Influence of the anisotropy and of the external tension in the phase transitions of antiferromagnets showing spin-flop
Description
A model where it is considered: (a) a localized spin 1/2 system; (b) antiferromagnetic interaction, anisotropic, among spins via coupling constant (exchange); (c) first-neighbour interactions only; (d) external magnetic field parallel to the easy axis; (e) coupling constant dependent of lattice dislocations; (f) elastic contributions introduced at thermodynamic level. The existence of the paramagnetic (PM), antiferromagnetic (AF) and spin-flop (SF) phases is detected. In the space temperature, external magnetic field and external tension emerges a critical surface which separate the ordered phases (also separated by a critical surface) of the disordered ones. The modifications in the phase diagrams resulting of the anisotropy variation are studied, at fixed volume. The behaviour of the system in relation to the external tension variation is analized. The transition orders for each one of the cases are determined. (L.C.)
Availability note (English)
Available CBPF, Brazil.Abstract (Portuguese)
Analisa-se um modelo onde considera-se: (a) um sistema de spins 1/2, localizados; (b) interacao antiferromagnetica, anisotropia, entre spins via constante de acoplamento (exchange); (c) interacoes somente entre primeiros vizinhos; (d) campo magnetico externo paralelo ao eixo facil; (e) constante de acoplamento dependente das deslocacoes da rede; (σ) contribuicoes elasticas introduzidas a nivel termodinamico. E detectada a existencia das fases paramagnetica (PM), antiferromagnetica (AF), e spin-flop (SF). No espaco temperatura, campo magnetico externo e tensao externa aparece uma superficie critica que separa as fases ordenadas (tambem separadas por uma superficie critica) da fase desordenada. Estudam-se, a volume fixo, as modificacoes no diagrama de fases em decorrencia da variacao da anisotropia. Analisa-se o comportamento do sistema em relacao a variacao da tensao externa. Determina-se a ordem das transicoes para cada um dos casos. (Autor)Additional details
Additional titles
- Original title (Portuguese)
- Influencia da anisotropia e da tensao externa nas transicoes de fase de antiferromagnetos apresentando spin-flop
Publishing Information
- Imprint Pagination
- 162 p.
INIS
- Country of Publication
- Brazil
- Country of Input or Organization
- Brazil
- INIS RN
- 15070870
- Subject category
- S75: CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY;
- Resource subtype / Literary indicator
- Numerical Data, Thesis, Non-conventional Literature
- Descriptors DEI
- ANISOTROPY; ANTIFERROMAGNETIC MATERIALS; COMPILED DATA; COUPLING CONSTANTS; MAGNETIC FIELDS; PHASE DIAGRAMS; PHASE TRANSFORMATIONS; SPIN; THEORETICAL DATA
- Descriptors DEC
- ANGULAR MOMENTUM; DATA; DIAGRAMS; INFORMATION; MAGNETIC MATERIALS; MATERIALS; NUMERICAL DATA; PARTICLE PROPERTIES