共查询到20条相似文献,搜索用时 46 毫秒
1.
Vibhav Pandey Vivek Verma R.P. Aloysius G.L. Bhalla R.K. Kotnala 《Solid State Communications》2009,149(21-22):869-873
The variation in structural, magnetic and magneto-transport properties of the double perovskite system (Ba0.8Sr0.2)2?xNdxFeMoO6 {0.0<X<0.5} induced by Nd3+ doping (electron doping) has been studied and compared. The samples were prepared by standard solid state reaction method in a reducing atmosphere. The parent compound showed a saturation magnetic moment value of 3.75 μB/f.u. at an applied field of 0.5 T and a change in magnetoresistance value up to 26% (77 K, 0.8 T). The Rietveld refinement of the X-ray diffraction data showed a continuous decrease in lattice parameters and Fe–Mo ordering with increasing Nd3+ doping. The Curie temperature was found to increase with Nd3+ doping (3 K per % of Nd) while the saturation magnetic moment values and magnetoresistance values were found to decrease. The observed variations in magnetic and magneto-transport properties of the system are explained on the basis of increasing antisite disorder defects and band filling effects induced by electron doping. We have observed the dominant role of band filling in determining the low field magnetoresistance of these systems. 相似文献
2.
《Journal of magnetism and magnetic materials》1987,69(3):285-298
Magnetostriction measurements, between ≈ 5 and 300 K, of powder aligned samples of the uniaxial compounds RECo5 (RE = Pr, Ho, Dy and Y) for strong applied magnetic fields up to 15 T are reported. The strains have been measured, parallel, perpendicular and at 45° form the c-axis, with the field applied also along these directions. These sets of measurements allow us to determine the six irreducible magnetoelastic coupling constants: λα11, λα21, related to the strain dependence of isotrop ic exchange, and λα12, λα22, λγ and λϵ, describing the strain dependence of the magnetocrystalline anisotropy ene rgy. Anomalies on the strains, associated with the spin reorientation (SR) regime are observed. The thermal variation of the strains is well explained by the standard magnetostriction model, including as ingredients exchange striction and the single-ion anisotropic one, as well as a dependence on the angle of reorientation under field. The point charge model of the crystalline magnetoelastic field is far from agreement with the present results. 相似文献
3.
JianHua Du HangDong Wang Qin Chen QianHui Mao Rajwali Khan BinJie Xu YuXing Zhou YanNan Zhang JinHu Yang Bin Chen ChunMu Feng MingHu Fang 《中国科学:物理学 力学 天文学(英文版)》2016,59(5):26-31
After successfully growing single-crystal Ta P, we measured its longitudinal resistivity(ρxx) and Hall resistivity(ρyx) at magnetic fields up to 9 T in the temperature range of 2-300 K. At 8 T, the magnetoresistance(MR) reached 3.28 × 105% at 2 K, 176%at 300 K. Neither value appeared saturated. We confirmed that Ta P is a hole-electron compensated semimetal with a low carrier concentration and high hole mobility of μh=3.71 × 10~5cm~2/V s, and found that a magnetic-field-induced metal-insulator transition occurs at room temperature. Remarkably, because a magnetic field(H) was applied in parallel to the electric field(E), a negative MR due to a chiral anomaly was observed and reached-3000% at 9 T without any sign of saturation, either, which is in contrast to other Weyl semimetals(WSMs). The analysis of the Shubnikov-de Haas(Sd H) oscillations superimposed on the MR revealed that a nontrivial Berry's phase with a strong offset of 0.3958, which is the characteristic feature of charge carriers enclosing a Weyl node. These results indicate that Ta P is a promising candidate not only for revealing fundamental physics of the WSM state but also for some novel applications. 相似文献
4.
E.R. Seidel F.J. Litterst W. Gierisch G.M. Kalvius 《Journal of magnetism and magnetic materials》1975,1(1):19-22
The magnetic behaviour of very dilute 57Fe(≈20 ppm) impurities in paramagnetic NixRh1?x (x = 0.42 and x = 0.55) alloys has been studied by Moessbauer spectroscopy in the temperature range between 11 and 0.05 K and in external fields up to 5.6 T. The magnetic moment associated with the Fe-impurity is determined via the dependence of the hyperfine magnetic field on applied magnetic field and temperature. Below 4.2 K deviations from a free spin behaviour are found. The saturation hyperfine field becomes dependent on the applied field, a behaviour which is typical for impurity spin compensation. This compensation decreases with Ni concentration. 相似文献
5.
L. Motevalizadeh N. Tajabor D. Sanavi Khoshnoud D. Fruchart F. Pourarian 《Journal of magnetism and magnetic materials》2012
The thermal expansion and magnetostriction of HoFe11−xCoxTi (x=0, 0.3, 0.7 and 1) intermetallic compounds were measured, using the strain gauge method in the temperature range 77–590 K under applied magnetic fields up to 1.5 T. Results show that for samples with x=0 and 0.3, both linear thermal expansion and linear thermal expansion coefficient exhibit anomalies below the Curie temperature. Below room temperature, the spontaneous volume magnetostriction decreases with Co content. For all compounds studied, the anisotropic magnetostriction shows similar behaviour in the measured temperature range. The magnetostriction compensation occurs above room temperature in all samples. The volume magnetostriction shows a linear dependence on the applied field and by approaching the Curie temperature this trend changes to parastrictive behaviour. The results of the spontaneous magnetostriction are discussed based on the local magnetic moment model. The contribution of magnetostriction attributed to the magnetic sublattices R and T (Fe or Co) is discussed. 相似文献
6.
G. M. Kalvius K. Nishiyama K. Nagamine T. Yamazaki J. Chappert O. Hartmann E. Karlsson R. Wäppling A. Yaouanc L. Asch 《Hyperfine Interactions》1984,18(1-4):497-502
Transverse field measurements on the rare-earths intermetallics REAl2 in their paramagnetic regime have previously been carried out [1]. To aid discrimination between inhomogeneous line broadening and RE fluctuations which both contribute to the damping of the transverseSR pattern, we have carried out zero field measurements on three selected compounds (PrAl2, GdAl2, DyAl2) between 300 and 25 K. A small longitudinal decoupling field (6 mT) was applied in some cases. The present data corroborate the findings of the transverse field study: The polarization rate increases rapidly when approaching magnetic order. The high temperature limit of the spin fluctuation rate is markedly different in the three compounds. The
+ diffuses rapidly in all REAl2 compounds. 相似文献
7.
D. Sanavi Khoshnoud F. Pourarian 《Journal of magnetism and magnetic materials》2009,321(23):3847-3853
The magnetostriction of the off-stoichiometric R2Fe17-type intermetallic compounds based on R2Fe14−xCoxSi2 (R=Y, Er, Tm and x=0, 4) was measured, using the strain gauge method in the temperature range 77-460 K under applied magnetic fields up to 1.5 T. All compounds show sign change and reduction in magnetostriction values compared to the R2Fe17 compounds by Si substitution. For Y2Fe14Si2 and Er2Fe14Si2, saturation behaviour is observed near magnetic ordering temperature (TC), whereas for Tm2Fe14Si2, saturation starts from T>143 K. Also, Co substitution has different effects on the magnetostriction of R2Fe14Si2 compounds. In Er2Fe10Co4Si2 and Tm2Fe10Co4Si2, saturation occurs below the spin reorientation temperature (TSR). In addition, in Er2Fe14Si2, a sign change occurs in the anisotropic magnetostriction (Δλ) as well as the volume magnetostriction (ΔV/V) at their TSR values. The volume magnetostrictions of the Tm-containing compounds show an anomaly around their TSR. In R2Fe14Si2 compounds, parastrictive behaviour is also observed in ΔV/V near their TC values. In addition, the magnetostriction of the sublattices is investigated. Results show that in R2Fe14Si2 compounds, the rare-earth sublattice contribution to magnetostriction is negative and comparable to the iron sublattice, whereas, in R2Fe10Co4Si2 compounds, the rare-earth sublattice contribution is positive and larger than Fe sublattice. These results are discussed based on the effect of Si and Co substitutions on the anisotropy field of these compounds. Influence of the spin reorientation transition on the magnetostriction of these compounds is discussed in terms of the anisotropic sublattice interactions. 相似文献
8.
《Journal of magnetism and magnetic materials》1987,68(2):177-189
Magnetostriction measurements, between ≈5 and 300 K, of powder magnetically aligned samples of the hexagonal compound NdCo5, in strong pulsed magnetic fields up to 15 T are reported. The measurement have been performed parallel, perpendicular and at 45° to the alignment c-axis, for the field also applied in those directions. This set of measurements allows us to determine the six irreducible magnetoelastic modes: λα11, λα21, related to the strain dependence of the isotropic exchange, and λα12, λα22, λγ, λϵ, related to the strain dependence of the crystalline field anisotropy energy. Anomalies on the strains, associated with the spin reorientation (SR) regime are observed, in particular at the temperatures of beginning, TSR1, and end, TSR2, of the SR. The thermal variation of the strains is explained by the standard magnetostriction model, including an ingredients: exchange striction (varying as m2Nd), single-ion anisotropy (varying as m3Nd), (where mNd is the reduc ed Nd sublattice magnetization), as well as an angular dependence of the form {sin2θ(H, T)−sin2θ(0, T)}, where θ(H, T) and θ(0, T), respectively, are the SR angles under field and spontaneous. The irreducible magnetoelastic coupling constants at 0 K have been estimated, although the point charge model is far from agreement with those results. 相似文献
9.
《Solid State Communications》1987,64(7):1057-1060
The magnetic ordering of the Gd sublattice in superconducting GdBa2Cu3O7-δ is studied by Mössbauer spectroscopy using the 86.5-keV gamma resonance of 155Gd. Below the Néel temperature of TN ≌ 2.4 K, the magnetic hyperfine field at the Gd nucleus reflects the increasing local sublattice magnetization extrapolating to a saturation value of Beff(T=0 K) ≌ 31.5 T. The effective magnetic hyperfine field is found to be parallel to the main axis of the electric-field-gradient tensor, which is characterized by an asymmetry parameter of n = 0.40 ± 0.05. The observed isomer shift and the value of Beff are typical for trivalent Gd compounds with negligible conduction-electron contributions. 相似文献
10.
The La1.32Sr1.68Mn2O7 layered manganite system has been studied by the low temperature electrical resistance and magnetoresistance under hydrostatic pressure up to 25 kbar. We have observe both, a Curie temperature (TC) and a metal-insulator transition (TMI) at 118 K in the ambient pressure. The applied pressure shifts the TMI to higher temperature values and induces a second metal-insulator transition (T2MI) at 90 K, in the temperature dependence of resistivity measurements. Also, the pressure suppresses the peak resistance abruptly at TC. When an external field of 5 T is applied, we have observed a large negative magnetoresistance of 300% at the transition temperature and a 128% at 4.5 K. However, the increased pressure decreases the magnetoresistance ratio gradually. When the pressure reaches its maximum available value of 25 kbar, the magnetoresistance ratio decreases at a rate of 1.3%/kbar. From our experimental results, the decrease of magnetoresistance ratio with pressure is explained by the pressure induced canted spin state which is not favor for the spin polarized intergrain tunneling in layered manganites. 相似文献
11.
《Journal of magnetism and magnetic materials》1993,118(3):L285-L289
Magnetic measurements were performed on the (GdxY1−x)Co2B2 compounds, in the temperature range 2–800 K and fields up to 70 kOe. YCo2B2 is a paramagnet. The (GdxY1−x)Co2B2 compounds with x≥0.2 shows a ferromagnetic type ordering. The saturation magnetization at 2 K coincides only with the contribution of gadolinium. The Curie temperatures are nearly linearly dependent on the composition. Above the Curie points, the thermal variations of the magnetic susceptibility can be described as a superposition of a temperature independent term ϰ0 on a Curie-Weiss behavior. The Curie constants are determined by the contribution of Gd3+ ions only. The ϰ0 values increase when the gadolinium content is greater. The observed properties are discussed in the wider framework of the magnetic behavior of cobalt in GdCoxBy compounds. 相似文献
12.
M. ErdemÖ. Özturk E. YucelS.P. Altintas A. VarilciC. Terzio?lu I. Belenli 《Physica B: Condensed Matter》2011,406(3):705-709
We have investigated the effect of addition of Gd in Bi1.8Pb0.35Sr1.9Ca2.1Cu3GdxOy superconductor with x=0, 0.1, 0.2, 0.3, 0.4 and 0.5. The samples were prepared using the standard solid-state reaction method. The activation energies, irreversibility fields (Hirr), upper critical fields (Hc2) and coherence lengths at 0 K (ξ(0)) were calculated from the resistivity versus temperature (R-T) curves under DC magnetic fields up to 7 T. The superconducting transition temperature, Tc, and activation energy, U0, were found to decrease with increase in Gd concentration and with increase in applied magnetic field. The offset transition temperature of the pure (Gd00) sample without applied magnetic field is 108 K, whereas for Gd05 sample, the offset transition temperature drops to 5 K with 7 T applied magnetic field. The activation energy of the Gd00 sample without applied magnetic field is 34,980 K, and for Gd05 sample with 7 T applied field it is 98 K. Hirr and Hc2 values also decrease with increase in Gd addition. The possible reasons for the observed degradation in microstructural and superconducting properties due to Gd addition were discussed. 相似文献
13.
R. Nirmala A.V. Morozkin A.K. Nigam 《Journal of magnetism and magnetic materials》2009,321(3):188-191
Magnetization and neutron diffraction studies have been performed on Ce4Sb3 compound (cubic Th3P4-type, space group I4¯3d, no. 220). Magnetization of Ce4Sb3 reveals a ferromagnetic transition at ∼5 K, the temperature below which the zero-field-cooled and field-cooled magnetization bifurcate in low applied fields. However, a saturation magnetization (MS) value of only ∼0.93μB/Ce3+ is observed at 1.8 K, suggesting possible presence of crystal field effects and a paramagnetic/antiferromagnetic Ce3+ moment. Magnetocaloric effect in this compound has been computed using the magnetization vs. field data obtained in the vicinity of the magnetic transition, and a maximum magnetic entropy change, −ΔSM, of ∼8.9 J/kg/K is obtained at 5 K for a field change of 5 T. Inverse magnetocaloric effect occurs at ∼2 K in 5 T indicating the presence of antiferromagnetic component. This has been further confirmed by the neutron diffraction study that evidences commensurate antiferromagnetic ordering at 2 K in zero magnetic field. A magnetic moment of ∼1.24μB/Ce3+ is obtained at 2 K and the magnetic moments are directed along Z-axis. 相似文献
14.
The zero-field 153Eu NMR in EuSe has been observed as a function of the pressure up to 14 kbar in the temperature range between 1.7 and 4.2 K. A sequent magnetic phase transition of NSNS-NNS-NNSS-NNN occurs with pressure at 1.7 K. In the NNSS state (2.0 ? P ? 4.8 kbar) the NMR frequency v is insensitive to the pressure. In the ferromagnetic state (P ? 4.8 kbar) v depends remarkably on the pressure, and the exchange interaction between the nearest Eu neighbours J1 is shown to increase rapidly with decreasing the Eu-Eu distance. The pressure dependences of the Eu hyperfine field suggest that the magnetic moment of a Eu2+ ion in the ferromagnetic state under pressure is smaller than the ideal saturation value at 0 K. 相似文献
15.
N. V. Volkov I. A. Gudim E. V. Eremin A. I. Begunov A. A. Demidov K. N. Boldyrev 《JETP Letters》2014,99(2):67-75
A comprehensive experimental and theoretical study of magnetic, magnetoelectric, thermal, and spectroscopic characteristics of HoGa3(BO3)4 gallium borate single crystals has been performed. A large magnetoelectric effect exceeding its values found in all iron and aluminum borates except HoAl3(BO3)4 has been observed. The magnetoelectric polarization of HoGa3(BO3)4 equals ΔP ba (B a ) ≈ ?1020 μC/m2 at T = 5 K in a magnetic field of 9 T. The theoretical treatment based on the crystal field model for rare-earth ions provides a unified approach for the consistent interpretation of all measured characteristics. The crystal-field parameters are determined. The temperature (in the 3–300 K range) and magnetic field (up to 9 T) dependences of the magnetization, the Schottky anomaly in the temperature dependence of the specific heat, and its shift in the field B ‖ c are described. To compare the thermal properties of HoGa3(BO3)4 with those of HoAl3(BO3)4 exhibiting record values of the polarization, the specific heat of HoAl3(BO3)4 at various B values and the temperature dependence of the polarization ΔP b (T) in the applied magnetic field of 9 T have been measured. 相似文献
16.
P. IranmaneshN. Tajabor M. Rezaee Roknabadi D. FruchartF. Pourarian 《Physica B: Condensed Matter》2011,406(18):3359-3362
Magnetoelastic properties of Nd6Fe13Cu intermetallic compound are reported. To study the magnetoelastic behaviour of this compound, the thermal expansion as well as the longitudinal (λl) and transverse (λt) magnetostriction were measured by using the strain gauge method in the selected temperature range of 80-500 K under applied magnetic fields up to 1.5 T. An anomaly and invar-type effects are observed in the linear thermal expansion and α(T) curves at the Néel temperature. The linear spontaneous magnetostriction decreases sharply by approaching the Néel temperature and also shows the short-range magnetic ordering effects when antiferromagnetic-paramagnetic transition occurs. In the low field region, the absolute values of the anisotropic magnetostriction are small and then start to increase with applied magnetic field. Each isofield curve of the anisotropic magnetostriction passes through a minimum and then approaches to zero with increasing temperature. This magnetostriction compensation arises from the difference in the magnetoelastic coupling constants of the sublattices in this compound. 相似文献
17.
《Journal of magnetism and magnetic materials》1987,66(3):379-384
The 57Fe Mössbauer spectra are recorded in Nd2(Fe1-xCox)14B at x = 0.25 in the temperature range 100 to 780 K. Tc the Curie temperature, B̄hf, the magnetic hyperfine field average over various Fe nuclei of the unit cell and its temperature coefficient α(B̄hf) in the vicinity of 300 K are found to be 760(5) K, 34.0(3) T and -0.08(1)% K-1, respectively. The magnetic moment at Fe atoms is estimated to increase up to 12% as a result of the partial substitution by Co atoms. The dependence of the fields upon temperature is observed to be least at the j2 and k2 sites as compared to the other sites of Fe. The results for the variation of Bhf at all of the six sites of Fe with respect to temperature are given. A site preference of Fe atoms for the j2 sites is observed. 相似文献
18.
B. SamantarayS.K. Srivastava S. Ravi 《Journal of magnetism and magnetic materials》2011,323(21):2622-2626
The magnetic dynamics of charge ordered Nd0.8Na0.2MnO3 compound was studied by measuring the temperature variation of magnetization for different magnetic fields up to 7 T and, the field variation of magnetization at different temperatures down to 5 K. This sample exhibits a charge-ordering transition at 180 K, followed by a weak ferromagnetic (FM) transition at around 100 K and a spin glass like transition below 40 K. Suppression of charge-ordering and spin glass like transition and increase in FM TC were observed with an increase in magnetic field. A reversible metamagnetic transition above a threshold field (Hf) of 4.5 T was observed at 130 K, followed by a saturation magnetization of 3.2 μB/f.u. However at 5 K, an irreversible field induced first order phase transition from charge ordered state to FM state was observed at Hf=5 T. For comparison, the temperature and field variations of magnetization were studied on a FM compound from the same series with the composition Nd0.90Na0.10MnO3. A clear FM transition with a TC of 113 K and a saturation magnetization of 4.3 μB/f.u was observed. 相似文献
19.
Mechanical and magnetic properties of the ZnO/Fe2O3 ceramic varistors have been examined by using mechanical analyzer, digital microhardness tester and vibrating sample magnetometer. The initial stress–strain behavior is found to be linear (elastic) then becomes nonlinear (plastic deformation) without reaching the failure limit up to the maximum available stress (0.07 MPa). The compressive elastic modulus varies between 0.2 and 0.8 MPa with Fe addition up to 0.50. Furthermore, an approximately monotonically linear decrease in VHN with increasing Fe content up to 50% has been observed for all applied loads, which closely resembles the behavior of the true hardness and the surface energy. The magnetic measurements revealed an antiferromagnetic to paramagnetic to transition for all Fe doped samples. The Fe free sample showed paramagnetic behavior down to 2 K. The Neel temperature moderately increased from 18 K at 0.05% Fe to 25 K at 0.5% Fe. The magnetization (M) versus applied magnetic field (H) did not reach saturation for all samples up to 9 Tesla. The saturated magnetization (per Fe contents) is low and found to decreases linearly at a rate of (−35 emu/g-Fe) in a clear manifestation of the strengthening of the antiferromagnetic exchange interaction with increasing Fe contents. 相似文献
20.
The lattice parameters of the compounds CeAl3, LaAl3, PrAl3, and GdAl3 have been measured with x-rays in the range . In spite of their similarity, a significant difference between CeAl3 and the other compounds is found in the relative volume change . This is attributed to an increasing admixture of Ce4+ with decreasing temperature. Furthermore, cristalline-field effects are observed in the case of PrAl3. 相似文献