1,761 research outputs found
Influence of chemical and magnetic interface properties of Co-Fe-B / MgO / Co-Fe-B tunnel junctions on the annealing temperature dependence of the magnetoresistance
The knowledge of chemical and magnetic conditions at the Co40Fe40B20 / MgO
interface is important to interpret the strong annealing temperature dependence
of tunnel magnetoresistance of Co-Fe-B / MgO / Co-Fe-B magnetic tunnel
junctions, which increases with annealing temperature from 20% after annealing
at 200C up to a maximum value of 112% after annealing at 350C. While the well
defined nearest neighbor ordering indicating crystallinity of the MgO barrier
does not change by the annealing, a small amount of interfacial Fe-O at the
lower Co-Fe-B / MgO interface is found in the as grown samples, which is
completely reduced after annealing at 275C. This is accompanied by a
simultaneous increase of the Fe magnetic moment and the tunnel
magnetoresistance. However, the TMR of the MgO based junctions increases
further for higher annealing temperature which can not be caused by Fe-O
reduction. The occurrence of an x-ray absorption near-edge structure above the
Fe and Co L-edges after annealing at 350C indicates the recrystallization of
the Co-Fe-B electrode. This is prerequisite for coherent tunneling and has been
suggested to be responsible for the further increase of the TMR above 275C.
Simultaneously, the B concentration in the Co-Fe-B decreases with increasing
annealing temperature, at least some of the B diffuses towards or into the MgO
barrier and forms a B2O3 oxide
Anomalous Spin Dynamics of Hubbard Model on Honeycomb Lattices
In this paper, the honeycomb Hubbard model in optical lattices is
investigated using O(3) non-linear sigma model. A possible quantum non-magnetic
insulator in a narrow parameter region is found near the metal-insulator
transition. We study the corresponding dynamics of magnetic properties, and
find that the narrow region could be widened by hole doping.Comment: 9 pages, 12 figure
A Review of Artificial Intelligence Based Research Results in Agriculture and Livestock Industry
In recent years, China's agricultural and animal husbandry industry has gradually developed
towards scale and intelligence, a process that cannot be achieved without the progress and
implementation of scientific research. This article takes the Grassland Animal Husbandry
Traceability Big Data Inner Mongolia Autonomous Region Engineering Laboratory of Inner
Mongolia University of Science and Technology as an example, and introduces four research
results related to agriculture and animal husbandry in this laboratory
Coexistence of Itinerant Electrons and Local Moments in Iron-Based Superconductors
In view of the recent experimental facts in the iron-pnictides, we make a
proposal that the itinerant electrons and local moments are simultaneously
present in such multiband materials. We study a minimal model composed of
coupled itinerant electrons and local moments to illustrate how a consistent
explanation of the experimental measurements can be obtained in the leading
order approximation. In this mean-field approach, the spin-density-wave (SDW)
order and superconducting pairing of the itinerant electrons are not directly
driven by the Fermi surface nesting, but are mainly induced by their coupling
to the local moments. The presence of the local moments as independent degrees
of freedom naturally provides strong pairing strength for superconductivity and
also explains the normal-state linear-temperature magnetic susceptibility above
the SDW transition temperature. We show that this simple model is supported by
various anomalous magnetic properties and isotope effect which are in
quantitative agreement with experiments.Comment: 7 pages, 4 figures; an expanded versio
States in Chiral SU(3) Quark Model
In this work, we study the masses of states with
J^{PC}=0^{++}, 1^{++}, 1^{+-} and 2^{++} in the chiral SU(3) quark model, where
Q is the heavy quark (c or b) and q (q') is the light quark (u, d or s).
According to our numerical results, it is improbable to make the interpretation
of and (n=u, d) states
as X(3872) and Y(3940), respectively. However, it is interesting to find the
tetraquarks in the system
Existence of positive solutions for singular higher-order fractional differential equations with infinite-point boundary conditions
In this paper, we consider a class of singular fractional differential equations with infinite-point boundary conditions. The fractional orders are involved in the nonlinearity of the boundary value problem, and the nonlinearity is allowed to be singular with respect to not only the time variable but also to the space variable. Firstly, we give Green’s function and establish its properties. Then, we utilize the sequential technique and regularization to investigate the existence of positive solutions. Finally, we give an example of application of our result
Quantum Non-Magnetic state near Metal-Insulator Transition - a Possible Candidate of Spin Liquid State
In this paper, based on the formulation of an O(3) non-linear sigma model, we
study the two-dimensional Pi-flux Hubbard model at half-filling. A quantum
non-magnetic insulator is explored near the metal-insulator transition that may
be a possible candidate of the spin liquid state. Such quantum non-magnetic
insulator on square lattice is not induced by frustrations. Instead, it
originates from quantum spin fluctuations with relatively small effective spin
moments. In the strong-coupling limit, our results of the spin velocity and
spin order parameter agree with results obtained from earlier calculations.Comment: 6 pages, 6 figures, Version of publication in EPL, removing the
contents of honeycomb lattice and adding some contents of square lattic
Properties of A Class of Topological Phase Transition
The properties of a class of topological quantum phase transition (TQPT) are
analyzed based on a model proposed by Haldane. We study the effect of finite
temperature on this phase transition. We have found that finite temperature
would drive this TQPT to be a crossover, while it is stable against the weak
short range interaction. When the interaction is strong enough, however, this
TQPT is unstable and other states would emerge. Then we investigate the effect
of the on-site energy in the original haldane model. The critical difference
between our TQPT and the topological phase transition in conventional quantum
Hall system is discussed. Finally, we discuss the potential application of our
analysis to a topological phase transition proposed in a realistic system.Comment: 7 pages, 7 figures. Accepted by Phys. Rev.
Electronic structure, magnetic and optical properties of intermetallic compounds R2Fe17 (R=Pr,Gd)
In this paper we report comprehensive experimental and theoretical
investigation of magnetic and electronic properties of the intermetallic
compounds Pr2Fe17 and Gd2Fe17. For the first time electronic structure of these
two systems was probed by optical measurements in the spectral range of 0.22-15
micrometers. On top of that charge carriers parameters (plasma frequency and
relaxation frequency) and optical conductivity s(w) were determined.
Self-consistent spin-resolved bandstructure calculations within the
conventional LSDA+U method were performed. Theoretical interpetation of the
experimental s(w) dispersions indicates transitions between 3d and 4p states of
Fe ions to be the biggest ones. Qualitatively the line shape of the theoretical
optical conductivity coincides well with our experimental data. Calculated by
LSDA+U method magnetic moments per formula unit are found to be in good
agreement with observed experimental values of saturation magnetization.Comment: 16 pages, 5 figures, 1 tabl
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