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1.
《Journal of Physics and Chemistry of Solids》2002,63(6-8):969-973
Magnetic susceptibility (χ) and 51V NMR have been measured in (V1−xTix)2O3 near the phase boundary of the metal–insulator transition. It is established that the transition from antiferromagnetic insulating (AFI) to antiferromagnetic metallic phases near xc≈0.05 is not quantum critical, but is discontinuous with a jump of the transition temperature. In the AFI phase at 4.2 K, we observed the satellite in the zero-field 51V NMR spectrum around 181 MHz in addition to the ‘host’ resonance around 203 MHz. The satellite is also observable in the paramagnetic metallic phase of the x=0.055 sample. We associated the satellite with the V sites near Ti, which are in the V3+-like oxidation state, but has different temperature dependence of the NMR shift from that of the host V site. The host d-spin susceptibility for x=0.055 decreases below ∼60 K, but remains finite in the low-temperature limit. 相似文献
2.
A. Campana R. Cantelli F. Cordero M. Corti A. Rigamonti 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,18(1):49-54
Anelastic relaxation and 139LaNQR relaxation rates in La2–xSrxCuO4 for Sr content around 2 and 3 percent are discussed in terms of spin and lattice excitations and of the related ordering
processes. It is argued how the phase diagram of La2–xSrxCuO4 at the boundary between the antiferromagnetic (AF) and the spin-glass phase (x
= 0.02) could be more complicate than previously thought, with a transition to a quasi-long range ordered state at K, as indicated by neutron scattering data. On the other hand, the 139LaNQR spectra are compatible with a transition to an AF phase around K, in agreement with the phase diagram commonly accepted in literature. In this case the peaks in NQR and anelastic relaxation
rates around 150 K and 80 K respectively in La1.98Sr0.02CuO4, yield the first evidence of freezing process involving simultaneously lattice and spin excitations, possibly corresponding
to motion of charged stripes.
Received 18 May 2000 and Received in final form 11 July 2000 相似文献
3.
4.
A. M. Kadomtseva Yu. F. Popov G. P. Vorob’ev K. I. Kamilov A. A. Mukhin V. Yu. Ivanov A. M. Balbashov 《Physics of the Solid State》2006,48(11):2134-2136
The magnetic and magnetoelastic properties of single crystals of electron-doped rare-earth manganites La1?x Sr x MnO3 are studied. Phase transitions from the A-type antiferromagnetic phase to the C-type anti-ferromagnetic phase in a strong magnetic field are revealed in La1?x Sr x MnO3 manganites with a strontium content x = 0.65. A similar phase transition is observed in manganites with a strontium content x = 0.8, at which the La0.2Sr0.8MnO3 manganite is assumed to transform from the C-type antiferromagnetic phase to the G-type antiferromagnetic phase. 相似文献
5.
La1-χxSrχCuO2:5 is composed of coupled cuprate ladders, and admits hole doping without structural alteration. It is thus a candidate novel superconductor, although to date superconductivity has not been found. Here we study the undoped, parent state to elucidate the interplay between spin liquid and antiferromagnetic ground states in systems with potential for superconductivity 相似文献
6.
The magnetic phase transition and magnetocaloric effects in Fe-doped MnNiGe alloys are investigated. The substitution of Fe for Ni decreases the structural transition temperature remarkably, resulting in the magnetostructural transition occurring between antiferromagnetic and ferromagnetic states in MnNi1 - xFexGe alloy. Owing to the enhanced ferromagnetic coupling induced by the substitution of Fe, metamagnetic behaviour is also observed in TiNiSi-type phase of MnNi1 - xFexGe alloys at temperature below the structural transition temperature. 相似文献
7.
Magnetic properties of the CoxNi1?xMnGe system have been studied by magnetometric measurements. It was shown that the solid solutions exist for 0 ? χ ? 1, with the crystal structure of NiTiSi type. The samples with the low Co concentrations (0 ? χ ? 0.2) have antiferromagnetic properties. At higher concentrations (0.3 ? χ ? 0.5) the samples exhibit a more complex behaviour, at low temperatures having antiferromagnetic properties. At growing temperatures the change of the magnetic ordering is observed. The samples with large Co concentration (0.6 ? χ ? 1.0) are ferromagnets. 相似文献
8.
J. H. de Araújo J. B. M. da Cunha A. Vasquez L. Amaral J. T. Moro F. C. Montenegro S. M. Rezende M. D. Coutinho Filho 《Hyperfine Interactions》1991,67(1-4):507-511
57Fe Mössbauer effect measurements in the diluted Ising antiferromagnet Fe x Zn1?x F2 withx=0.25 andx=0.57 at temperatures between 4.2 and 55 K, are reported. DC suceptibility measurements show a spin-glass (SG) phase at low temperatures forx≤0.31. Our Mössbauer spectra show a phase transition to a SG state with antiferromagnetic order (AFSG) forx=0.25 and only antiferromagnetic order forx=0.57. 相似文献
9.
M. Hinczewski A. N. Berker 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,51(4):461-472
The anisotropic d=3 tJ model is studied by
renormalization-group theory, yielding the evolution of the system
as interplane coupling is varied from the isotropic
three-dimensional to quasi-two-dimensional regimes.
Finite-temperature phase diagrams, chemical potential shifts, and
in-plane and interplane kinetic energies and antiferromagnetic
correlations are calculated for the entire range of electron
densities. We find that the novel τ phase, seen in earlier
studies of the isotropic d=3 tJ model, persists even for
strong anisotropy. While the τ phase appears at low
temperatures at 30–35% hole doping away from 〈
ni〉=1, at smaller hole dopings we see a complex lamellar
structure of antiferromagnetic and disordered regions, with a
suppressed chemical potential shift, a possible marker of
incommensurate ordering in the form of microscopic stripes. An
investigation of the renormalization-group flows for the isotropic
two-dimensional tJ model also shows a clear pre-signature of the
τ phase, which in fact appears with finite transition
temperatures upon addition of the smallest interplane coupling. 相似文献
10.
A. Sundaresan J.L. Tholence A. Maignan C. Martin M. Hervieu B. Raveau E. Suard 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,14(3):431-438
Neutron and electron diffraction, electrical transport and magnetic measurements have been carried out on a newly synthesized
electron doped Sr1-xCe
x
MnO3 (x = 0.1, 0.2, 0.3 and 0.4) system. For x=0.1, while cooling, it undergoes a first-order metal-insulator transition at 315 K which is associated with a structural
transition from cubic (Pm3m) to tetragonal (I4/mcm) due to Jahn-Teller ordering () which stabilizes a chain like (C-type) antiferromagnetic ground state with . The antiferromagnetic insulator state is insensitive to an applied magnetic field of 7 T. With increase of x, while the nuclear structure at room temperature for x=0.2 and 0.3 remains tetragonal, for x=0.4 it becomes orthorhombic (Imma) where the doping electrons seem to occupy mainly the d
x2-y2 symmetry. Further, the JT distortion and the antiferromagnetic interactions decrease with doping and a small negative magnetoresistance
appears for . Magnetic measurements show that the dilution of antiferromagnetic interaction results into a spin glass like behaviour at
low temperature for the samples with x=0.3 and 0.4. This behaviour is in contrast with the CMR properties of calcium based electron doped systems and hole doped
manganites. The stability of C-type antiferromagnetic ordering in the electron doped system with large A-site cationic size
may be responsible for the absence of double exchange ferromagnetism and CMR effect.
Received 10 September 1999 相似文献
11.
In the frame of a single coherent picture for the electron lattice interactions in mixed valent Rare Earth compounds, the phase diagrams and phonon dispersions are studied. Our model is introduced on a microscopic level and discussed in detail. The mechanism of the phase transition and the role of the lattice is illuminated and various properties are considered in a model calculation. Anomalies in the phonon dispersions of Sm1–x
Y
x
S, which have recently been found, find a satisfying explanation. 相似文献
12.
N. E. Sluchanko A. N. Azarevich A. V. Bogach V. V. Glushkov S. V. Demishev A. V. Levchenko V. B. Filippov N. Yu. Shitsevalova 《Journal of Experimental and Theoretical Physics》2013,116(5):866-871
The transverse magnetoresistance Δρ/ρ(H, T) of Tm1 ? x Yb x B12 single crystals is studied in the ytterbium concentration range corresponding to the antiferromagnet-paramagnet transition in a magnetic field up to 80 kOe at low temperatures. A magnetic H-T phase diagram is constructed for the antiferromagnetic state of substitutional Tm1 ? x Yb x B12 solid solutions with x ≤ 0.1. The contributions to the magnetoresistance in the antiferromagnetic and paramagnetic phases of the dodecaborides under study are separated. Along with negative quadratic magnetoresistance -Δρ/ρ ∝ H 2, the magnetically ordered phase of these compounds is found to have component Δρ/ρ ∝ H that linearly changes in a magnetic field. The negative contribution to the magnetoresistance of Tm1 ? x Yb x B12 is analyzed in terms of the Yosida model for a local magnetic susceptibility. 相似文献
13.
14.
We study the electronic and magnetic properties of ordered perovskites Sr
2FeMO6 (where M is a transition metal), among which
some compounds, like Sr2FeMoO6 are half-metallic
with high Curie temperature while Sr2FeWO6 is an
antiferromagnetic insulator. Using a double exchange type model with an
interaction between localized spins and conduction electrons together with a
tight-binding Hamiltonian and the renormalized perturbation expansion
method, we study the behavior of Tc as a function of the number of
conduction electrons and also as a function of the Fe-M energy difference.
We also consider the Sr2FeMoxW1-xO6
compounds which present a magnetic and metal-insulator transition as a
function of doping. 相似文献
15.
D.M. Raj KumarM. Manivel Raja K. PrabaharV. Chandrasekaran Asok PoddarR. Ranganathan K.G. Suresh 《Journal of magnetism and magnetic materials》2011,323(13):1750-1754
The effect of Si/Ge ratio on resistivity and thermopower behavior has been investigated in the magnetocaloric ferromagnetic Gd5SixGe4−x compounds with x=1.7-2.3. Microstructural studies reveal the presence of Gd5(Si,Ge)4-matrix phase (5:4-type) along with traces of secondary phases (5:5 or 5:3-type). The x=1.7 and 2.0 samples display the presence of a first order structural transition from orthorhombic to monoclinic phase followed by a magnetic transition of the monoclinic phase. The alloys with x=2.2 and 2.3 display only magnetic transitions of the orthorhombic phase. A low temperature feature apparent in the AC susceptibility and resistivity data below 100 K reflects an antiferromagnetic transition of secondary phase(s) present in these compounds. The resistivity behavior study correlates with microstructural studies. A large change in thermopower of −8 μV/K was obtained at the magneto-structural transition for the x=2 compound. 相似文献
16.
I. O. Troyanchuk 《Physics of the Solid State》2006,48(5):898-903
This paper reports on the results of x-ray diffraction and magnetic studies of manganites in the Nd0.9MnOx system with an oxygen content varying in the range 2.84 < x < 2.93. A sample with an oxygen content x = 2.84 undergoes a first-order phase transition at a temperature close to T = 1050 K, whereas an anomaly observed in the elastic properties for a sample with x = 2.93 indicates a phase transition near T ≈ 500 K. It is assumed that these transitions are governed by cooperative ordering of Mn e g orbitals of the same type as in stoichiometric NdMnO3. The manganite at an oxygen content x = 2.85 is an antiferromagnet with a Néel temperature T N = 85 K, whereas the magnetic properties of the manganites at x = 2.90 and 2.93 suggest that an antiferromagnetic component coexists with a ferromagnetic component. The magnetic interaction between the ferromagnetic and antiferromagnetic components manifests itself in the fact that the magnetic moment becomes opposite in direction to the external magnetic field. The properties of the samples are consistent with the hypothesis that part of the neodymium ions (up to 5%) can be substituted for manganese ions. 相似文献
17.
Low field interband Faraday rotation and a.c. magnetic susceptibility are investigated in Hg1?kMnkTe and Hg1?k?xMnkTe semimagnetic semiconductors (k?0.5). The spin glass phase transition is experimentally manifested by characteristic cusps in χ(T) and kinks in θ(T). The transition temperatures obtained from both types of experiments are well correlated which enable us to determine the phase diagram for Hg1?kMnkTe system. The spin glass phase transition occurs at low temperature in quaternary alloys than in Hg1?kMnkTe alloys with identical Mn composition. This implies that the antiferromagnetic interaction between Mn2+ ions due to the virtual valence to conduction band transitions plays a significant role in the mechanism responsible for the spin glass formation. 相似文献
18.
《Journal of magnetism and magnetic materials》2004,279(1):91-102
We present results of an electron paramagnetic resonance (EPR) study of Nd1−xSrxMnO3 with x=0.5 across the paramagnetic to ferromagnetic, insulator to metal transition at 260 K (Tc) and the antiferromagnetic, charge ordering transition (TN=Tco) at 150 K. The results are compared with those on Nd0.45Sr0.55MnO3 which undergoes a transition to a homogeneous A-type antiferromagnetic phase at TN=230 K and on La0.77Ca0.23MnO3 which undergoes a transition to coexisting ferromagnetic metallic and ferromagnetic insulating phases. For x=0.5, the EPR signals below Tc consist of two Lorentzian components attributable to the coexistence of two phases. From the analysis of the temperature dependence of the resonant fields and intensities, we conclude that in the mixed phase ferromagnetic and A-type antiferromagnetic (AFM) phases coexist. The x=0.55 compound shows a single Lorentzian throughout the temperature range. The signal persists for a few degrees below TN. The behaviour of the A-type AFM phase is contrasted with that of the two ferromagnetic phases present in La0.77Ca0.23MnO3. The comparison of behaviour of A-type AFM signal observed in both Nd0.5Sr0.5MnO3 and Nd0.45Sr0.55MnO3 with the two FM phases of La0.77Ca0.23MnO3, vis-à-vis the shift of resonances with respect to the paramagnetic phases and the behaviour of EPR intensity as a function of temperature conclusively prove that the Nd0.5Sr0.5MnO3 undergoes phase separation into A-type AFM and FM phases. 相似文献
19.
Zurab Guguchia Hugo Keller Annette Bussmann-Holder Jürgen Köhler Reinhard K. Kremer 《The European Physical Journal B - Condensed Matter and Complex Systems》2013,86(10):1-4
Specific heat and magnetization measurements demonstrate that the antiferromagnetic (AFM) phase transition at T N = 5.7 K of EuTiO3 is rapidly suppressed with Sr doping in Eu x Sr1?x TiO3. Close to x = 0.25, T N = 0 K and AFM order vanishes. Above this critical concentration a finite transition temperature to an AFM phase is observed. The exchange couplings are derived as a function of x and the corresponding low temperature phase diagram is presented. 相似文献
20.
J. Todorović 《Solid State Communications》1977,21(9):919-921
A magnon soft mode in Mn2-xCrxSb in the vicinity of the Brillouin zone boundary in c1 direction, for the first order antiferro-ferrimagnetic phase transition, and the magnetization curve of the antiferromagnetic phase were measured. It was found that the soft mode energy squared is a linear function of temperature over a wide temperature range below and above the phase transition point. 相似文献