arXiv subjects

Nobuo Furukawa

Publications and source records attributed to Nobuo Furukawa.

77 records · Page 5Linked to original sources

arXiv1995

Temperature Dependence of the Conductivity in (La,Sr)MnO$_3$

Using the Kondo lattice model with classical spins in infinite dimension, conductivity in the perovskite-type $3d$ transition-metal oxide (La,Sr)MnO$_3$ is theoretically studied. Green's functions as well as spontaneous magnetization are obtained exactly on the Bethe lattice as a function of temperature. Conductivity is calculated from the Kubo formula. Below the Curie temperature, resistivity as a function of magnetization is in a good agreement with the experimental data. Anomalous behaviour in the temperature dependence of the optical conductivity observed in (La,Sr)MnO$_3$ is also explained.

cond-mat↗

arXiv1995

Magnetoresistance of the Double-Exchange Model in Infinite Dimension

Double-exchange model in infinite dimension is studied as the strong Hund's coupling limit $J\to\infty$ of the Kondo lattice model. Several quantities such as Green's function and the d.c.\ conductivity are calculated in analytical forms. Magnetoresistance in lightly doped (La,Sr)MnO$_3$ is reproduced very well.

cond-mat↗

arXiv1995

Magnetic and Transport Properties of the Kondo Lattice Model with Ferromagnetic Exchange Coupling

The Kondo lattice model with Hund's ferromagnetic spin coupling is investigated as a microscopic model of the perovskite-type $3d$ manganese oxide (R,A)MnO$_3$ where $R$ and $A$ are rare earth element and alkaline earth element, respectively. We take the classical spin limit $S=\infty$ for the simplicity of the calculation, since the quantum exchange process seems to be irrelevant in the high temperature paramagnetic phase. Magnetic and transport properties of the system are calculated. In the hole doped systems, ferromagnetic instabilities are observed as the temperature is lowered. The giant magnetoresistance of this model is in excellent agreement with the experimental data of (La,Sr)MnO$_3$.

cond-mat↗

arXiv1995

Magnetic Transition Temperature of (La,Sr)MnO$_3$

Using the Kondo lattice model with classical spins in infinite dimension, magnetic phase transition in the perovskite-type $3d$ transition-metal oxide (La,Sr)MnO$_3$ is theoretically studied. On the Bethe lattice, the self-consistency equations are solved exactly. Curie temperatures at the region of double-exchange ferromagnetism $0.1 < x < 0.25$ as well as the Neel temperature at $x=0$ are well reproduced quantitatively. Pressure effect on the Curie temperature is also discussed.

cond-mat↗

arXiv1994

Transport Properties of the Kondo Lattice Model in the Limit $S=\infty$ and $D=\infty$

The Kondo lattice model with Hund's ferromagnetic spin coupling is investigated as a microscopic model of the perovskite-type 3d transition-metal oxide La$_{1-x}$Sr$_x$MnO$_3$. In the classical spin limit $S=\infty$ and the infinite-dimensional limit $D=\infty$, the one-body Green's function is calculated exactly. Transport properties of the system in the presence of magnetic fields are calculated. The giant magnetoresistance of this model, which is in a good agreement with the experimental data of La$_{1-x}$Sr$_x$MnO$_3$, is explained by the spin disorder scattering process.

cond-mat↗