title: First-order phase transitions in CaFe₂As₂ single crystal: a local probe study.
abstract: (57)Fe Mössbauer spectroscopy has been used to investigate the structural and magnetic phase transitions of CaFe₂As₂ (T(N) = 173 K) single crystals. For this compound we found that V(ZZ) is positive and parallel to the c-axis of the tetragonal structure. For CaFe₂As₂ a magnetic hyperfine field B(hf) was observed at the (57)Fe nucleus below T(N) ~173 K. Analysis of the temperature dependence of B(hf) data using the Bean-Rodbell model shows that the Fe spins undergo a first-order magnetic transition at ~173 K. A collinear antiferromagnetic structure is established below this temperature with the Fe spin lying in the (a, b) plane. Below T(N) the paramagnetic fraction of Fe decreases down to 150 K and for lower temperatures all the Fe spins are magnetically ordered.
authors: Centro Brasileiro de Pesquisas Físicas, Rua Xavier Sigaud 150, Urca, Rio de Janeiro, RJ, Brazil.
authors: M
authors: M
authors: Alzamora
authors: J
authors: J
authors: Munevar
authors: E
authors: E
authors: Baggio-Saitovitch
authors: S L
authors: SL
authors: Bud'ko
authors: Ni
authors: N
authors: Ni
authors: P C
authors: PC
authors: Canfield
authors: D R
authors: DR
authors: Sánchez