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31.
Sengupta K Alzamora M Fontes MB Sampathkumaran EV Ramos SM Hering EN Saitovitch EM Paulose PL Ranganathan R Doert T Jemetio JP 《J Phys Condens Matter》2012,24(9):096004
The influence of external pressure on the electrical transport and magnetic properties of EuCu(2)As(2), crystallizing in a ThCr(2)Si(2)-type structure, is reported. The system is known to be an antiferromagnet below T(N) ≈ 15 K in the absence of external magnetic fields. We find that there is a gradual reduction of T(N) with the application of a magnetic field with an extrapolated value of the critical field of around 18 kOe which can drive T(N) to zero. Electrical resistivity under pressure (<11 GPa) reveals that the magnetic ordering temperature is pushed up dramatically to higher temperatures which is quite interesting if compared with the behavior in isostructural FeAs-based systems containing Eu. Above 7 GPa, the pressure-induced state appears to be ferromagnetic. The results thus reveal interesting changes in the magnetic ordering behavior of this compound with increasing pressure and magnetic fields. 相似文献
32.
The magnetic behavior of binary compound CeIn(2) has been reported to be unusual in the sense that this compound appears to exhibit a first-order ferromagnetic transition at a rather high temperature of (T(C)=)22 K, which is not so common for Ce systems. In order to throw more light on the magnetic behavior of this compound, we have carried out detailed magnetization, and electrical resistivity studies as a function of temperature, magnetic field and external pressure, in addition to heat-capacity measurements. The plots of H/M versus M(2) at low fields are interestingly characterized by negative slopes, not only near T(C), but also at lower temperatures, a source of which could be attributed to magnetic-field-induced transitions at much lower temperatures. The sign of magnetoresistance tends to change from positive to negative with increasing temperature, as though there is a gradual change in the magnetic character. Finally, the magnetic ordering temperature increases with increasing pressure (until 20 kbar), as though this compound lies at the left-hand side of the peak in Doniach’s magnetic phase diagram. 相似文献
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34.
The magnetic behavior of a solid solution, Ca3 x Yx CO2 O6, based on the ‘exotic’ spin-chain compound, Ca3Co2O6, crystallizing in K4CdCl6-derived rhombohedral structure is investigated. Among the compositions investigated(x = 0.0, 0.3, 0.5, 0.75 and 1.0), single-phase formation persists up tox = 0.75, with the elongation of the c-axis. The present investigations reveal that the temperature at which the ‘so-called’
‘partially disordered antiferromagnetic structure’ sets in (which occurs at 24 K for the parent compound,x = 0.0) undergoes gradual reduction with the substitution of Y for Ca, attaining the value of about 2.2 K for the nominalx = 1.0. The trend observed in this characteristic temperature is opposite to that reported under external pressure, thereby
establishing that Y substitution exerts negative chemical pressure. Anomalous steps observed in the isothermal magnetization
at very low temperatures (around 2 K) forx = 0.0, which have been proposed to arise from ‘quantum tunneling effects’ are found to vanish by a small substitution (x = 0.3) of Y for Ca. Systematics in AC and DC magnetic susceptibility behavior with Y substitution for Ca have also been probed.
We believe that the present results involving the expansion of chain length without disrupting the magnetic chain may be useful
to the overall understanding of the novel magnetism of the parent compound. 相似文献
35.
We have grown single crystals of the psuedo-one-dimensional compound Sr3CuIrO6, a K4CdCl6-derived monoclinic structure with Cu-Ir chains along the [101] direction. We present the ac and dc magnetization behavior
of the single crystals in comparison with that of the polycrystalline form reported earlier. There is a distinct evidence
for at least two magnetic transitions, at 5 K (T
1) and 19 K (T
2), with different relative magnitudes in the single and polycrystals. The low temperature magnetic relaxation behavior of
both the forms is found to be widely different, exhibiting unexpected time dependence. 相似文献
36.
Sampathkumaran EV Sengupta K Rayaprol S Iyer KK Doert T Jemetio JP 《Physical review letters》2003,91(3):036603
We report an unusual temperature (T) dependent electrical resistivity (rho) behavior in a class of ternary intermetallic compounds of the type RCuAs2 (R=rare earths). For some rare earths (Sm, Gd, Tb, and Dy) with negligible 4f hybridization, there is a pronounced minimum in rho(T) far above respective Néel temperatures (T(N)). However, for the rare earths which are more prone to exhibit such a rho(T) minimum due to 4f-covalent mixing and the Kondo effect, this minimum is depressed. These findings, difficult to explain within the hitherto-known concepts, present an interesting scenario in magnetism. 相似文献
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38.
E. V. Sampathkumaran 《Hyperfine Interactions》1986,27(1-4):183-192
The current status of the phenomenon of intermediate valence in rare earth systems is surveyed. Particular attention is paid
to the merits and demerits of various experimental methods employed to obtain the value of the mean valence of the rare earth
ion, followed by the discussion on the cerium problem. 相似文献
39.
J. Deisenhofer H.-A. Krug von NiddaA. Loidl E.V. Sampathkumaran 《Solid State Communications》2003,125(6):327-331
We report electron-spin resonance (ESR) measurements in polycrystalline samples of (Gd1−xYx)2PdSi3. We observe the onset of a broadening of the linewidth and of a decrease of the resonance field at approximately twice the Néel temperature in the paramagnetic state. This characteristic temperature coincides with the electrical resistivity minimum. The high-temperature behavior of the linewidth is governed by a strong bottleneck effect. 相似文献
40.
E.V. Sampathkumaran Niharika Mohapatra Kartik K. Iyer C.D. Cao W. Löser G. Behr 《Journal of magnetism and magnetic materials》2008
Considering certain interesting features in the previously reported 166Er Mössbauer effect, and neutron diffraction data on the polycrystalline form of ErPd2Si2 crystallizing in the ThCr2Si2-type tetragonal structure, we have carried out magnetic measurements (1.8–300 K) on the single crystalline form of this compound. We observe significant anisotropy in the absolute values of magnetization (indicating that the easy axis is c-axis) as well as in features due to magnetic ordering in the plot of magnetic susceptibility χ versus temperature T at low temperatures. The χ(T) data reveal that there is a pseudo-low-dimensional magnetic order setting in at 4.8 K, with a three-dimensional antiferromagnetic order setting in at a lower temperature (3.8 K). A new finding in the χ(T) data is that, for H∥〈1 1 0〉 but not for H∥〈0 0 1〉, there is a broad shoulder in the range 8–20 K, indicative of the existence of magnetic correlations above 5 K as well, which could be related to the previously reported slow-relaxation-dominated Mössbauer spectra. Interestingly, the temperature coefficient of electrical resistivity is found to be isotropic; no feature due to magnetic ordering could be detected in the electrical resistivity data at low temperatures, which is attributed to magnetic Brillioun-zone boundary gap effects. The results reveal the complex nature of magnetism of this compound. 相似文献