Bach Thanh Cong

The concentration dependence of the Curie temperature of the colossal magnetoresistance perovskite La1-xCaxMnO3

Abstract The concentration dependence of the Curie temperature of the colossal magnetoresistance perovskite La 1− x Ca x MnO 3 is explained using a phenomenological model for interacting electronic and magnetic-phase transitions.

Theory for long range magnetic order in nanometer films

The functional integral method and Heisenberg model for localised spins were used for the calculation of the thermodynamics characteristics of magnetic films. It was shown in the Gaussian approximation that the Curie temperature is strongly reduced when the films thickness reduces to the nanometer region.

Tunnelling magnetoresistance in nanometer granular perovskite systems

In this contribution the phenomenological theory for the tunnelling magnetoresistance phenomenon observed in granular perovskite manganese systems is developed using Landauer ballistic transport concept. It was shown that the field dependence, magnitude and derivative of magnetoresistance ratio observed experimentally are well reproduced by the presented theory.

Study on Lattice and Electronic Structures at the Surface of BaTiO 3 Thin Films by DFT Method

In this paper, the density functional theory (DFT) study on nano-thin lms of the most typical ferroelectric compound BaTiO3 was presented. The results showed that the convergence of the lm model using for DFT calculation were obtained for the thickness of the vacuum slabs as large as ten times of the BaTiO3 slabs within the total energy error v 0.01 eV. The lattice contraction was observed in the surface region of the material. The dierence in atomic layer termination, between BaO terminated and TiO2 terminated lms, gives rise to the dierence in lattice reconstruction at the surface region which, in turn, leads to the dierence in surface electric dipoles. The surface eect acts on the electronic structure of thin lms in the manner of the asymmetry of atomic sites and the structural reconstruction due to the surface relaxation. Our results indicated that the termination also decides how and how much these two manners take eects on the electronic structure of the material.