scholarly journals Effects of antiferro-ferromagnetic phase coexistence and spin fluctuations on the magnetic and related properties of NdCuSi

APL Materials ◽  
2015 ◽  
Vol 3 (6) ◽  
pp. 066102 ◽  
Author(s):  
Sachin Gupta ◽  
K. G. Suresh ◽  
A. Das ◽  
A. K. Nigam ◽  
A. Hoser
Keyword(s):  
Phase Coexistence ◽  
Spin Fluctuations ◽  
Ferromagnetic Phase

POLARON AND SPIN-POLARON EFFECTS IN THE COLOSSAL MAGNETORESISTANCE

1999 ◽  
Vol 13 (29n31) ◽  
pp. 3808-3814 ◽  
Author(s):  
Y. M. MALOZOVSKY ◽  
J. D. FAN
Keyword(s):  
Phase Transition ◽  
Colossal Magnetoresistance ◽  
Manganese Oxides ◽  
Spin Diffusion ◽  
Magnetic Moments ◽  
Spin Fluctuations ◽  
Ferromagnetic Phase ◽  
Spin Polaron ◽  
Ferromagnetic Phase Transition ◽  
Polaron Formation

The polaron formation due to the strong interaction of electrons with the optical phonons in a layered manganese oxides is considered. The diffusion of nearly localized polarons in the presence of the spin-dependent and multiple scattering on the randomly oriented and/or distributed magnetic moments of atoms is considered. The spin diffusion coefficient in the case of the exchange interaction between the diffusive but nearly localized polarons is evaluated. It is shown that the polaron localization leads to the vanishing of the spin diffusion and hence the ferromagnetic phase transition. The spin-polaron effect caused by the interaction of polarons with the spin fluctuations further significantly reduces conductivity near the temperature of the ferromagnetic phase transition as shown.

scholarly journals Magnetic hardening and antiferromagnetic/ferromagnetic phase coexistence inMn1−xFexRu2SnHeusler solid solutions

2016 ◽  
Vol 94 (9) ◽  
Author(s):  
Jason E. Douglas ◽  
Emily E. Levin ◽  
Tresa M. Pollock ◽  
Juan C. Castillo ◽  
Peter Adler ◽  
...  
Keyword(s):  
Solid Solutions ◽  
Phase Coexistence ◽  
Ferromagnetic Phase ◽  
Magnetic Hardening

Study of antiferro – ferromagnetic phase coexistence in Ta doped HfFe2

2014 ◽  
Vol 448 ◽  
pp. 50-52 ◽  
Author(s):  
Pallab Bag ◽  
Sanjay Singh ◽  
P.D. Babu ◽  
Vasudeva Siruguri ◽  
Rajeev Rawat
Keyword(s):  
Phase Coexistence ◽  
Ferromagnetic Phase

SUPERCONDUCTIVITY IN THE HUBBARD MODEL WITH STRONG COULOMB REPULSION

1992 ◽  
Vol 06 (03n04) ◽  
pp. 321-357 ◽  
Author(s):  
YU. A. IZYUMOV ◽  
B. M. LETFULOV
Keyword(s):  
Magnetic Susceptibility ◽  
Hubbard Model ◽  
Order Parameter ◽  
Magnetic Moments ◽  
Effective Interaction ◽  
Coulomb Repulsion ◽  
Spin Fluctuations ◽  
Ferromagnetic Phase ◽  
Pair Breaking ◽  
Strong Coulomb

Within the Hubbard model with strong Coulomb interaction U ≫ t (the t-J model), the possibility is studied for the superconducting state to exist due to charge and spin fluctuations in a system. Within the generalized random phase approximation (GRPA) used earlier by the authors for the calculation of magnetic susceptibility, the effective interaction between electrons in the Cooper channel was calculated. The calculations were performed by the diagram technique for the Hubbard operators. In GRPA, the effective interaction takes into account all diagram sequences with fermion loops and spin Green functions. The effective interaction is expressed via dynamical magnetic and dielectric susceptibilities; therefore it is considerably enhanced near the boundaries of the paramagnetic phase's instability towards the appearance of magnetic order, or of a state with charge density wave. Equations for the strong coupling in a superconductor are derived for the normal Z and anomalous φ parts of the electron Green function, linearized in the order parameter φ. The superconducting transition temperature T c is calculated with various sets of parameters in the (t/U, n) plane, n being the electron concentration. It is shown that in the itinerant magnetism regime (n < nc), where there is no localized magnetic moments in the system, spin fluctuations in the vicinity of antiferromagnetic phase transition lead to electron coupling with d-type symmetry, in analogy to the case of weak Coulomb repulsion. In the localized magnetic moment regime (n > nc), a quasistatistical term appears in the magnetic susceptibility. This terms leads to the pair-breaking mechanism, acting analogously to magnetic impurities. The dynamical part of the susceptibility may result in pairing interaction; however, high values of T c can hardly be expected in this case because of the pair-breaking interaction with localized magnetic moments. In the "Hubbard 1" approximation, the critical concentration nc for band with symmetric density of states equals 2/3. For n > 0.88, CDW instability appears in the system. Near its boundary, charge fluctuations may lead to coupling interaction with trivial symmetry of the order parameter. However, the critical line of the CDW instability lies within the region of ferromagnetic phase, and superconductivity becomes suppressed due to spin splitting of the electron spectrum.

scholarly journals SUPERCONDUCTIVITY AND QUANTUM PHASE TRANSITIONS IN WEAK ITINERANT FERROMAGNETS

2003 ◽  
Vol 17 (28) ◽  
pp. 5081-5091
Author(s):  
T. R. KIRKPATRICK ◽  
THOMAS VOJTA ◽  
D. BELITZ ◽  
R. NARAYANAN
Keyword(s):  
Quantum Phase Transitions ◽  
Tricritical Point ◽  
Spin Fluctuations ◽  
P Wave ◽  
Ferromagnetic Phase ◽  
Correlation Effects ◽  
First Order ◽  
Spin Triplet ◽  
First Order Transition ◽  
Itinerant Ferromagnets

It is argued that the phase transition in low Tc clean itinerant ferromagnets is generically of first order, due to correlation effects that lead to a nonanalytic term in the free energy. A tricritical point separates the line of first order transitions from Heisenberg critical behavior at higher temperatures. Sufficiently strong quenched disorder suppresses the first order transition via the appearance of a critical endpoint. A semi-quantitative discussion is given in terms of recent experiments on MnSi and UGe 2. It is then shown that the critical temperature for spin-triplet, p-wave superconductivity mediated by spin fluctuations is generically much higher in a Heisenberg ferromagnetic phase than in a paramagnetic one, due to the coupling of magnons to the longitudinal magnetic susceptibility. This qualitatively explains the phase diagram recently observed in UGe 2 and ZrZn 2.

Lorentz microscopy study of magnetic domain walls in Fe-Cr-Co alloys

1978 ◽  
Vol 36 (1) ◽  
pp. 462-463
Author(s):  
Yalcin Belli
Keyword(s):  
Domain Walls ◽  
Magnetic Domain ◽  
Microscopy Study ◽  
Ferromagnetic Phase ◽  
Stable Phase ◽  
Magnetic Domains ◽  
Lorentz Microscopy ◽  
Magnetic Hardening ◽  
Electron Microscopes ◽  
Co Alloys

Fe-Cr-Co alloys have great technological potential to replace Alnico alloys as hard magnets. The relationship between the microstructures and the magnetic properties has been recently established for some of these alloys. The magnetic hardening has been attributed to the decomposition of the high temperature stable phase (α) into an elongated Fe-rich ferromagnetic phase (α1) and a weakly magnetic or non-magnetic Cr-rich phase (α2). The relationships between magnetic domains and domain walls and these different phases are yet to be understood. The TEM has been used to ascertain the mechanism of magnetic hardening for the first time in these alloys. The present paper describes the magnetic domain structure and the magnetization reversal processes in some of these multiphase materials. Microstructures to change properties resulting from, (i) isothermal aging, (ii) thermomagnetic treatment (TMT) and (iii) TMT + stepaging have been chosen for this investigation. The Jem-7A and Philips EM-301 transmission electron microscopes operating at 100 kV have been used for the Lorentz microscopy study of the magnetic domains and their interactions with the finely dispersed precipitate phases.

KONDO EFFECT AND LOCALIZED SPIN FLUCTUATIONS IN THE Zn-TRANSITION METAL SYSTEM

1971 ◽  
Vol 32 (C1) ◽  
pp. C1-221-C1-223
Author(s):  
P. J. FORD ◽  
C. RIZZUTO ◽  
E. SALAMONI ◽  
P. ZANI
Keyword(s):  
Transition Metal ◽  
Kondo Effect ◽  
Spin Fluctuations ◽  
Metal System ◽  
Transition Metal System

TRANSVERSE SPIN FLUCTUATIONS IN γ - Mn (37 % Fe) ALLOY

1988 ◽  
Vol 49 (C8) ◽  
pp. C8-183-C8-184 ◽  
Author(s):  
J. J. Milczarek ◽  
K. Mikke ◽  
E. Jaworska
Keyword(s):  
Spin Fluctuations ◽  
Transverse Spin
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