On the possibility of magnetic ordering (TC(N)) induced by a surface exchange interaction in an Ising nanoparticle with TC(N) > TC(B), where TC(B) is a transition temperature in the corresponding bulk system

2020 ◽  
Vol 530 ◽  
pp. 110588 ◽  
Author(s):  
T. Kaneyoshi
Keyword(s):  
Transition Temperature ◽  
Exchange Interaction ◽  
Magnetic Ordering ◽  
Surface Exchange ◽  
Bulk System

scholarly journals Фазовый переход в цилиндрических изинговых нанопроволоках и нанотрубках: приближение теории молекулярного поля

2019 ◽  
Vol 61 (4) ◽  
pp. 694
Author(s):  
В.А. Танрывердиев ◽  
В.С. Тагиев ◽  
М.Н. Абдуллаев ◽  
Г.Г. Керимова
Keyword(s):  
Field Theory ◽  
Phase Diagram ◽  
Transition Temperature ◽  
Exchange Interaction ◽  
Critical Behavior ◽  
Exchange Coupling ◽  
Molecular Field ◽  
Physical Parameters ◽  
Surface Exchange ◽  
The Core

AbstractWithin the approximation of the molecular field theory, the critical behavior of cylindrical Ising nanowires and nanotubes is studied. The model considered in this work consists of ferromagnetic spins S _c situated in the core of the system and ferromagnetic spins S _s situated on the surface wall; they are interconnected by the exchange coupling J _1. The transition temperature T _c for such systems has been calculated as a function of exchange interaction parameters. The influence of the surface exchange interaction and surface coupling on the magnetodynamic behavior of the system have been studied. Some characteristic properties obtained on the phase diagram are related to the ratio of characteristic physical parameters on the surface and core of the abovementioned nanostructures.

Magnetic Ordering of Perovskite-Like La-, Nd-, and Gd-Doped Bismuth Ferrite

MRS Advances ◽  
2019 ◽  
Vol 4 (36) ◽  
pp. 1989-1999 ◽  
Author(s):  
Valery Sobol ◽  
Barys Korzun ◽  
Olga Mazurenko ◽  
Temirkhan Bizhigitov ◽  
Sabit Tomaev
Keyword(s):  
Magnetic Field ◽  
Exchange Interaction ◽  
Bismuth Ferrite ◽  
Magnetic Ordering ◽  
Solid State Reaction Method ◽  
Nonlinear Dependence ◽  
X Ray Diffraction ◽  
Wide Range ◽  
Pure Grade ◽  
The Magnetic Field

ABSTRACTBismuth ferrite (BiFeO3) and La-, Nd- and Gd-substituted bismuth ferrite of the Bi1-xLaxFeO3, Bi1-xNdxFeO3, and Bi1-xGdxFeO3 types with the atomic part of the substitution element x equal up to 0.20 were synthesized by the solid-state reaction method using powders of oxides Bi2O3, Fe2O3, and La2O3, or Nd2O3, or Gd2O3 of pure grade quality and investigated using X-ray diffraction analysis. The magnetization was measured in the magnetic field up to 6.5⋅106 A/m at 5 and 300 K. It was found that the total substitution up to 0.20 atomic part of Bi by La, Nd, and Gd leads to the paramagnetic behavior of the doped bismuth ferrite at low temperatures in a wide range of magnetic field. Strong nonlinear dependence of magnetization on the magnetic field was detected and a ferromagnetic-like dependence of magnetization was observed for small magnetic fields. This can be explained by the exchange interaction between doping magnetic ions, as well as by the exchange interaction of these ions with ions of iron. The enhancement of magnetic properties with the increase of the content of the substitution is monotone and is more pronounced for the Bi1-xGdxFeO3 ceramics.

Negative magnetization, complex magnetic ordering and applications of Cr-doped Co2TiO4

2020 ◽  
Vol 22 (13) ◽  
pp. 7058-7064
Author(s):  
Q. S. Fu ◽  
X. H. Chen ◽  
C. Chakrabarti ◽  
C. L. Li ◽  
J. Zheng ◽  
...  
Keyword(s):  
Exchange Interaction ◽  
Magnetic Ordering ◽  
Negative Magnetization

Negative magnetization, exchange interaction and possible applications of Cr-doped Co2TiO4 ceramics have been investigated in detail.

Enhancement of superconducting transition temperature near surface of bulk system

2007 ◽  
Vol 460-462 ◽  
pp. 1381-1383 ◽  
Author(s):  
Hirono Kaneyasu ◽  
Yasumasa Hasegawa ◽  
Tetsu Nobukuni ◽  
Kenji Makoshi
Keyword(s):  
Transition Temperature ◽  
Superconducting Transition Temperature ◽  
Superconducting Transition ◽  
Near Surface ◽  
Bulk System

Alteration of the stacked 2π/3 magnetic structure in the triangular lattice anti-ferromagnet LiCrS2

2001 ◽  
Vol 79 (11-12) ◽  
pp. 1427-1432
Author(s):  
A Lafond ◽  
W Henggeler ◽  
H Mutka ◽  
B Ouladdiaf
Keyword(s):  
Transition Temperature ◽  
Critical Temperature ◽  
Solid State ◽  
Elastic Scattering ◽  
Temperature Dependence ◽  
Triangular Lattice ◽  
Magnetic Ordering ◽  
Magnetic Scattering ◽  
Powder Samples ◽  
Anisotropic Interactions

LiCrS2 has magnetic Cr ions with spin S = 3/2 on a triangular lattice. Other researchers (J. Solid State Chem. 3, 590, 1971) concluded that this compound has an anti-ferromagnetic order with a stacked 2π/3 structure below a transition temperature of the order of TN = 50 K. We have re-examined this system with neutron scattering methods on powder samples, paying attention to the temperature dependence of the magnetic scattering. The overall characteristics of the magnetic ordering are in agreement with the earlier study but we have observed significant modifications of the stacked 2π/3 structure well below the critical temperature. The main new features observed on cooling from T = 25 K down to T = 1.5 K are (i) the gradual decrease from 2.5 µB to 2.3 µB of the ordered moment attributed to the 2π/3 structure, (ii) the appearance of new correlations corresponding to a multiplication of the magnetic unit cell, and (iii) the growth of a diffuse elastic scattering component that can be ascribed to a frozen disorder. These observation are not explained in the framework of the standard theoretical treatments concerning the stacked triangular anti-ferromagnet with Heisenberg or slightly anisotropic interactions. PACS Nos.: 75.10Nr, 75.25+z, 75.40Gb

COEXISTENCE OF SUPERCONDUCTIVITY AND FERROMAGNETISM IN UGe2

2003 ◽  
Vol 17 (26) ◽  
pp. 1385-1389 ◽  
Author(s):  
JE HUAN KOO ◽  
GUANGSUP CHO
Keyword(s):  
Transition Temperature ◽  
Exchange Interaction ◽  
Coulomb Interaction ◽  
High Transition Temperature ◽  
Previous Model ◽  
Electron Interaction ◽  
Electron Pairs ◽  
High Transition

We investigate the coexistence of ferromagnetism and superconductivity in UGe 2 and Sr 2 RuO 4 in analogy with our previous model3 for high transition temperature superconductivity (HTSC). The Coulomb interaction for triplet electron pairs is reduced by a difference of the exchange interaction. If the electron–electron interaction Usf for UGe 2 and Usd for Sr 2 RuO 4 are larger than the reduced Coulomb interaction, superconductivity must happen. Under the same conditions, the coexistence of superconductivity and ferromagnetism is impossible in the case of our scheme, but changing phonons by pressures makes the coexistence possible for UGe 2.

scholarly journals PROBLEMS OF COEXISTENCE OF SUPERCONDUCTIVITY AND MAGNETIC ORDERING OF COPPER SUBLATTICES IN YBa2Cu3-XFeXO7-X CERAMICS

2020 ◽  
Vol 1 ◽  
pp. 57-62
Author(s):  
M Ruzieva ◽  
Q Bobomurodov ◽  
S Bobomurodov ◽  
R Shokirov
Keyword(s):  
Solid Solution ◽  
Mössbauer Spectroscopy ◽  
Transition Temperature ◽  
Oxygen Content ◽  
Superconducting State ◽  
Mossbauer Spectroscopy ◽  
Magnetic Ordering ◽  
Orthorhombic Lattice ◽  
Antiferromagnetic Ordering ◽  
Superconducting Ceramics

The article studies the problems of coexistence of superconductivity and magnetic ordering of copper sublattices in YBa2Cu3-xFexO7-x ceramics. It is known that in superconducting ceramics YBa2Cu3O7-z with orthorhombic lattice as the oxygen content decreases, the transition temperature in superconducting state Tc decreases, and at z>0.6 superconductivity disappears, the lattice becomes tetragonal and at the same time, antiferromagnetic ordering of sublattices Cu (2) appears. The substitution in ceramics of YBa2Cu3O7 part of copper atoms by iron atoms (i.e., the formation of a solid solution of YBa2Cu3-xFexO7+y) is accompanied by similar effects: as x increases, Tc decreases, at x>0.05 the orthorhombic lattice becomes tetragonal, at x>0.45 the superconductivity disappears. The most significant moment is the fact of coexistence in ceramics YBa2Cu3-xFexO7+y in the region of compositions 0.03 < x < 0.45 of superconductivity and magnetic ordering of iron atoms in copper nodes (the latter is established by Mossbauer spectroscopy on isotope 57Fe in a large number of works. However, it remains unclear whether the magnetic ordering of iron atoms in the YBa2Cu3-xFexO7+y lattice is related to the magnetic ordering of copper atoms

Structural and magnetic properties on F-doped LiVO2 with two-dimensional triangular lattice

2011 ◽  
Vol 1344 ◽  
Author(s):  
Yang Li ◽  
Xiaoxiang Li ◽  
Lihua Liu ◽  
Ning Chen ◽  
Jose García ◽  
...  
Keyword(s):  
Phase Transition ◽  
Transition Temperature ◽  
Thermal Hysteresis ◽  
Magnetic Ordering ◽  
Lattice Parameter ◽  
Two Dimensional ◽  
Scanning Calorimetry ◽  
Heat Measurement ◽  
Dsc Measurements ◽  
First Order Phase Transition

ABSTRACTThe layered oxide LiVO2 recently has received more attention due to its interesting structural and magnetic behaviors involving the two-dimensional magnetic frustration in these systems. We synthesized a series of F-doped LiVO2 samples, and reported the F-doping effect on the structure and transition temperature Tt. The samples LiVO2-xFx (x=0, 0.1, 0.2 and 0.3) were characterized by X-ray diffraction, scanning electron microscope (SEM), differential scanning calorimetry (DSC), magnetic susceptibility and specific heat measurement. The structural analysis shows that with increasing x, the ratio of lattice parameter c/a increasing, i.e. in the a-b plane the lattice is compressed while in the c-axis direction the lattice expands. The DSC measurements show that a first-order phase transition happens at around 500 K, and the thermal hysteresis around phase transition temperature Tt increases with increasing x. Substitution of O with F ions results in a change of two dimensional characteristics and the distortion of the VO6 block in structure, which significantly influence the magnetic ordering transition temperature Tt.

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