条相似文献,搜索用时 15 毫秒
1.
V. K. Voronkova R. T. Galeev S. Shova G. Novitchi C. I. Turta A. Caneschi D. Gatteschi J. Lipkowski Yu. A. Simonov 《Applied magnetic resonance》2003,25(2):227-247
New compounds, [Cu3Ln2(ClCH2COO)12(H2O)8]·2H2O with Ln = Nd3+ (I), Sm3+ (II), Pr3+ (III), built up of pentanuclear clusters were synthesized and studied by means of X-ray analysis and electron paramagnetic
resonance (EPR). X-ray data show that all compounds are isostructural and the pentanuclear clusteres may be considered as
a linear system with alternating Cu(II) and Ln(III) ions: Cu(2)-L1-Ln-L2-Cu(1)-L2-Ln-L2-Cu(2) with L1 and L2 being bridging fragments and Cu(1) and Cu(2) being structurally nonequivalent copper complexes. EPR studies demonstrate that
in the temperature range of 100–293 K the signals due to only one type of the copper complexes are observed in the spectra
of I–III. AtT<100 K the spectral temperature dependence is nontrivial. AtT<30 K new signals are detected in the spectra of I and II. The temperature dependence of the EPR spectra is interpreted under
the assumption that the parameter of the exchange interaction Cu(2)-Ln considerably exceeds the parameter of the interaction
Cu(1)-Ln. EPR spectra are calculated for the fragments of five paramagnetic centers in the frames of the model taking into
account the nonequivalence of two copper complexes, short longitudinal and transverse paramagnetic relaxation times of the
rare-earth ions at room temperature and the change of the relaxation rates when the temperature decreases. The results of
the calculations show that it is possible to obtain information about the interactions in the system on the basis of the analysis
of the temperature dependence of the EPR spectra of the central copper complex. The parameter of the isotropic part of the
exchange interaction between copper and neodymium ions (for the interaction Cu(2)-Nd) is estimated as about 15 cm−1. A considerable rearrangement of the spin states when the temperature changes is found for all complexes. 相似文献
2.
E. I. Yurieva O. G. Reznitskikh V. G. Bamburov 《Bulletin of the Russian Academy of Sciences: Physics》2009,73(7):1010-1012
The electronic structure and Ln-O (Ln = La, Ce, Pr, Nd, Pm, Sm, Eu) bonding parameters have been calculated by the X
α method of discrete variation taking into account the real structure of LaNb7O12 oxoniobate. It is shown that the experimentally observed tendencies in the change in the oxoniobate stability correlate with
the decrease in the average electron-proton binding energy of LnO8 clusters and enhanced repulsion between Ln and O orbitals to the end of the lanthanide series.
Original Russian Text ? E.I. Yurieva, O.G. Reznitskikh, V.G. Bamburov, 2009, published in Izvestiya Rossiiskoi Akademii Nauk.
Seriya Fizicheskaya, 2009, Vol. 73, No. 7, pp. 1066–1068. 相似文献
3.
The magnetic properties of La2−2x
Sr1+2x
Mn2O7 polycrystals (x=0.3–0.4) are studied over a broad temperature range 80–600 K. Quasi-two-dimensional manganites have a complex magnetic structure
that undergoes several transitions from one type of magnetic ordering to another. A specific feature of these manganites is
a hyperbolic dependence of inverse susceptibility in the transition region from the magnetically ordered to paramagnetic state
for T>360 K. This suggests the onset of ferrimagnetism. Electron irradiation to a fluence Φ=1×1018 electrons/cm2 is shown to have no effect on the long-range magnetic order while favoring the formation of paramagnetic polarons and of
an inhomogeneous paramagnetic state.
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Translated from Fizika Tverdogo Tela, Vol. 45, No. 8, 2003, pp. 1440–1445.
Original Russian Text Copyright ? 2003 by Arbuzova, Naumov, Arbuzov. 相似文献
4.
Haiying Chen Yan ZhangJingzhi Han Honglin DuChangsheng Wang Yingchang Yang 《Journal of magnetism and magnetic materials》2008
A series of R2Fe17 (R=Sm, Gd, Tb, Dy, Er) have been synthesized. The magnetocaloric effect (MCE) of these compounds has been investigated by means of magnetic measurements in the vicinity of their Curie temperature. The Curie temperature of Er2Fe17 is 294 K. The maximum magnetic entropy change of Er2Fe17 under 5 T magnetic field is ∼3.68 J/kg K. In the R2Fe17 (R=Sm, Gd, Tb, Dy, Er) system, the maximum magnetic entropy change under 1.5 T magnetic field is 1.72, 0.89, 1.32, 1.59, 1.68 J/kg K corresponding to their Curie temperature (400, 472, 415, 364, 294 K), respectively. 相似文献
5.
The magnetic properties of Y2
B
2/3Mo4/3O7 complex oxides (B = Co, Fe) were studied in the temperature range 2–300 K. At low temperatures, these compounds exhibit spin-glass properties
with freezing temperatures T
f=26 and 33 K, respectively, and typical features in the magnetic hysteresis and in the dependences of the real part of the
dynamic magnetic susceptibility on temperature and ac magnetic field frequency. Above T
f, the static magnetic susceptibility of the samples studied depends on the applied magnetic field, which is tentatively assigned
to the presence of metallic cobalt and/or yttrium orthoferrite YFeO3 introduced in the course of sample preparation.
__________
Translated from Fizika Tverdogo Tela, Vol. 47, No. 12, 2005, pp. 2182–2188.
Original Russian Text Copyright ? 2005 by Bazuev, Korolev. 相似文献
6.
Crystal and magnetic structure of the Sm0.55Sr0.45MnO3 and (Nd0.545Tb0.455)0.55Sr0.45MnO3 manganites
A. I. Kurbakov V. A. Trounov A. M. Balagurov V. Yu. Pomyakushin D. V. Sheptyakov O. Yu. Gorbenko A. R. Kaul 《Physics of the Solid State》2004,46(9):1704-1710
Neutron diffraction data are presented for the 152Sm0.55Sr0.45MnO3 (SSM) and (Nd0.545Tb0.455)0.55Sr0.45MnO3 (NTSM) manganites. The Nd and Tb contents in the latter composition are such that the average radius of the A cation 〈r
A
〉 in these two compounds is the same. The difference in local tolerance factor fluctuations was about 10%. It was found that
replacement of a rare-earth cation with leaving 〈r
A
〉 unchanged has practically no effect on the structural and transport properties; indeed, both compounds are metals at low
temperatures, have the same crystal structure from liquid-helium to room temperature, and exhibit the same pattern of structural
distortions at the onset of magnetic ordering. Magnetic moments of Mn ions in both compositions are ferromagnetically ordered
at low temperatures, with T
C
=122 and 90 K for the SSM and NTSM, respectively. Below 80 K, the rare-earth cation moments in NTSM undergo additional ordering.
In contrast to compositions that are close in Sr concentration (x
Sr=0.4, 0.5), which feature a phase-separated state with a mixture of the ferromagnetic metallic and antiferromagnetic insulator
phases, the ground state of both studied compositions with x
Sr=0.45 is uniformly ferromagnetic and metallic.
__________
Translated from Fizika Tverdogo Tela, Vol. 46, No. 9, 2004, pp. 1650–1656.
Original Russian Text Copyright ? 2004 by Kurbakov, Trounov, Balagurov, Pomyakushin, Sheptyakov, Gorbenko, Kaul. 相似文献
7.
Magnetic properties and structural chemistry of ternary silicides (RE,Th, U)Ru2Si2 (RE = RARE EARTH)
K. Hiebl C. Horvath P. Rogl M.J. Sienko 《Journal of magnetism and magnetic materials》1983,37(3):287-296
Ternary silicides (RE, Th, U)Ru2Si2 have been synthesized from the elements. All the compounds (RE = Y, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) were found to be isotypic and to crystallize with the structure type of ThCr2Si2 (ordered derivative of the BaAl4-type). The magnetic behavior of these alloys was studied in the temperature range 1.5 K < T < 1100 K. Magnetic susceptibilities at temperatures T > 300 K closely follow a typical Van Vleck paramagnetism of free RE3+-ions. In the case of CeRu2Si2 susceptibilities are well described for 20 K < T < 1100 K by a Van Vleck paramagnetism of widely spaced multiplets; the observed effective paramagnetic moment μeff = 2.12 BM indicates a high percentage (85%) of Ce3+. SmRu2Si2 yields an effective moment μeff = 0.54 BM, which compares reasonably well with the Hund's rule J = 5/2 ground level for free Sm+ and a low-lying excited level with J = 7/2. For temperatures T > 15 K the magnetic susceptibility as a function of temperature follows the “Van Vleck behavior” for free Sm3+. At low temperatures ferromagnetic ordering was encountered for (Pr, Nd, Ho, Er, Tm)Ru2Si2, whereas antiferromagnetic ordering was observed for (Sm, Gd, Tb, Dy)Ru2Si2. The ordering temperatures are generally below 55 K. No superconductivity was found for temperatures as low as 1.8 K. 相似文献
8.
V. V. Lemanov A. V. Sotnikov E. P. Smirnova M. Weihnacht 《Physics of the Solid State》2002,44(11):2039-2049
Ceramic samples of (1−x)SrTiO3-xSrMg1/3Nb2/3O3 and (1−x)SrTiO3-xSrSc1/2Ta1/2O3 were prepared, and their dielectric properties were studied at x=0.005–0.15 and 0.01–0.1, respectively, at frequencies 10 Hz–1 MHz and at temperatures 4.2–350 K. A giant dielectric relaxation
was observed in the temperature range 150–300 K, and not so strong but well-developed relaxation was found in the temperature
range 20–90 K. The activation energy U and the relaxation time τ0 were determined to be 0.21–0.3 eV and from 10−11 to 10−12 s for the high-temperature relaxation and 0.01–0.02 eV and 10−8–10−10 s for the low-temperature relaxation, respectively. The additional local charge compensation of the heterovalent impurities
Mg2+ and Nb5+ (or Sc3+ and Ta5+) by free charge carriers or the host ion vacancies is suggested to be the underlying physical mechanism of the relaxation
phenomena. On the basis of this mechanism, the Maxwell-Wagner model and the model of reorienting dipole centers Mg2+ (or Sc3+) associated with the oxygen vacancy are proposed to explain the high-temperature relaxation with some arguments in favor
of the latter model. The polaron-like model with the Nb5+-Ti3+ center is suggested as the origin of the low-temperature relaxation. The reasons for the absence of ferroelectric phase transitions
in the solid solutions under study are also discussed.
From Fizika Tverdogo Tela, Vol. 44, No. 11, 2002, pp. 1948–1957.
Original English Text Copyright ? 2002 by Lemanov, Sotnikov, Smirnova, Weihnacht.
This article was submitted by the authors in English. 相似文献
9.
The phenomenon of giant intrinsic magnetic hardness is investigated in compounds R1−x
Sm
x
Co2Ni3 with R=Y, Pr, Gd, Tb, Er. Partial Er substitution for Sm actually increases magnetic hardness while all other substitutions
decrease magnetic hardness. The strength of coercivity is thus dependent on both the sign and magnitude of the crystal field
interaction. The temperature dependence of coercivity is complex in the case of Pr substitution as a result of competing effects
from thermal activation and a decrease in anisotropy at low temperatures.
This study has been supported by a grant from the National Science Foundation. 相似文献
10.
A. I. Klyndyuk 《Physics of the Solid State》2009,51(2):270-274
The electrical resistivity ρ and the thermopower S of ceramic materials LnBaCuFeO5 + δ (Ln= La, Pr, Nd, Sm, Gd-Lu) are measured in air at temperatures in the range from 300 to 1100 K. All the studied ferrocuprates
are p-type semiconductors. The electrical resistivity ρ and the thermopower S of these compounds increase with a decrease in the radius of the Ln
3+ cation (with an increase in the number of 4f electrons n in Ln
3+). The nonmonotonic behavior of the dependences ρ=f(n) and S=f(n) indicates that the electrical properties of the layered ferrocuprates LnBaCuFeO5 + δ depend on the electronic configuration of the Ln
3+ cation. The power factors P calculated for the LnBaCuFeO5 + δ ceramic materials from the experimental values of ρ and S increase with increasing temperature and, at T = 1000 K, reach the maximum values P = 102.0 and 54.1 μW m−1 K−2 for Ln = Pr(4f
2) and Sm(4f
5), respectively, and become close to each other and equal to 30–35 μW m−1 K−2 for Ln = Gd(4f
7), Dy(4f
9), and Ho(4f
10). 相似文献
11.
N. S. Uporova S. A. Uporov V. E. Sidorov 《Journal of Experimental and Theoretical Physics》2012,114(2):281-287
The magnetic susceptibility of metallic samarium and the Al2Sm intermetallic compound has been experimentally studied by the Faraday method in the temperature range of 300–1800 K. It
has been shown that the temperature dependences of the magnetic susceptibility of Sm and Al2Sm in a crystalline state can be described in the framework of Van Vleck paramagnetism theory taking into account variable
valence and the contribution from the conduction electrons. Using this theoretical interpretation of the data, the effective
valence of samarium in the metallic state and in the Al2Sm intermetallic compound has been estimated as a function of the temperature. 相似文献
12.
R. B. Morgunov E. V. Kurganova T. G. Prokhorova é. B. Yagubski S. V. Simonov R. P. Shibaeva 《Physics of the Solid State》2008,50(4):684-690
Layered single crystals of the (BEDO-TTF)6[M(CN)6](H3O,CH3CN)2 (M = Fe, Cr) compounds with alternating conducting layers of BEDO-TTF and [M(CN)6](H3O,CH3CN)2 are studied. The contributions to the magnetic susceptibility from charge carriers in BEDO-TTF layers and from the subsystem of localized magnetic moments of iron (or chromium) transition metal complexes are separated
for both compounds under investigation. It is revealed that the crystals with [Fe(CN))6]3− anions at a temperature of ∼80 K and the crystals with [Cr(CN))6]3− anions at ∼30 K undergo magnetic transitions which are accompanied by drastic changes in the parameters of the EPR lines
associated with the BEDO-TTF layers and the subsystem of localized spins of transition metal complexes. It is established that the presence of the BEDO-TTF layers in the structure affects the magnetic properties of iron and chromium hexacyanide complexes.
Original Russian Text ? R.B. Morgunov, E.V. Kurganova, T.G. Prokhorova, E.B. Yagubskiĭ, S.V. Simonov, R.P. Shibaeva, 2008,
published in Fizika Tverdogo Tela, 2008, Vol. 50, No. 4, pp. 657–663. 相似文献
13.
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
14.
New ternary silicides (RE,Th,U) Os2Si2 have been synthesized from the elements. All the compounds (RE= Y,La,Ce,Pr,Nd,Sm,Gd,Tb,Dy,Ho,Er,Tm,Yb, Lu) were found to be isotypic and to crystallize with the ordered BaAl4-type of structure (ThCr2Si2-type). Magnetic properties of these alloys — studied in the temperature range 1.5<T<1100 K — reveal a typical Van Vleck paramagnetism of free RE3+ ions at temperatures higher than 300 K. The observed effective paramagnetic moment of CeOs2Si2, μ(eff)=0.98 BM, is compatible with a rather low concentration (15%) of Ce3+. The effective moment of SmOs2Si2, μ(eff)=0.47 BM, is in reasonable agreement with a Hund's rule ground level for free Sm3+. For temperatures above 25 K, the magnetic susceptibility as a function of temperature corresponds to the Van Vleck behavior for free Sm3+ (closely spaced multiplet, ,. Magnetic ordering temperatures of REOs2Si2 silicides are generally below 42 K. (Pr,Nd,Ho,Er,Tm) Os2Si2 exhibit ferromagnetic ordering whereas (Sm,Gd, Tb,Dy) Os2Si2 show antiferromagnetic behavior. Above 1.8 K none of the samples was found to be superconducting. 相似文献
15.
P. de la Presa M. Forker J.Th. Cavalcante A.P. Ayala 《Journal of magnetism and magnetic materials》2006
Perturbed angular correlation spectroscopy has been used to investigate the combined magnetic and electric hyperfine interaction of the probe nucleus 111Cd in ferromagnetically ordered rare earth (R)-dialuminides RAl2 as a function of temperature for the rare earth constituents R=Pr, Nd, Sm, Eu, Tb, Dy, Ho and Er. In compounds with two magnetically non-equivalent Al sites (R=Sm, Tb, Ho, Er), the magnetic hyperfine field was found to be strongly anisotropic. This anisotropy is much greater than the anisotropic dipolar fields, suggesting a contribution of the anisotropic 4f-electron density to magnetic hyperfine field at the closed-shell probe nucleus. The spin dependence of the magnetic hyperfine field reflects a decrease of the effective exchange parameter of the indirect coupling with increasing R atomic number. For the compounds with the R constituents R=Pr, Nd, Tb, Dy and Ho the parameters B4, B6 of the interaction of the crystal field interaction have been determined from the temperature dependence of the magnetic hyperfine field. The 111Cd PAC spectrum of EuAl2 at 9 K confirms the antiferromagnetic structure of this compound. 相似文献
16.
R. M. Vlasova N. V. Drichko B. V. Petrov V. N. Semkin E. I. Zhilyaeva R. N. Lyubovskaya I. Olejniczak A. Kobayashi H. Kobayashi 《Physics of the Solid State》2004,46(11):1985-1993
Polarized reflectance and optical conductivity spectra of single crystals of two new isostructural organic conductors based
on the BEDT-TSeF molecule, namely, the κ-(BETS)4Hg2.84Br8 superconductor (T
c
=2 K) and the κ-(BETS)4Hg3Cl8 metal, which undergoes a smooth transition to the dielectric state near 35 K, have been obtained in the spectral region 700–6500
cm−1 at temperatures of 300–15 K. At 300 K, the spectra of both compounds are nearly identical and differ from the Drude spectrum
characteristic of metals. The nature of the observed difference is discussed, and the spectra are described in terms of a
cluster approach with inclusion of electron-electron correlations in the Hubbard approximation combined with the Drude model.
The parameters of the theory were determined, including the electron transfer integrals between molecules in a cluster. The
spectra in the conducting plane of the crystals were found to be essentially anisotropic, which should be assigned to specific
features of in-plane interaction between molecules. The spectra of the superconductor and the metal become increasingly different
as the temperature is lowered. The spectra of the metal obtained for T<150 K exhibit splitting of the broad electronic maximum in the mid-IR region into two bands, which is accompanied by a splitting
of a vibronic feature deriving from electron interaction with intramolecular BETS vibrations of ν3(A
g
) symmetry. No such splitting is observed in the superconductor spectra with decreasing temperature.
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Translated from Fizika Tverdogo Tela, Vol. 46, No. 11, 2004, pp. 1921–1929.
Original Russian Text Copyright ? 2004 by Vlasova, Drichko, Petrov, Semkin, Zhilyaeva, Lyubovskaya, Olejniczak, A. Kobayashi,
H. Kobayashi. 相似文献
17.
J.D. Gordon G. Gorodetsky R.M. Hornreich 《Journal of magnetism and magnetic materials》1976,3(4):288-294
The spontaneous magnetization and principal magnetic susceptibilities of TbFeO3 were measured from 4.2 to 300 K. The weak ferromagnetic moment is along the c crystallographic axis in the entire temperature range. The field dependence of the magnetization at 4.2 K was also studied. The magnetic behavior is interpreted in terms of an interaction between the ordered Fe3+ spin system and the electrons occupying the lowest lying “accidental” doublet of the Tb3+ ions. The FeTb interaction and the Tb3+ Van Vl eck susceptibility along the c axis play significant roles in determining the magnetic configuration of the Fe3+ spin system. No indication was found that the TbTb interaction plays a significant role in the magnetic behavior of TbFeO3 at temperature above 4.2 K. 相似文献
18.
The magnetic susceptibility of Al2REM (REM = Gd, Dy, and Ho) intermetallic compounds is experimentally investigated by the Faraday method in a wide temperature
interval (290–2000 K) in different magnetic fields (0.3–1.3 T). In the crystalline state, the temperature dependences of the
susceptibility follow the generalized Curie–Weiss law. In the liquid phase, the magnetic susceptibility of these intermetallic
compounds above the melting point increases for all examined samples. The parameters of the electronic structure of the compounds
are calculated based on the experimental data. It is established that the effective magnetic moment per rareearth metal atom
is smaller than that characteristic of the free REM+ ion. 相似文献
19.
The magnetic susceptibility of some rare earth-indium compounds has been measured in the temperature range 4.2–300 K under a constant field of 1 kOe. The compounds with R = Gd, Tb and Dy are antiferromagnetic, having Néel temperatures between 4.2 and 78 K ; those with R = Ho, Er and Tm seem to be ferromagnetic with ordering temperatures probably below 4.2 K. Y5In3 presents a temperature independent susceptibility. 相似文献
20.
We have studied the low field susceptibility of TPb3 compounds (T = Pr, Nd, Sm, Tb, Dy, Ho) between 3 and 300 K. All these compounds except SmPb3 follow a Curie-Weiss law with a paramagnetic moment close to the free ion value. The compounds with Sm, Tb, Dy and Ho order antiferromagnetically.The magnetization of the three last compounds has been studied in static magnetic fields up to 85 koe. 相似文献