Tóth, Tamás András

The principal aim of this thesis is to gain a better understanding of the competition between magnetic and quadrupolar degrees of freedom on two-dimensional lattices. Recent experimental investigations of the material NiGa2S4 revealed several anomalous properties that might be accounted for within the framework of quadrupolar ordering. Exhibiting b...

飛田, 和男 ヒダ, カズオ Hida, Kazuo Affleck, Ian

The competition between quantum and classical magnetization plateaus of S = 1/2 frustrated Heisenberg chains with modified exchange couplings is investigated. The conventional S = 1/2 frustrated Heisenberg chain is known to exhibit a 3-fold degenerate ↑↓↑ -type classical plateau at 1/3 of the saturation magnetization accompanied by the spontaneous ...

飛田, 和男 ヒダ, カズオ Hida, Kazuo

The S = 1/2 Heisenberg chains with bond alternation and randomness on the strong bonds are studied by the density matrix renormalization group method. It is assumed that the oddth bond is antiferromagnetic with strength J and even-th bond can take the values JA and JF (JA > J > 0 > JF) randomly. The ground state of this model interpolates between t...

飛田, 和男 ヒダ, カズオ Hida, Kazuo

The magnetization process of the S = 1 and 1/2 kagom´e Heisenberg antiferromagnet is studied by means of the numerical exact diagonalization method. It is found that the magnetization curve at zero temperature has a plateau at 1/3 of the full magnetization. In the presence of √3 × √3 lattice distortion, this plateau is enhanced and eventually the f...

飛田, 和男 ヒダ, カズオ Hida, Kazuo

The magnetization process of the S = 1 and 1/2 kagom´e Heisenberg antiferromagnet is studied by means of the numerical exact diagonalization method. It is found that the magnetization curve at zero temperature has a plateau at 1/3 of the full magnetization. In the presence of √3 × √3 lattice distortion, this plateau is enhanced and eventually the f...

飛田, 和男 ヒダ, カズオ Hida, Kazuo

The magnetization process of the S = 1 and 1/2 kagom´e Heisenberg antiferromagnet is studied by means of the numerical exact diagonalization method. It is found that the magnetization curve at zero temperature has a plateau at 1/3 of the full magnetization. In the presence of √3 × √3 lattice distortion, this plateau is enhanced and eventually the f...

飛田, 和男 ヒダ, カズオ Hida, Kazuo

The magnetization process of the S = 1 and 1/2 kagom´e Heisenberg antiferromagnet is studied by means of the numerical exact diagonalization method. It is found that the magnetization curve at zero temperature has a plateau at 1/3 of the full magnetization. In the presence of √3 × √3 lattice distortion, this plateau is enhanced and eventually the f...

飛田, 和男 ヒダ, カズオ Hida, Kazuo

The magnetization process of the S = 1 and 1/2 kagom´e Heisenberg antiferromagnet is studied by means of the numerical exact diagonalization method. It is found that the magnetization curve at zero temperature has a plateau at 1/3 of the full magnetization. In the presence of √3 × √3 lattice distortion, this plateau is enhanced and eventually the f...

飛田, 和男 ヒダ, カズオ Hida, Kazuo

The magnetization process of the S = 1 and 1/2 kagom´e Heisenberg antiferromagnet is studied by means of the numerical exact diagonalization method. It is found that the magnetization curve at zero temperature has a plateau at 1/3 of the full magnetization. In the presence of √3 × √3 lattice distortion, this plateau is enhanced and eventually the f...

飛田, 和男 ヒダ, カズオ Hida, Kazuo

The magnetization process of the S = 1 and 1/2 kagom´e Heisenberg antiferromagnet is studied by means of the numerical exact diagonalization method. It is found that the magnetization curve at zero temperature has a plateau at 1/3 of the full magnetization. In the presence of √3 × √3 lattice distortion, this plateau is enhanced and eventually the f...