Optical spectral weights and the ferromagnetic transition temperature of colossal-magnetoresistance manganites: Relevance of double exchange to real materials

2000 ◽  
Vol 61 (16) ◽  
pp. 10738-10749 ◽  
Author(s):  
A. Chattopadhyay ◽  
A. J. Millis ◽  
S. Das Sarma
Keyword(s):  
Transition Temperature ◽  
Colossal Magnetoresistance ◽  
Double Exchange ◽  
Ferromagnetic Transition

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

SPIN CORRELATIONS OF THE MAGNETORESISTIVE BILAYER MANGANITE La1.2Sr1.8Mn2O7

1999 ◽  
Vol 13 (29n31) ◽  
pp. 3820-3822
Author(s):  
S. Rosenkranz ◽  
R. Osborn ◽  
J. F. Mitchell ◽  
L. Vasiliu-Doloc ◽  
J. W. Lynn ◽  
...  
Keyword(s):  
Colossal Magnetoresistance ◽  
Double Exchange ◽  
Hole Mobility ◽  
Ferromagnetic Transition ◽  
Double Exchange Interaction ◽  
Metal Insulator ◽  
Spin Correlations ◽  
Paramagnetic Region ◽  
X Ray Scattering ◽  
Good Agreement

We review our recent neutron and X-ray scattering studies of the 40% hole doped bilayer manganite La 1.2 Sr 1.8 Mn 2 O 7, which exhibits colossal magnetoresistance above the ferromagnetic transition at T C~113 K. In the paramagnetic region, static diffuse scattering reveals the existence of correlated charges. However, the good agreement of the in-plane spin correlations with the conventional model for quasi two-dimensional XY magnets indicates that the metal-insulator transition is driven by the growth of magnetic correlations. Across the transition, the competition between antiferromagnetic superexchange and ferromagnetic double exchange, observed as canted correlations between spins in neighboring layers within each bilayer, is strongly reduced, indicating a direct link of the double exchange interaction to the hole mobility.

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).

High Pressure Measurements on TI2Mn2O7

1999 ◽  
Vol 602 ◽  
Author(s):  
M. Núñez-Regueiro ◽  
R. Senis ◽  
W. Cheikh-Rouhou ◽  
P. Strobel ◽  
P. Bordet ◽  
...  
Keyword(s):  
High Pressure ◽  
Transition Temperature ◽  
Pressure Dependence ◽  
Colossal Magnetoresistance ◽  
Structural Changes ◽  
Structural Parameters ◽  
Applied Pressure ◽  
Ferromagnetic Transition ◽  
Pressure Measurements ◽  
Electronic Band

AbstractTransport and structural properties of the colossal magnetoresistance pyrochlore TI2Mn2O7 are studied as a function of applied pressure up to ∼20GPa. This allows us to probe the effect of structural changes on the ferromagnetic transition and the transport properties. We observe a non-monotonous pressure dependence of the ferromagnetic transition temperature. We correlate this unusual variation with the structural parameters that, according to electronic band calculations, are key in controlling the properties of these materials.

Structure, Electrical and Magnetic Properties of Thin Films of La1−xMxMnO3 on Si

1999 ◽  
Vol 562 ◽  
Author(s):  
N. N. Mateeva ◽  
P. C. Hogan ◽  
K. H. Dahmen
Keyword(s):  
Thin Films ◽  
Magnetic Properties ◽  
Transition Temperature ◽  
Buffer Layers ◽  
Ferromagnetic Transition ◽  
Electrical And Magnetic Properties ◽  
Insulator Metal Transition ◽  
Composition Structure

ABSTRACTThin films of lanthanum manganates doped with Ca2+, Sr2+, Ba2+ and Pb2+ have been deposited on Si(100) substrate and their electrical and magnetic properties were discussed with respect to the composition, structure and nature of the dopant. Buffer layers of YSZ and La0.8Al0.2O3 were employed and their effect on the materials was studied. Interesting magnetotransport properties were found in some of the films, where there is a large difference between the insulator-metal transition temperature and a ferromagnetic transition temperature.

Decrease of Ferromagnetic Transition Temperature in Nonstoichiometric SrRu1−v O3 Perovskites

2002 ◽  
pp. 303-311
Author(s):  
B. Dabrowski ◽  
P. W. Klamut ◽  
O. Chmaissem ◽  
S. Kolesnik ◽  
M. Maxwell ◽  
...  
Keyword(s):  
Transition Temperature ◽  
Ferromagnetic Transition

Effect of Low Temperature Annealing on High Field Magnetoresistance and Hall effect in (Ga, Mn)As Dilute Magnetic Semiconductors

2004 ◽  
Vol 831 ◽  
Author(s):  
K. Ghosh ◽  
Mohammad Arif ◽  
T. Kehl ◽  
R. J. Patel ◽  
S. R. Mishra ◽  
...  
Keyword(s):  
Transition Temperature ◽  
Low Temperature ◽  
High Field ◽  
Magnetic Semiconductors ◽  
Magnetic Semiconductor ◽  
Dilute Magnetic Semiconductors ◽  
Epitaxial Thin Films ◽  
Ferromagnetic Transition ◽  
Optimal Temperature ◽  
Low Temperature Annealing

ABSTRACTIn this paper we report the effect of low temperature annealing on the high field magnetotransport properties of epitaxial thin films of (Ga, Mn)As Dilute Magnetic Semiconductor (DMS) with low concentration (1.5 %) of Mn doping, which results in a ferromagnetic insulator. Annealing at an optimal temperature enhances the conductivity, carrier concentration, and ferromagnetic transition temperature. The field dependence of magnetoresistance is different below and above the ferromagnetic transition temperature. An attempt is made to analyze the data using a theoretical model proposed by Kaminski and Das Sarma [1].

EFFECTS OF PHOTO-EXCITATION AND MAGNON SCATTERING ON FERROMAGNETIC TRANSITION TEMPERATURE OF THE DILUTED MAGNETIC SEMICONDUCTOR (Ga1 - x, Mnx)As

2011 ◽  
Vol 25 (04) ◽  
pp. 273-280 ◽  
Author(s):  
CHERNET AMENTE ◽  
P. SINGH
Keyword(s):  
Transition Temperature ◽  
Spin Wave ◽  
Wave Scattering ◽  
Diluted Magnetic Semiconductor ◽  
Magnetic Semiconductor ◽  
Ferromagnetic Transition ◽  
Photon Irradiation ◽  
Model Hamiltonian ◽  
Diluted Magnetic ◽  
System Properties

Effects of photo-excitation and spin-wave scattering on magnetization of the diluted magnetic semiconductor (DMS) ( Ga , Mn ) As are theoretically studied. Green function formalism is used to find expression for magnetization and ferromagnetic transition temperature TC starting with a model Hamiltonian consisting of magnons, photons and an interaction of magnons with photons. According to our calculation, there is TC in the absence of magnetic impurity, x = 0, indicating that there could be electronically unpaired influential carriers/holes induced by photon irradiation resulting in residual itinerant band magnetization which can be revealed by experiments. Unusual upturn in magnetization near 0 K temperature values for larger magnon–photon coupling constant is also indicated. Moreover, enhancement of magnetization is established with increase in impurity concentration and even further in the presence of photon–magnon coupling which however decreases due to spin-wave scattering. This leads to the conclusion that at lower temperatures photon irradiation and at higher temperatures spin-wave scattering could affect the system properties predominantly.

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