Excitation spectrum and low-temperature thermodynamicsof the Ising-Heisenberg linear ferromagnet

Journal Article · Tue Jul 01 04:00:00 EDT 1980 · Phys. Rev., B: Condens. Matter; (United States)

DOI:https://doi.org/10.1103/PhysRevB.22.251· OSTI ID:5293913

Johnson, J D; Bonner, J C

Important new analytic results have been obtained for the linear, ferromagnetic, spin-1/2, Ising-Heisenberg model in a small magnetic field. Specifically, for zero field an expression, which changes its form at an intermediate value of the variable anisotropy parameter, has been obtained for the thermal excitation energy gap. This special anisotropy value does not correspond to a symmetry change in the Hamiltonian, but is associated with an important difference in the physical significance of the results. For anisotropy greater than the special value, the dominant excitations correspond to bound spin complexes. For anisotropy less than the special value, the dominant excitations are spin waves. These results govern the low-temperature behavior of the specific heat. The effective magnetic excitation gap, which determines the low-temperature susceptibility, is dominated at zero field by the bound states for all anisotropy. More complex crossover effects occur in both specific heat and susceptibility when the analysis is extended to nonzero field. These results may have an important bearing on the quantum soliton problem in the linear ferromagnet.

• Research Organization: Theoretical Division, Los Alamos Scientific Laboratory, Los Alamos, New Mexico 87545
• OSTI ID: 5293913
• Journal Information: Phys. Rev., B: Condens. Matter; (United States), Journal Name: Phys. Rev., B: Condens. Matter; (United States) Vol. 22:1; ISSN PRBMD
• Country of Publication: United States
• Language: English

Related Subjects

656000* -- Condensed Matter Physics
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ANISOTROPY
CRYSTAL MODELS
ENERGY GAP
FERROMAGNETIC MATERIALS
HEISENBERG MODEL
ISING MODEL
MAGNETIC MATERIALS
MAGNETIC PROPERTIES
MAGNETIC SUSCEPTIBILITY
MATERIALS
MATHEMATICAL MODELS
PHYSICAL PROPERTIES
SPECIFIC HEAT
SPIN WAVES
THERMODYNAMIC PROPERTIES