6,226 research outputs found
Quantum Phase Transition from a Spin-liquid State to a Spin-glass State in the Quasi-1D Spin-1 System Sr1-xCaxNi2V2O8
We report a quantum phase transition from a spin-liquid state to a spin-glass
state in the quasi-one dimensional (1D) spin-1 system Sr1-xCaxNi2V2O8, induced
by a small amount of Ca-substitution at Sr site. The ground state of the parent
compound (x = 0) is found to be a spin-liquid type with a finite energy gap of
26.6 K between singlet ground state and triplet excited state. Both
dc-magnetization and ac-susceptibility studies on the highest Ca-substituted
compound (x = 0.05) indicate a spin-glass type magnetic ground state. With
increasing Ca-concentration, the spin-glass ordering temperature increases from
4.5 K (for the x = 0.015 compound) to 6.25 K (for the x = 0.05 compound). The
observed results are discussed in the light of the earlier experimental reports
and the theoretical predictions for a quasi-1D spin-1 system.Comment: 26 pages, 8 figures, 3 table
Magnetocaloric effect and critical behavior near the paramagnetic to ferrimagnetic phase transition temperature in TbCo2-xFex
Magnetocaloric effect (MCE) in TbCo2-xFex has been studied by dc
magnetization measurements.On substituting Fe in TbCo2, not only the magnetic
transition temperature is tuned to room temperature, but also the operating
temperature range for MCE is increased from 50 K for TbCo2 to 95 K for
TbCo1.9Fe0.1. The maximum magnetic entropy change (-{\Delta}SM) for
TbCo1.9Fe0.1 is found to be 3.7 J kg-1 K-1 for a 5 T field change, making it a
promising candidate for magnetic refrigeration near room temperature. The
temperature dependent neutron diffraction study shows a structural phase
transition (from cubic to rhombohedral phase with lowering of temperature)
which is associated with the magnetic phase transition and these transitions
broaden on Fe substitution. To investigate the nature of the paramagnetic to
ferrimagnetic phase transition, we performed a critical exponent study. From
the derived values of critical exponents, we conclude that TbCo2 belongs to the
3D Heisenberg class with short-range interaction, while on Fe substitution it
tends towards mean-field with long-range interaction. The derived values of
critical exponents represent the phenomenological universal curve for the field
dependence of {\Delta}SM, indicating that TbCo2 and TbCo1.9Fe0.1 belong to two
different universality classes.Comment: 12 figure
Magnetic studies of colossal magnetoresistance perovskites on macroscopic, mesoscopic and microscopic length scales
We have investigated magnetic correlations in various CMR manganites on macroscopic, mesoscopic and microscopic length scales by carrying out DC magnetization, neutron depolarization, and neutron diffraction measurements. We present here the effect of substituting Mn with Fe and La with Dy in the ferromagnetic La0.7−xCaxMnO3 (x ∼ 0.3–0.33) compounds. Neutron diffraction has been used in order to characterize the long-range magnetic order and its gradual suppression by the substitution. Neutron depolarization study has been carried out in order to bridge the gap in our understanding regarding the nature of magnetic correlation obtained from the macroscopic and microscopic measurements. In particular, our study on La0.67Ca0.33Mn0.9Fe0.1O3 has established the fact that a true double exchange mediated spin-glass is insulating. In another study of La-site ionic size effect and its disorder in (La1−xDyx)0.7Ca0.3MnO3, we have investigated the evolution of the length scale of magnetic ordering with a possible microscopic explanation and the results have been compared with that for the light rare earth substituted compounds
Assessment of Crop Farmers Indigenous Knowledge on the Use of Climate Change Adaptation Strategies in Lavun Local Government Area of Niger State, Nigeria
This study examined the crop farmers’ indigenous knowledge on the use of climate change adaptation strategies in Lavun Local Government Area of Niger State. A multi-stage random sampling technique was used to select 85 respondents. Data were collected using questionnaire and analyzed using descriptive and inferential statistics. The results reveal that majority (87.1%) were male with a mean age of 41years. Majority (69%) of the respondents were married and most (78%) had formal education and most (73%) of the them had no contact with extension agent with an average annual household income was ₦125,000. The result also depicts that most (91.8%) of the respondents were aware of climate change mostly on increase in temperature (85.9%), early/late cessation of rain and draught (64.7%). Among the indigenous knowledge used by the respondents as climate change adaptation strategies were changes in dates of planting (74.0%), mixed farming (55.0%) and diversification in crop production (49.0%). The result of the relationships between socio-economic characteristics and awareness to climate change indicates that; marital status, level of education and extension contact are significant respectively at p≤0.05 level of significance. The major constraints to the use of indigenous knowledge as climate change adaptation strategies were inadequate knowledge on how to cope (77.6%), poor response to adverse effect (61.2%), identified high cost of improved crop variety (57.6%) and low income level (48.2%). It was concluded that, respondents were able to develop indigenous adaptation strategies and marital status, level of education and extension contact were significantly related with climate change awareness. The study recommended that extension service should be increase for a successful adaptation programme, relevant information on climate change adaptation practices should reach the farmers through radio stations, news-papers, public lectures, seminars as well as other mass media means and provision of improved crop varieties at affordable price to the farmers
A secure data outsourcing scheme based on Asmuth – Bloom secret sharing
The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.Data outsourcing is an emerging paradigm for data management in which a database is provided as a service by third-party service providers. One of the major benefits of offering database as a service is to provide organisations, which are unable to purchase expensive hardware and software to host their databases, with efficient data storage accessible online at a cheap rate. Despite that, several issues of data confidentiality, integrity, availability and efficient indexing of users’ queries at the server side have to be addressed in the data outsourcing paradigm. Service providers have to guarantee that their clients’ data are secured against internal (insider) and external attacks. This paper briefly analyses the existing indexing schemes in data outsourcing and highlights their advantages and disadvantages. Then, this paper proposes a secure data outsourcing scheme based on Asmuth–Bloom secret sharing which tries to address the issues in data outsourcing such as data confidentiality, availability and order preservation for efficient indexing
Two-dimensional Induced Ferromagnetism
Magnetic properties of materials confined to nanometer length scales are
providing important information regarding low dimensional physics. Using
gadolinium based Langmuir-Blodgett films, we demonstrate that two-dimensional
ferromagnetic order can be induced by applying magnetic field along the
in-plane (perpendicular to growth) direction. Field dependent exchange coupling
is evident in the in-plane magnetization data that exhibit absence of
hysteresis loop and show reduction in field required to obtain saturation in
measured moment with decreasing temperature.Comment: 4 pages, 3 postscript figures, corrected paper forma
Implementasi Kebijakan Verifikasi Perizinan Usaha Guna Peningkatan Pendapatan Asli Daerah Kabupaten Gresik (Studi Pada Badan Penanaman Modal Dan Perizinan Kabupaten Gresik)
Abstrack : Licensing Verification Policy Implementation for Enhanced Local Revenue Gresik ((Study on Investment and Licensing Board Gresik). This study was done because the industry is an object of the original income receipts through business licensing charges. Less maximum legal compliance of regulations Gresik local government, it becomes a case for itself for local governments to increase regional income through licensing levy. Thus the Board of Investment and Licensing Licensing Verification establish programs to Increased Revenue Gresik regency with verification forms that are made directly to the company that stands approximately 5 years and also conducted assessments of business licensing documents. Licensing Verification aims to achieve an increase in revenue through a levy Regional Business Licensing Verification
Long-range and short-range magnetic correlations, and microscopic origin of net magnetization in the spin-1 trimer chain compound CaNi3P4O14
Spin-spin correlations and microscopic origin of net magnetization in the
spin-1 trimer chain compound CaNi3P4O14 have been investigated by powder
neutron diffraction. The present study reveals a 3D long-range magnetic
ordering below 16 K where the magnetic structure consists of ferromagnetic
trimers that are coupled ferromagnetically along the spin-chain. The moment
components along the a and c axes arrange antiferromagnetically. Our study
establishes that the uncompensated moment components along the b axis result in
a net magnetization per unit cell. The magnetic structure, determined in the
present study, is in agreement with the results of recent first principles
calculation; however, it is in contrast to a fascinating experimental
prediction of ferrimagnetic ordering based on the periodicity of the exchange
interactions in CaNi3P4O14. Our study also confirms the presence of broad
diffuse magnetic scattering, due to 1D short-range spin-spin correlations, over
a wide temperature range below ~50 K down to a temperature well below the Tc.
Total neutron scattering analysis by the RMC method reveals that the dominating
spin-spin correlation above Tc is ferromagnetic and along the b axis. The
nearest neighbour spin-spin correlations along the a and c axes are found to be
weakly antiferromagnetic. The nature of the trimer spin structure of the
short-range state is similar to that of the 3D long-range ordered state. The
present investigation of microscopic nature of the magnetic ground state also
explains the condition required for the 1/3 magnetization plateau to be
observed in the trimer spin-chains. In spite of the S=1 trimer chain system,
the present compound CaNi3P4O14 is found to be a good realization of 3D magnet
below the Tc=16 K with full ordered moment values of ~2 mu_B/Ni2+ (1.98 and
1.96 mu_B/Ni2+ for two Ni sites, respectively) at 1.5 K.Comment: 10 pages, 8 figure
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