A comprehensive study of Heisenberg-like systems with internal spin fluctuation

The magnetic systems described by a two-spin-per-site Heisenberg-like Hamiltonian are investigated in detail. When there are two sub-spins in one site, the magnetic behaviour becomes more complicated than usual Heisenberg systems due to the internal spin fluctuation. Spontaneous magnetization with the variation of temperature is calculated. The quantitative phase diagrams are given for ferromagnetic and antiferromagnetic states and qualitative phase diagrams are shown for mixed states. The roles played by sub-spin quantum number values, four exchange parameters and single-ion anisotropy are studied. The research gives us a comprehensive understanding of the magnetic systems with internal spin fluctuation.

[1]  E. Wang,et al.  Abnormal magnetism and phase transformation of a Heisenberg-like model with internal spin fluctuation , 2002 .

[2]  M. Kriener,et al.  Evidence for a low-spin to intermediate-spin state transition in LaCoO 3 , 2002, cond-mat/0205479.

[3]  Wang Chong-yu,et al.  Investigation of ultra-thin ferromagnetic films with a simple cubic lattice , 2002 .

[4]  Mahmud Tareq Hassan Khan,et al.  Observation of low, intermediate, and high spin states in GdBaCo 2 O 5.45 , 2002 .

[5]  Weiyi Zhang,et al.  Spin states of the Co ion in charge-ordered YBaCo 2 O 5 , 2001 .

[6]  Hua Wu.  Spin state and phase competition in TbBaCo2O5.5 and the lanthanide series LBaCo2O5+δ (0 ≤=δ≤= 1). , 2001, cond-mat/0106374.

[7]  T. Pruschke,et al.  Metal-insulator transition in TlSr 2 CoO 5 from orbital degeneracy and spin disproportionation , 2000, cond-mat/0010239.

[8]  L. P. Shi,et al.  Magnetization reorientation and anisotropy in ultrathin magnetic films , 2000 .

[9]  P. J. Jensen,et al.  Many-body Green's function theory for the magnetic reorientation of thin ferromagnetic films , 2000, cond-mat/0009015.

[10]  K. Asai,et al.  Nuclear-spin relaxation of59Cocorrelated with the spin-state transitions inLaCoO3 , 2000 .

[11]  M. Sakata,et al.  Metal-insulator transition induced by a spin-state transition in TbBaCo 2 O 5 + δ ( δ = 0.5 ) , 2000 .

[12]  Vogt,et al.  Low to high spin-state transition induced by charge ordering in antiferromagnetic YBaCo2O5 , 2000, Physical review letters.

[13]  Q. Jiang,et al.  Effect of single-ion uniaxial anisotropy on the phase diagrams of magnetic system in the presence of internal spin fluctuation , 1999 .

[14]  D. Lederman,et al.  Perpendicular coupling at Fe–FeF2 interfaces , 1998 .

[15]  R. M. Wolf,et al.  Perpendicular Coupling in Exchange-Biased Fe 3 O 4 /CoO Superlattices , 1998 .

[16]  K. Xia,et al.  A comparative study of Heisenberg-like models with and without internal spin fluctuations , 1997 .

[17]  K. Usadel,et al.  Reorientation transition of ultrathin ferromagnetic films , 1997, cond-mat/9701043.

[18]  G. Sawatzky,et al.  Intermediate-spin state and properties of LaCoO3. , 1996, Physical review. B, Condensed matter.

[19]  Moschel,et al.  Reorientation transitions of first and second order in thin ferromagnetic films. , 1995, Physical Review B (Condensed Matter).

[20]  Mark T. Johnson,et al.  Orientational dependence of the exchange biasing in molecular‐beam‐epitaxy‐grown Ni80Fe20/Fe50Mn50 bilayers (invited) , 1994 .

[21]  Moschel,et al.  Influence of the dipole interaction on the direction of the magnetization in thin ferromagnetic films. , 1994, Physical Review B (Condensed Matter).

[22]  Fujimori,et al.  Band-structure and cluster-model calculations of LaCoO3 in the low-spin phase. , 1994, Physical review. B, Condensed matter.

[23]  S. V. Tyablikov.  Methods in the Quantum Theory of Magnetism , 1967 .

[24]  H. Callen,et al.  Statistical Mechanics and Field-Induced Phase Transitions of the Heisenberg Antiferromagnet , 1964 .

[25]  H. Callen.  GREEN FUNCTION THEORY OF FERROMAGNETISM , 1963 .

[26]  D. Haar,et al.  Use of Green Functions in the Theory of Ferromagnetism. I. General Discussion of the Spin-S Case , 1962 .

[27]  D. Haar,et al.  Use of Green Functions in the Theory of Ferromagnetism. II. Dyson Spin Waves , 1962 .