On the magnetic-field-induced changes in the parameters of phase transitions

2002 ◽  
Vol 28 (2) ◽  
pp. 116-118 ◽  
Author(s):  
M. N. Magomedov
Keyword(s):  
Magnetic Field ◽  
Phase Transitions ◽  
Induced Changes ◽  
The Magnetic Field

SPECTRAL PROPERTIES AND SYMMETRIES OF DOUBLE COVERINGS OF GRAPHS WITH APPLICATIONS TO SUPERCONDUCTIVITY

2005 ◽  
Vol 15 (02) ◽  
pp. 301-324
Author(s):  
JACOB RUBINSTEIN ◽  
MICHELLE SCHATZMAN
Keyword(s):  
Magnetic Field ◽  
Phase Transition ◽  
Phase Transitions ◽  
Ground State ◽  
Spectral Properties ◽  
Embedded Graph ◽  
Symmetry Constraints ◽  
The Laplace Operator ◽  
The Magnetic Field ◽  
Double Coverings

Let M be a planar embedded graph, and let [Formula: see text] be its double covering. We count the multiplicity of the ground states of the Laplace operator on [Formula: see text] under certain symmetry constraints. The examples of interest for us are ladder-like graphs made out of n, identical rectangles. We find that in the case of an odd n, the multiplicity of the ground state is 2, and if n, is even, the ground state is simple. This result gives an answer to a conjecture by Parks on the type of phase transitions that can occur in a superconducting ladder: Parks conjectured that in the case when the magnetic field is one half fluxoid per rectangle, the phase transition would be continuous in the case of a ladder made out of two rectangles. Our result indeed implies Parks conjecture and generalizes it to any even ladder. The mathematics of this paper is a mixture of topology, symmetry arguments and comparison theorem between the eigenvalues of Laplace operators on graphs with well chosen boundary conditions.

scholarly journals HALL EFFECT STUDIES OF THE SUPERCONDUCTING FERROMAGNET UCoGe

2017 ◽  
Vol 35 (2) ◽  
Author(s):  
Danica Krstovska ◽  
Eden Steven ◽  
Andhika Kiswandhi ◽  
James S. Brooks
Keyword(s):  
Magnetic Field ◽  
Hall Effect ◽  
Anomalous Hall Effect ◽  
Simple Relation ◽  
Hall Resistance ◽  
Unusual Behavior ◽  
Perpendicular Component ◽  
Induced Changes ◽  
The Magnetic Field ◽  
Characteristic Field

We find that the Hall effect in a single crystal of UCoGe varies as a function of the angle  between the applied magnetic field and the easy magnetic axis up to fields of 18 T at 0.2 K, i.e. in the region where both superconductivity and ferromagnetic order coexist. Instead of following the conventional cos dependence the two components that com-prise the total Hall resistance, the anomalous and ordinary Hall effect, exhibit quite an unusual behavior with the field direction. The anomalous Hall effect is found to be determined by the parallel component of the magnetization. We sug-gest that the field induced changes in magnetization due to the field rotation play an important role in the observed unu-sual behavior. The ordinary Hall effect cannot be described by the simple relation to the perpendicular component of the magnetic field implying that this component of the Hall effect may be also affected by the variations in magnetization at the characteristic field (kink field). A field induced moment polarization is also observed in Hall effect as in magnetore-sistance, which advances previous findings in UCoGe. The Hall effect slope reverses sign at the kink field indicative of small but possible Fermi surface reconstruction around this field. Our findings show that in UCoGe multiple mecha-nisms contribute to the observed field induced moment polarization at the kink field.

Influence of the magnetic field on phase transitions in PrAlO3

2010 ◽  
Vol 108 (11) ◽  
pp. 116102 ◽  
Author(s):  
C. Filipič ◽  
V. Bobnar ◽  
S. Turczynski ◽  
D. A. Pawlak ◽  
M. Wencka ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Phase Transitions ◽  
The Magnetic Field

Pulsed magnetic field-induced changes in the meso- and nanostructure of Co49Ni21Ga30 martensite

2017 ◽  
Vol 10 (04) ◽  
pp. 1750044 ◽  
Author(s):  
G. Gerstein ◽  
Victor L’vov ◽  
Yuriy Chumlyakov ◽  
T. Niendorf ◽  
P. Krooß ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Axial Stress ◽  
Pulsed Magnetic Field ◽  
Martensitic Structure ◽  
Magnetic Field Pulse ◽  
Field Pulse ◽  
Twin Boundaries ◽  
Martensitic State ◽  
Induced Changes ◽  
The Magnetic Field

A near single-variant martensitic state of Co[Formula: see text]Ni[Formula: see text]Ga[Formula: see text] alloy was induced by a static axial stress of 66[Formula: see text]MPa. Upon application of a magnetic field pulse, the single-variant state of stressed specimen was transformed into a hierarchic martensitic structure at micron, submicron and nanometer scales. The martensitic structures, which were induced during the magnetic field pulse, did not disappear after the field was switched off. This stability of the field-induced martensitic structure is attributed to the appearance of additional twinning systems with hardly mobile twin boundaries.

scholarly journals Аномалии магнитной восприимчивости при фазовых переходах второго рода вне точки Кюри

2018 ◽  
Vol 60 (9) ◽  
pp. 1669
Author(s):  
Г.К. Чепурных ◽  
В.А. Чёрная ◽  
О.Г. Медведовская
Keyword(s):  
Magnetic Field ◽  
Magnetic Susceptibility ◽  
Phase Transitions ◽  
Critical Field ◽  
Landau Theory ◽  
Experimental Investigations ◽  
Magnetic Field Direction ◽  
Similarity And Difference ◽  
The Magnetic Field ◽  
Cobalt Fluoride

AbstractTaking into account the inexhaustible interest in studying the peculiarities of physical properties in the neighborhood of phase transitions and the growth of experimental investigations of cobalt fluoride, we have studied the peculiarities of magnetic susceptibility in the vicinity of the critical field H _C at which cobalt fluoride performs the second-order phase transition from the antiferromagnetic phase to the angular phase. It is discovered that in the magnetic field H ‖ C _4, the magnetic susceptibility becomes infinite at H → H _C. It is shown that as the magnetic field direction deviates from the C _4 axis, the magnetic susceptibility in the critical field H _C proves to be finite. It is also shown that the change in the magnetic susceptibility with the change in the magnetic field considerably decreases at extremely insignificant deviations of the field H from the C _4 axis. Since the calculations are performed in terms of the Landau theory of phase transitions, we pay attention to the similarity and difference between the obtained results and those in the vicinity of the Curie point obtained by using the Landau theory of phase transitions.

scholarly journals Индуцированные магнитным полем спин-модуляционные переходы в эпитаксиальных плeнках BiFeO-=SUB=-3-=/SUB=- с ориентацией (001)

2019 ◽  
Vol 61 (2) ◽  
pp. 248
Author(s):  
Н.Е. Кулагин ◽  
А.Ф. Попков ◽  
С.В. Соловьёв ◽  
А.К. Звездин
Keyword(s):  
Magnetic Field ◽  
Strain Engineering ◽  
Homogeneous State ◽  
Induced Anisotropy ◽  
Practical Applications ◽  
Homogeneous Phase ◽  
Growing Domain ◽  
The Stability ◽  
Induced Changes ◽  
The Magnetic Field

AbstractAlterations in the ground state of thin (001) films of a BiFeO_3 (BFO)-type multiferroic in a magnetic field are studied theoretically, with changes in the energy of induced anisotropy taken into account. The anisotropy vs. field phase diagrams identifying the stability regions of homogeneous antiferromagnetic states and the regions of emergence of spatially modulated antiferromagnetic states are constructed for three mutually orthogonal orientations of applied magnetic field. We show that, as the magnetic field decreases, the transformation of a homogeneous phase into a spatially modulated state occurs at the instability point of the homogeneous state via gradual emergence of the conical phase that transforms into a planar cycloid with the decreasing magnetic field. A multiferroic film grown on a (001) substrate develops considerable anisotropy of the energy of spatially modulated state, depending on the modulation orientation. Meanwhile, cycloids with different orientations undergo the transitions from incommensurate phase into the homogeneous state differently: either the conical cycloid is formed followed by its collapse into the homogeneous state or an unlimitedly growing domain of the homogeneous phase is formed within the flat cycloid. Examples of field-induced changes in magnetization, with changes in spin states taken into account, are provided. These results are of value in practical applications of multiferroic strain engineering.

Magnetostriction near the magnetic-field-induced phase transitions of Cr2O3

Physica B+C ◽  
1977 ◽  
Vol 86-88 ◽  
pp. 1126-1127 ◽  
Author(s):  
R.D. Yacovitch ◽  
Y. Shapira
Keyword(s):  
Magnetic Field ◽  
Phase Transitions ◽  
The Magnetic Field

scholarly journals Скачкообразные процессы магнитного разупорядочения, стимулированные магнитным полем в системах со структурной неустойчивостью

2020 ◽  
Vol 62 (5) ◽  
pp. 710
Author(s):  
В.И. Вальков ◽  
А.В. Головчан ◽  
В.В. Коледов ◽  
Б.М. Тодрис ◽  
В.И. Митюк
Keyword(s):  
Magnetic Field ◽  
Phase Transitions ◽  
Static Magnetic Fields ◽  
First Order ◽  
Temperature Dependences ◽  
Second Order Transition ◽  
First Order Phase ◽  
Experimental Pressure ◽  
The Magnetic Field ◽  
Theoretical Results

A theoretical analysis of the features of structural and magnetostructural first-order phase transitions in magnetocaloric helimagnetic alloys of the Mn_{1-x}Cr_{x}NiGe system has been carried out. To describe the observed displacive structural transitions hex(P6_{3}/mmc)<->orth(P_{nma}), we used the local soft mode model in the approximation of a biased harmonic oscillator. In the absence of a magnetic field, the emergence of a helimagnetic order as a structurally induced second-order transition was described in the framework of the Heisenberg model, taking into account the dependence of the exchange integrals on the structural order parameters and elastic strains. In the presence of a magnetic field, it was found that the approximation of the characteristic temperatures for the helimagnetic HM(P_{nma}) and lability temperatures of the hexagonal paramagnetic PM(P6_{3}/mmc) states, due to the influence of the magnetic field, leads to the appearance of previously unexplored peripheral magnetostructural first-order phase transitions with insignificant magnetization jumps that increase with increasing magnetic induction.In this case, as the pressure increases to 4 kbar with constant induction of the magnetic field, the peripheral transitions transform into reversible first-order magnetostructural transitions, and at even higher pressures (10-14 kbar) into full-fledged first-order magnetostructural transitions with magnetization jumps comparable with maximum value of magnetization. Experimental pressure studies of the temperature dependences of magnetization in static magnetic fields with an induction of up to 1 T and a pressure of up to 14 kbar confirm the theoretical results.

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