scholarly journals Dynamical mean-field study of the ferromagnetic transition temperature of a two-band model for colossal magnetoresistance materials

2006 ◽  
Vol 73 (18) ◽  
Author(s):  
F. Popescu ◽  
C. Şen ◽  
E. Dagotto
Keyword(s):  
Transition Temperature ◽  
Field Study ◽  
Colossal Magnetoresistance ◽  
Mean Field ◽  
Band Model ◽  
Ferromagnetic Transition ◽  
Two Band Model

Effects of clustering and dimensionality on the magnetic properties of diluted magnetic semiconductors

2003 ◽  
Vol 794 ◽  
Author(s):  
R. N. Bhatt ◽  
Malcolm. P. Kennett ◽  
Adel Kassaian
Keyword(s):  
Magnetic Properties ◽  
Transition Temperature ◽  
Diluted Magnetic Semiconductors ◽  
Magnetic Semiconductors ◽  
Mean Field ◽  
Impurity Band ◽  
Growth Conditions ◽  
Band Model ◽  
Ferromagnetic Transition ◽  
Diluted Magnetic

ABSTRACTThe magnetic properties of films of diluted magnetic semiconductors (DMS) such as (Ga,Mn)As, as well as bulk grown crystals of similar materials, have been found to be extremely sensitive to growth conditions, both in terms of the ferromagnetic transition temperature, and the details of their magnetization curves. We study an impurity band model for carriers in Mn-doped DMS applicable in the low carrier density regime, and discuss the effects of clustering on the magnetic properties of DMS, using both numerical mean field and Monte Carlo simulations. In addition, we study the effects of dimensionality on the transition temperature and other magnetic behaviour, and compare our results with experimental data.

scholarly journals Two Band Model for Diluted Magnetic Semiconductors: Study of the Ferromagnetic Transition Temperature

2011 ◽  
Vol 21 (2) ◽  
pp. 125
Author(s):  
Vu Kim Thai ◽  
Hoang Anh Tuan
Keyword(s):  
Transition Temperature ◽  
Diluted Magnetic Semiconductors ◽  
Magnetic Semiconductors ◽  
Magnetic Coupling ◽  
Coupling Constants ◽  
Band Model ◽  
Ferromagnetic Transition ◽  
Impurity Bands ◽  
Diluted Magnetic ◽  
Two Band Model

The ferromagnetic transition temperature (Tc) of a two band model for diluted magnetic semiconductors (DMS) is calculated by using the coherent potential approximation (CPA). It is shown that Tc is strongly parameter dependent on density of the carriers, magnetic coupling constants, and the hopping terms. The maximal Tc of the two band model is found when both impurity bands fully overlap and this value is approximately twice larger than the highest Tc obtained in the single band model.

Effect of Zn substitution on para- to ferromagnetic transition temperature in La0.67Ca0.33Mn1−xZnxO3 colossal magnetoresistance materials

2000 ◽  
Vol 87 (9) ◽  
pp. 5034-5036 ◽  
Author(s):  
V. P. S. Awana ◽  
E. Schmitt ◽  
E. Gmelin ◽  
Anurag Gupta ◽  
A. Sedky ◽  
...  
Keyword(s):  
Transition Temperature ◽  
Colossal Magnetoresistance ◽  
Ferromagnetic Transition ◽  
Zn Substitution

The nuclear relaxation rate for the itinerant-electron antiferromagnet

1982 ◽  
Vol 60 (5) ◽  
pp. 649-653 ◽  
Author(s):  
M. Crişan ◽  
Zs. Gulácsi
Keyword(s):  
Field Theory ◽  
Relaxation Rate ◽  
Mean Field Theory ◽  
Mean Field ◽  
Band Model ◽  
Itinerant Electron ◽  
Nuclear Relaxation ◽  
The Mean ◽  
Two Band Model ◽  
Good Agreement

The relaxation rate in the nuclear magnetic resonance of the itinerant-electron antiferromagnet was calculated as a function of temperature. A good agreement with the experimental results obtained on CrB2 has been observed. The two band model for the itinerant-electron antiferromagnet for T < TN (TN is the critical temperature) and the mean field theory for the critical region have been used to calculate [Formula: see text] as a function of temperature.

ISOTOPE EFFECTS OF Mn AND O IN COLOSSAL MAGNETORESISTIVE MANGANITES

2005 ◽  
Vol 19 (30) ◽  
pp. 4427-4436
Author(s):  
JE HUAN KOO ◽  
GUANGSUP CHO
Keyword(s):  
Transition Temperature ◽  
Curie Temperature ◽  
Colossal Magnetoresistance ◽  
Manganese Oxides ◽  
Isotope Effects ◽  
Kondo Lattice ◽  
Ferromagnetic Transition ◽  
Colossal Magnetoresistive ◽  
Kondo Lattice Model ◽  
Peierls Transition

We investigate theoretically manganese oxides where the colossal magnetoresistance (CMR) is observed. We obtain the Curie temperature Tc using a Kondo lattice model for paramagetic to ferromagnetic transition. We also acquire the charge-ordered transition temperature TCO applying spin-Peierls transition. We calculate the isotope exponents of Mn ion and O ion such as αc for Tc and αCO for TCO. Calculated αc of O ion is less than 0.9 and αCO is ~-(0.1~0.9).

scholarly journals Band Degeneracy and the Mott Transition: Dynamical Mean Field Study

1997 ◽  
Vol 11 (06) ◽  
pp. 729-751 ◽  
Author(s):  
Henrik Kajueter ◽  
Gabriel Kotliar
Keyword(s):  
Hubbard Model ◽  
Field Study ◽  
Mean Field ◽  
Mott Transition ◽  
Band Model ◽  
Infinite Dimensions ◽  
Orbital Degeneracy ◽  
Atomic Exchange ◽  
The One

We investigate the Mott transition in infinite dimensions in the orbitally degenerate Hubbard model. We find that the qualitative features of the Mott transition found in the one-band model are also present in the orbitally degenerate case. Surprisingly, the quantitative aspects of the density driven Mott transition around density one are not very sensitive to orbital degeneracy, justifying the quantitative success of the one-band model which was previously applied to orbitally degenerate systems. We contrast this with quantities that have a sizeable dependence on the orbital degeneracy and comment on the role of the intra-atomic exchange J.

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