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1.
We measured the magnetic susceptibility of KC24 from 4.2 to 300 K and found no anomalies near the phase transitions at 95 and 123 K as observed in the resistivity. We conclude that the transitions must be due to order- disorder transitions of the K atoms and not charge density wave formation. The susceptibility is anisotropic; at room temperature and . This anisotropy is not understood in terms of simple rigid band extensions of the band structure of graphite. 相似文献
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3.
C. Rincón M. Quintero Ch. Power J.A. Henao G.E. Delgado M. Morocoima 《Solid State Communications》2011,151(13):947-951
In an attempt to resolve the crystal structure and the corresponding space group of the magnetic semiconductor Cu2FeSnS4, samples of this compound were studied by X-ray diffraction, differential thermal analysis, Raman scattering and magnetic susceptibility. It was found that at room temperature this compound prepared by a careful crystal growth process, including annealing to equilibrium at a suitable temperature followed by slow cooling of the samples to 300 K, crystallizes in a tetragonal structure with space group . 相似文献
4.
Transport measurements were performed on FeCr2S4 parallelepipeds with {100} faces, cut from vapour grown crystals. This made possible the separation of the spontaneous effect from the field dependent effect. The anisotropy of the latter effect only depends on the direction of B relative to the crystallographic axes. The anisotropy of the magnetoresistance has been analysed in terms of spin disorder scattering. 相似文献
5.
The infrared and visible cooperative emissions of ytterbium ions are studied in Yb-doped NdVO4 single crystals. The absorption of optical phonons allows the emissions at room temperature when a Nd:YAG laser is used. Low temperature emissions are observed due to the Nd3+→Yb3+ energy transfer following an argon ion laser excitation of the Nd3+ ions. Analysis of the cooperative emission at low doping concentration (1%) indicates that it is generated by distant pair forming Yb3+ ions while at high doping concentration (≥ 5%) close ions magnetically coupled and superexchange mechanisms prevail in the emitting process. 相似文献
6.
We report a successful crystal growth of Ca2Y2Cu5O10 and anisotropic behavior of magnetic susceptibility associated with an antiferromagnetic phase transition. Single crystals were obtained by the floating-zone method using an infrared radiation furnace. Composition and structural characterization shows that the grown crystals are qualified for physical measurements. The magnetic susceptibility along each crystallographic axis shows a typical behavior of antiferromagnetic phase transition at TN=31 K, and the ordered magnetic moments are found to lie along the b-axis. 相似文献
7.
A.V. Bogach G.S. Burkhanov O.D. Chistyakov V.V. Glushkov S.V. Demishev N.A. Samarin Yu.B. Paderno N.Yu. Shitsevalova N.E. Sluchanko 《Journal of magnetism and magnetic materials》2006
A comprehensive and high-precision magnetoresistance (MR) Δρ/ρ(H,T) and magnetization M(H,T) measurements have been carried out for two well known and archetypal magnetic strongly correlated electron systems—CeAl2 and CeB6. It was shown that the main Brillouin-type component of MR in these magnetic heavy fermion compounds can be consistently interpreted in the frameworks of a simple relation between resistivity and magnetization—Δρ/ρ∼M2 obtained by Yosida [Phys. Rev. 107 (1957) 396]. A local magnetic susceptibility χloc(T,H)=(1/H*(d(Δρ/ρ)/dH))1/2 was deduced directly from this part of MR and compared in details with the data of bulk susceptibility χ(T,H) measurements. Two additional contributions to MR have been also deduced for CeAl2 ((i) linear (∼H) and (ii) nanoscale ferromagnetic components) and applied for a characterization of spin polarons in this magnetic material. The dependencies χloc(T,H) and χ(T,H) obtained in this study for CeB6 and CeAl2 allow us to analyze the H–T magnetic phase diagram in these magnetic heavy fermion compounds. 相似文献
8.
S. GeorgescuO. Toma A.M. VoiculescuC. Matei R. BirjegaL. Petrescu 《Physica B: Condensed Matter》2012,407(7):1124-1127
Bright green (at 525 and 550 nm) and red (at 660 nm) luminescence in Er:Yb:La3Ga5.5Ta0.5O14 (LGT) powder synthesized by solid state reaction was obtained by pumping at 936 nm. Yb3+-Er3+ energy transfer processes accounting for population of the 2H211/2, 4S3/2 and 4F9/2 Er3+ levels are discussed. The dependence of ratio between the intensities of the green and red luminescence on pump intensity is analyzed. The rather high quantum efficiency (58%) of the (4S3/2, 2H211/2) Er3+ emitting level recommends LGT doped with erbium and ytterbium for upconversion applications. 相似文献
9.
D. J. Flood 《Physics letters. A》1977,60(5):463-464
Magnetic susceptibility measurement in the range 1.4 to 4.2 K reveal a maximum in χ at 3.65 K, and two maxima in Δχ/ΔT, one at 3.32 K (assumed to be TN), and another at 1.8 K. High field magnetization measurements indicate a saturation moment of 7 μB. 相似文献
10.
The temperature dependence of the magnetic susceptibility, Knight shift and specific heat for the compound CrAl7 have been measured. These measurements point out that, at the temperature around TN ≈220 K the compound CrAl7 presents a second order phase transition from the electron itinerant antiferromagnetism state to the paramagnetic state. The NMR and magnetic susceptibility measurements are correlated and the results are discussed in terms of the electron itinerant antifer-romagnetism and rigid band models. For the temperature independent-term of the susceptibility all the contributions are given. 相似文献
11.
The unusual anisotropy of an activation energy for the conductivity of highly pure La2CuO4 is explained in terms of disk-like polarons with large in-plane radius and small interplane one. For such a polaron the anisotropy of the mobility mechanism appears in a wide range of T: the in-plane hops are thermoactivated, while the interplane ones are due to the quantum tunneling. The T-dependence of Hall effect and the possibilities for the microscopic structure of a polaron in La2CuO4 are briefly discussed. 相似文献
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S.H. Kim B.H. Oh J.H. Han Cheol Eui Lee J.Y. Choi K.D. Hahn C.Y. Jang B.H. Youn J. Kim 《Current Applied Physics》2009,9(6):1307-1309
KH2PO4 single crystals have been studied by employing complex impedance measurements in view of the domain freezing effect. As a result, distinct behaviors of the anisotropic domain-wall dynamics in the activation energy of domain freezing and the Vogel–Fulcher temperature before and after proton irradiation have been identified in the anisotropic crystal structure. 相似文献
13.
Kuldeep Chand Verma Virender Pratap SinghMast Ram Jyoti ShahR.K. Kotnala 《Journal of magnetism and magnetic materials》2011,323(24):3271-3275
The structural, microstructural and magnetic properties of nanoferrite NiFe2O4 (NF), CoFe2O4 (CF) and MnFe2O4 (MF) thin films have been studied. The coating solution of these ferrite films was prepared by a chemical synthesis route called sol-gel combined metallo-organic decomposition method. The solution was coated on Si substrate by spin coating and annealed at 700 °C for 3 h. X-ray diffraction pattern has been used to analyze the phase structure and lattice parameters. The scanning electron microscopy (SEM) and atomic force microscopy (AFM) have been used to show the nanostructural behavior of these ferrites. The values of average grain's size from SEM are 44, 60 and 74 nm, and from AFM are 46, 61 and 75 nm, respectively, measured for NF, CF and MF ferrites. At room temperature, the values of saturation magnetization, Ms∼50.60, 33.52 and 5.40 emu/cc, and remanent magnetization, Mr∼14.33, 15.50 and 1.10 emu/cc, respectively, are observed for NF, CF and MF. At low temperature measurements of 10 K, the anisotropy of ferromagnetism is observed in these ferrite films. The superparamagnetic/paramagnetic behavior is also confirmed by χ′(T) curves of AC susceptibility by applying DC magnetizing field of 3 Oe. The temperature dependent magnetization measurements show the magnetic phase transition temperature. 相似文献
14.
Setsuo Misawa 《Solid State Communications》1974,15(3):507-509
Anomalous magnetic behaviour observed in one of cerium intermetallic compound, CeSn3, is analysed in the spirit of the Fermi liquid model, by regarding even the 4f-electrons of cerium as itinerant. It is shown that the appearance of the broad peak of the susceptibility at about 150°K can be attributed to the T21nT dependence of the susceptibility on temperature. 相似文献
15.
Neutron diffraction experiments have been performed on single crystal samples of U3P4 and U3As4. The magnetic ordering is found to be a non-collinear three axial structure in which magnetic moments of U4+ ions are tilted from the [111] axis by an angle of about twenty degrees within (110) planes. 相似文献
16.
J.E. Greedan Carl W. Turner D.A. Goodings 《Journal of magnetism and magnetic materials》1984,42(3):255-262
Bulk magnetization measurements have been performed on single crystals of HoTiO3 and ErTiO3. The easy direction of magnetization is along the b-axis for HoTiO3 and along the c-axis for ErTiO3 with respect to the Pbnm chemical cell. These findings are in qualitative agreement with the results of two independent powder neutron diffraction studies. The saturation magnetic moments at 4.2 K along the easy axes are 7.3(2)μB per formula unit for HoTiO3 and 6.9(2)μB for ErTiO3. In addition, single crystal susceptibility data were analyzed using the theory of Boutron to yield values for the Heisenberg exchange coupling and the second-order crystal field terms B02 and B22. 相似文献
17.
Infrared reflection spectra for the extraordinary ray of zircon and spondumene have been obtained in the frequency range from 270 to 1500 cm?1 and from room temperature up to 1300°K. Using a combination of Kramers-Kronig analysis and a classical dispersion theory, the oscillator parameters of the A2u modes in zircon and Au modes in spodumene were determined. The temperature dependence of observed mode damping is analysed on the basis of quantum theoreticall results involving both cubic and quartic anharmonic contributions. The comparison of the present results with other data reported in previously studied silicate crystals, shows that the observed anharmonic behavior of internal and external modes is consistent with simple considerations based on the site vicinity of each ion. 相似文献
18.
The infrared (IR) and 57Fe-Mössbauer spectra of Fe3IIFe4III(AsO4)6 were recorded and analyzed on the basis of its structural characteristics. The IR spectrum presents a high complexity, showing an important number of bands and splittings, as a consequence of the presence of three structurally independent AsO43− groups. The analysis of the four quadrupole signals shown by the Mössbauer spectrum allowed to attain a detailed insight into the cation distribution over the available crystallographic sites. The alternating current susceptibility measurements indicate a paramagnetic to ferrimagnetic transition in the material at about 59 K. 相似文献
19.
The magnetic susceptibility of 2H-TaSe2 is temperature dependent and anisotropic. The susceptibility with H parallel to the c axis is approximately 2.5 times that perpendicular. The decrease in susceptibility below the charge density wave transition at 122 K is also anisotropic with [χ6(122 K) ? χ6(4.2 K]?[χ⊥(122 K) ? χ⊥(4.2 K)] ≈ 4. Consequently, this change cannot be simply interpreted as a change in the density of states at the Fermi level, unless very anisotropic electron g values are assumed. 相似文献
20.
John B. Gruber Raylon M. Yow Uygun V. Valiev Gary W. Burdick 《Journal of luminescence》2008,128(8):1271-1284
Detailed analyses of spectroscopic and temperature-dependent magnetic susceptibility data are reported for the crystal-field split energy levels of the 7FJ and 5D4 of Tb3+ in stoichiometric single crystals of ortho-aluminate TbAlO3. The spectroscopic data include absorption spectra obtained between 2940 and 480 nm from 8 to 300 K. High resolution fluorescence spectra are reported, representing transitions from 5D4 to 7F6,5,4, at a sample temperature of 85 K. Using crystal-field modeling techniques recently adapted for low symmetry systems, we have assigned all 58 experimental Stark levels within the 7FJ and 5D4 manifolds, with a fitting standard deviation of 4.5 cm−1 (3.8 cm−1 rms error). As a further test, the theoretical Stark levels and calculated wavefunctions were used to determine the temperature dependence of the magnetic susceptibility along the c-axis of the TbAlO3 crystal. Good agreement is obtained between the calculated susceptibility and temperature-dependent magnetic data reported earlier, including a prediction of a 0.2 cm−1 splitting of the ground-state quasi-doublet. The susceptibility calculation also confirms the predicted ordering of states within the 7F6 multiplet manifold. 相似文献