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There have been constant efforts to find exotic quantum spin-liquid (QSL) materials. Some of the transition metal insulators dominated by the direction dependent anisotropic exchange interaction (Kitaev model for honeycomb network of magnetic ions) are considered to be promising cases for the same. In such Kitaev insulators, QSL is achieved from the zero-field antiferromagnetic state by the application of magnetic field, suppressing other exchange interactions responsible for magnetic order. Here, we show that the features attributable to long-range magnetic ordering of the intermetallic compound, Tb5Si3 (T_N= 69 K), containing honey-comb network of Tb ions, are completely suppressed by a critical applied field, H_cr, in heat-capacity and magnetization data, mimicking the behavior of Kitaev physics candidates. The neutron diffraction patterns as a function of H reveal that it is an incommensurate magnetic structure that gets suppressed, showing peaks arising from multiple wave vectors beyond Hcr. Increasing magnetic entropy as a function of H with a peak in the magnetically ordered state is in support of some kind of magnetic disorder in a narrow field range after H_cr. Such a high-field behavior for a metallic heavy rare-earth system to our knowledge has not been reported in the past and therefore is intriguing., Journal of Physics: Condensed Matter, in press

We have investigated magnetic, structural and dielectric properties of Bi

The present work reports magnetic, magnetoelastic and magnetoelectric (ME) response of scandium (Sc) doped barium hexaferrite, BaFe

We report the crystallographic properties of RE2NiGe3 (RE=La, Ce) synthesized by arc melting. Rietveld refinement on the powder neutron diffraction (ND) data suggest both compounds are isostructural and crystallize in the non-centrosymmetric Er2RhSi3 type structure having hexagonal space group P 6¯2c. In the crystal structure of RE2NiGe3, two dimensional arrangements of nickel and germanium atoms lead to the formation of hexagonal layers with rare earth atoms sandwiched between them. Magnetic susceptibility measurements performed in low fields exhibit antiferromagnetic ordering in cerium compound around (To=) 3.2 K. Neutron diffraction measurements at 2.8 K (i.e., at T

The neutron powder diffractometers and the polarized neutron spectrometer at the Dhruva reactor, Trombay have been used extensively for magnetic studies of several class of important materials, suc...

India accounts for about 40% of undernourished children in the world which contribute to high morbidity and mortality in the country. Recently reports on deaths due to malnutrition among Tribal communities of Thane district in the State of Maharashtra were widely published in the newspapers and also communicated via other media. A rapid survey was undertaken to investigate the extent of the problem in selected villages of Thane district where the malnutrition deaths were reported. Information was collected from a total of 118 households in 4 villages on nutritional status through clinical examination anthropometry dietary intake and general socio-economic status. The results revealed that majority of the population belonged to Scheduled tribe community (95.8%). Data on food and nutrient intake indicated that rice is consumed as the major dietary staple in the region followed by ragi (Eleusine coracana) wheat (Triticum aestivum) and bajra (Pennisetum typhoideum). The average calorie intake per Consumption Unit (CU) was observed to be 1857 kcal which was less than the RDA by 23% and protein 30% (42g) less than the RDA. The percent distribution of children from 0-6 years of age according to nutritional status indicated that the overall prevalence of underweight (less than Median-2SD) among 0-6 year old children was 68.7% while that of severe underweight (less than Median-3SD) was 28.6%. The overall prevalence of stunting (less than Median-2SD) in the children of the 0-6 year age group was 60.4% while that of severe stunting (less than Median-3SD) was 38.5%. The index of current nutritional status and measure of wasting as indicated by weight for height showed overall prevalence as 30.2% and severe wasting as 4.4%. The results of the rapid survey indicated that various factors including health status of mothers dietary and socio-economic factors have been contributory to the malnutrition of the children and that malnutrition alone may not be the direct cause of the deaths that are reported in the media. (authors)

We report the crystallographic properties of RE2NiGe3 (RE=La, Ce) synthesized by arc melting. Rietveld refinement on the powder neutron diffraction (ND) data suggest both compounds are isostructural and crystallize in the non-centrosymmetric Er2RhSi3 type structure having hexagonal space group P 6¯2c. In the crystal structure of RE2NiGe3, two dimensional arrangements of nickel and germanium atoms lead to the formation of hexagonal layers with rare earth atoms sandwiched between them. Magnetic susceptibility measurements performed in low fields exhibit antiferromagnetic ordering in cerium compound around (To=) 3.2 K. Neutron diffraction measurements at 2.8 K (i.e., at T

Double exchange (DE)-mediated ferromagnetism in manganites, in which the Zener pair (Mn3+/Mn4+) is a key factor, is marked by the coexistence of the magnetic transition and the metal-insulator transition, thus distinguishing itself from superexchange (SE)-mediated ferromagnetism. Through detailed magnetization, transport and XAS studies, it was proposed by some of us that a unique magnetic pair-making effect occurs in Ru-substituted La0.6Pb0.4Mn1−xRuxO3 by virtue of variable valency of Ru and Mn. Ru ion, exhibiting a variable valency of Ru4+ and Ru5+, governs the DE-mediated coupling by initiating a magnetic pair-making effect with Mn3+ and Mn4+ states. Neutron diffraction measurements carried out on these compounds in the temperature range 4.2–500 K reveal the microscopic nature of magnetic ordering. Data obtained, in conjunction with data from other experimental techniques above, show that (i) Ru participates in the DE interaction with Mn for x⩽0.4, (ii) there is a weakening of DE due to depletion of Ru5+ for x>0.4, and (iii) SE ferromagnetic interactions are favored for x>0.4.

A dilute concentration of single phase Cobalt substituted Bismuth ferrite, BiFe1−XCoXO3; (x=0, 0.02) is prepared by sol-gel auto combustion method. Room temperature neutron diffraction patterns show no change in the crystal and magnetic structure upon cobalt doping. The calculation of magnetic moments shows 3.848 μB for Fe+ and 2.85 μB for Co3+. The cobalt is found to be in intermediate spin state.

Magnetic structure evolution of multiferroic hexagonal $YMn_{1-x}Fe_{x}O_{3}$ (${x} = 0, 0.05,$ and $0.1$) has been studied by carrying out detailed temperature-dependent neutron diffraction at zero- and 5T-fields. Thermodynamic data confirm antiferromagnetic ordering at $T_{N}$ in all the compositions. Our sub-$T_{N}$ neutron diffraction results assign the magnetic structure of pure $YMnO_3$ to $\Gamma_{1}$ irreducible representation. Over the perturbative-doping range, the magnetic configuration changes via $\Gamma_{1}+\Gamma_{2}$ for $YMn_{0.95}Fe_{0.05}O_{3}$ on to $\Gamma_{2}$ for $YMn_{0.9}Fe_{0.1}O_{3}$, as the maiden compositional analogue of spin-reorientation; its occurrence in temperature-domain already reported for several manganites. Moreover, while the large thermal isostructural changes observed above ${T}_{N}$ are subdued in the ordered state, small alterations by the applied 5T-field are relatively uniform across, confirming strong magneto-elastic nature of the system. Decrease of the ordered magnetic moment ($\mu_{ord}$) and planar magnetic frustration noted with Fe-doping is enhanced by the applied field, apparently through canting., Comment: 19 pages, 1 table, 9 figures, 32 (numbered) references (groups)

The compound FeMnO3 crystallizing in the mineral bixbyite structure has been prepared by mechanochemical synthesis achieved by high energy ball milling of starting compounds. The structure and magnetism have been studied using powder neutron diffraction and magnetization measurements. Magnetization measurements exhibits ferrimagnetism at 300 K and antiferromagnetic (TN) ordering around 36 K. Magnetic structure has been determined from the Rietveld analysis of the neutron diffraction pattern recorded at 300 K. Fe and Mn occupy both 8b and 24d sites in 1:1 ratio. Interaction between Fe and Mn atoms is antiferromagnetic. The ferrimagnetism arises due to anti-parallel alignment of unequal moments on 8b and 24d sites.

V79 Chinese hamster cells were constructed for stable expression of human cytochrome P450 3A4 with and without coexpression of human NADPH-cytochrome P450 oxidoreductase. Expression of the cDNAs was shown by Northern and Western analyses. Activity was tested by 6 beta-hydroxylation of testosterone for cytochrome P450 3A4 and by cytochrome c reduction for NADPH-cytochrome P450 reductase. Five V79 cell lines were obtained expressing cytochrome P450 3A4, human NADPH-cytochrome P450 oxidoreductase, and both. Cytochrome P450 3A4 activity depended highly on cytochrome P450 reductase activity, with lowest activity when only the parental Chinese hamster cytochrome P450 reductase was present, 5- and 10-fold higher when coexpressed with the human NADPH-cytochrome P450 reductase. Correspondingly, cytotoxic and genotoxic potency of aflatoxin B1 was increased by orders of magnitudes when human cytochrome P450 3A4 was coexpressed with the human NADPH-cytochrome P450 reductase. The effect of NADPH-cytochrome P450 reductase coexpression on cytochrome P450 3A4 activity was also tested by nifedipine oxidation and midazolam hydroxylation. Nifedipine oxidation was increased about 10-fold, 1-hydroxylation of midazolam and 4-hydroxylation of midazolam were increased 15-fold.

Results of exhaustive ferromagnetic resonance (FMR) measurements performed on amorphous (a-) alloys at temperatures ranging from 10 to 500 K are presented and discussed in the light of existing theoretical models. The peak-to peak FMR linewidth consists of two contributions: one originating from two-magnon and multiple-magnon scattering processes and the other arising from the Laundau - Lifshitz - Gilbert damping mechanism. for the alloys with , as in other re-entrant (RE) systems, increases exponentially as the temperature is lowered through the RE transition temperature . The Lande splitting factor is independent of both temperature and Co concentration, whereas the Gilbert damping parameter is temperature-independent but decreases with increasing x. For all the alloys in question, thermal demagnetization is mainly due to spin-wave (SW) excitations and the SW stiffness coefficient D renormalizes with temperature in accordance with the predictions of the itinerant-electron model. SW modes in the alloys with soften at and D possesses a reduced but finite value in the RE state. Competing interactions present in the parent alloy a- confine the direct exchange interactions (DEIs) to the nearest neighbours only and partial replacement of Fe with Co progressively tilts the balance in favour of ferromagnetic interactions between Fe spins with the result that DEIs now involve next-nearest neighbours too and the divergence in at low temperatures is completely suppressed for x > 4.

The magnetic structure of the quasi‐1D compound Ca3CoMnO6 (CCMO) has been determined by carrying out Rietveld analysis of low temperature neutron diffraction (ND) patterns. The magnetic measurements on CCMO have established that the compound exhibits a long range antiferromagnetic ordering (TN) around 15 K, and interesting magnetic properties below TN. In order to understand the correlation of the magnetic behavior with the magnetic structure, we have recorded ND patterns at temperatures across TN, from 2 K to 30 K and have also studied the influence of externally applied magnetic field on the magnetic ordering in CCMO. The magnetic field induces drastic changes in the pristine magnetic structure at temperatures below 15 K. We discuss here the parameters associated with magnetic structure of CCMO at low temperatures and the influence of external field on them.

Room temperature Neutron diffraction study of CoxZn1−xFe2O4 ferrite system for x = 0.3 and 0.5 synthesized using hydrothermal techniques is reported here. The results show that the system x = 0.3 exhibits magnetic moment 1.1 Bohr magneton while x = 05 sample exhibits 1.9 Bohr magneton at room temperature. These values agree well with magnetization measurements.

We have studied the effect of Dy doping on the crystal structure and magnetic properties in hexagonal YMnO3. Dy was substituted at Y site up to x = 0.20. Polycrystalline Y1−xDyxMnO3 (x = 0, 0.02, 0.05, 0.10, 0.15, and 0.20) were synthesized by solid state reaction method. Room temperature neutron diffraction (ND) provides evidence for no change in crystal structure but lattice parameters gets modify with respect to doping, low temperature magnetization measurements shows modification in Curie‐Weiss temperature and Neel temperature. These results are understood in terms of variation in frustration parameter due to Dy induced strain in Y plane of hexagonal YMnO3.

We have investigated the effects of substituting Dy with Y on the magneto‐elastic coupling in YMnO3 using neutron diffraction (ND), dielectric, and specific heat measurements. Polycrystalline Y1−xDyxMnO3 (x = 0, 0.05) was synthesized by solid state reaction method. Extensive ND measurements provide evidence for change in the lattice parameters, and ordered magnetic moment as a function of temperature. Dielectric results show that due to Dy doping, inverse S‐shape anomaly shifts to the lower temperature side which is also indicated by specific heat measurements. These results are understood in terms of modification in magnetoelastic coupling triggered by Dy induced strain in Y plane of YMnO3.We have investigated the effects of substituting Dy with Y on the magneto‐elastic coupling in YMnO3 using neutron diffraction (ND), dielectric, and specific heat measurements. Polycrystalline Y1−xDyxMnO3 (x = 0, 0.05) was synthesized by solid state reaction method. Extensive ND measurements provide evidence for change in the lattice parameters, and ordered magnetic moment as a function of temperature. Dielectric results show that due to Dy doping, inverse S‐shape anomaly shifts to the lower temperature side which is also indicated by specific heat measurements. These results are understood in terms of modification in magnetoelastic coupling triggered by Dy induced strain in Y plane of YMnO3.

A detailed analysis of the magnetization and ``zero-field'' M\"ossbauer data taken on the amorphous ${\mathrm{Fe}}_{90}$${\mathrm{Zr}}_{10}$ alloy in the temperature range 4.2--300 K reveals the following: (i) Spin-wave (SW) excitations at low temperatures, single-particle (SP) excitations and local-spin-density (LSD) fluctuations over a wide range of intermediate temperatures, and enhanced fluctuations in the local magnetization for temperatures close to the Curie temperature, ${\mathit{T}}_{\mathit{C}}$, contribute dominantly to the thermal demagnetization of spontaneous magnetization; (ii) SW modes soften at temperatures below the freezing temperature ${\mathit{T}}_{\mathit{f}}$, where long-range ferromagnetic order coexists with the cluster spin-glass order; (iii) the LSD fluctuations are completely suppressed when magnetic fields (H) higher than 5 kOe are applied and M(H,T) for Hg5 kOe is solely governed by the SW and SP excitations for temperatures up to 0.95${\mathit{T}}_{\mathit{C}}$; (iv) contrary to some earlier claims, the spin-wave stiffness coefficient does not depend on H in the field range 5 kOe\ensuremath{\le}H\ensuremath{\le}15 kOe; (v) the magnetic hyperfine-field distribution, P(${\mathit{H}}_{\mathrm{hf}}$), is bimodal and comprises two Gaussian distributions; (vi) the low-field spin fraction [ratio of the area under the low-field Gaussian curve to that under the P(${\mathit{H}}_{\mathrm{hf}}$)-vs-${\mathit{H}}_{\mathrm{hf}}$ curve] grows at the expense of the high-field spin fraction as the temperature is raised above T\ensuremath{\simeq}150 K and amounts to about 90% of the total Fe spins for T\ensuremath{\simeq}${\mathit{T}}_{\mathit{C}}$; and (vii) the spin-freezing process does not start abruptly at ${\mathit{T}}_{\mathit{f}}$ but proceeds gradually over a wide temperature range extending from 130 K (\ensuremath{\approxeq}3${\mathit{T}}_{\mathit{f}}$) down to 4.2 K. While the transverse spin freezing and the finite spin clusters (composed of antiferromagnetic Fe spins) plus ferromagnetic (FM) matrix models fail to explain some of our findings, the finite-FM-clusters--FM-matrix picture provides a satisfactory explanation for all the diverse aspects of the present results.

The interplay between ferromagnetism and charge-ordering in a manganite system, achieved by means of Ru substitution at Mn-site in a charge-ordered Bi0.4Ca0.6MnO3 system, has been investigated by using magnetization and neutron diffraction (ND) studies. ND experiments were carried out on polycrystalline samples of Bi0.4Ca0.6Mn1 − xRu x O3 (x = 0.1 and 0.2) as a function of temperature and also in presence of a magnetic field. The magnetic structure determined from the Rietveld refinement of ND data has been compared and discussed with the magnetization measurements. The magnetic properties observed from the ND measurements agree well with the magnetization measurements, giving more insight into the magnetism of these compounds.

Binary intermetallic compound Nd7Rh3, crystallizes in a Th7Fe3 type hexagonal structure in space group P63mc and has been reported to show two antiferromagnetic (AFM) phase transitions at 32 K and 10 K from magnetic susceptibility, and a field induced first-order magnetic transition at a field strength of 1 Tesla at 2 K from magnetization measurements. These magnetic properties are different from the isostructural counterparts like Tb7Rh3, Ho7Rh3, and Nd7Ni3. In order to understand the differences in the magnetic behaviour between Nd7Rh3 and other isostructural compounds, we have carried out neutron diffraction (ND) studies on polycrystalline Nd7Rh3, at various temperatures between 2 and 45 K. ND patterns were also recorded at T = 2K in the presence of applied magnetic fields from 0 to 1.5 Tesla. ND spectra on Nd7Ni3 and Ho7Rh3, for example, at 2 K in zero magnetic field exhibit a strong AFM peak at a Q ( = 4?Sin?/?) value of 0.32 and 0.38 ??1, respectively. However, ND spectra on Nd7Rh3, carried out at Focusing Crystal Diffractometer (FCD-Dhruva-Mumbai), diffractometers E6 and E9 (HZB-Berlin) using wavelengths ? = 1.48?, 2.45? and 2.8? respectively, at T = 2K in zero field do not exhibit any AFM peaks in the entire Q-range studied. Instead, long-range ferromagnetic order is established as evidenced by the intensity enhancement of the nuclear Bragg peaks. The lack of extra peaks in the ND patterns would imply that the magnetic order seen in magnetization could be of a k = 0 type which changes from one type to another on the application of magnetic field. The results of nuclear and magnetic structure refinement are discussed to explain the magnetic behaviour of Nd7Rh3, at low temperatures.

Contrary to earlier reports, a detailed ferromagnetic resonance (FMR) study in the critical region of Fe90−xCoxZr10 alloys with 0≤x≤10 shows that the critical exponents β and γ for spontaneous magnetization and initial susceptibility, respectively, which characterize the ferromagnetic (FM)‐paramagnetic (PM) phase transition at the Curie temperature, TC, possess values which are close to the three‐dimensional Heisenberg values and are independent of composition. The fraction of spins that participates in the FM‐PM phase transition possesses a value of 11% for the alloy with x=0 and increases with Co concentration x. The peak‐to‐peak FMR linewidth is governed by the Landau‐Lifshitz‐Gilbert relaxation mechanism in the critical region and the Lande splitting factor g and the Gilbert damping parameter λ are independent of temperature. While λ decreases with x, g has a constant value of 2.07±0.02.

Angular dependence of ferromagnetic resonance fields in amorphous Fe90−xCoxZr10 alloys with 0≤x≤10 has been measured for both in‐plane and out‐of‐plane sample geometries. This angular variation has been fitted to theoretical resonance expressions which take into account the uniaxial anisotropy. The uniaxial anisotropy field, Hk=2Ku/Ms, increases with Co concentration and scales with saturation magnetization, Ms.

A detailed ‘‘zero‐field’’ Mossbauer and ferromagnetic resonance (FMR) study of a‐Fe90−xCoxZr10 alloys with 0≤x≤10 reveals that (i) alloys with x≤2 exhibit at low temperatures properties that are reminiscent of reentrant spin glass behavior (ii) for such alloys, the hyperfine field distribution P(H) is bimodal and comprises two Gaussian distributions and the peak‐to‐peak FMR linewidth, ΔHpp, diverges exponentially for T

The IX Workshop on “Neutrons as Probes of Condensed Matter–Structures of Crystalline Materials” was jointly organized by Bhabha Atomic Research Centre (BARC) and Inter University Consortium for DAE Facilities (IUC-DAEF), India, from November 17-December 3, 1999. Mumbai Centre of IUC–DAEF held the meeting to prepare and enable researchers from universities and other national laboratories to use neutron beam facilities at the IOOMW Dhruva research reactor at BARC.

Ferromagnetic resonance (FMR) measurements have been performed on amorphous Ni81.6B18.4 alloy, using the parallel geometry, at a fixed microwave frequency of approximately 9.3 GHz in the temperature range 100