부산대학교 도서관

Emission [sup.57]Fe Mössbauer spectroscopy (eMS), following the implantation of radioactive [sup.57]Mn[sup.+] ions, has been used to study the temperature dependence of the hyperfine magnetic field at Fe sites in Ba-doped BiFeO[sub.3] (BFO) thin films. [sup.57]Mn β decays (t[sub.1/2] = 90 s) to the 14.4 keV Mössbauer state of [sup.57]Fe, thus allowing online eMS measurements at a selection of sample temperatures during Mn implantation. The eMS measurements were performed on two thin film BFO samples, 88 nm and 300 nm thick, and doped to 15% with Ba ions. The samples were prepared by pulsed laser deposition on SrTiO[sub.3] substrates. X-ray diffraction analyses of the samples showed that the films grew in a tetragonal distorted structure. The Mössbauer spectra of the two films, measured at absorber temperatures in the range 301 K–700 K, comprised a central pair of paramagnetic doublets and a magnetic sextet feature in the wings. The magnetic component was resolved into (i) a component attributed to hyperfine interactions at Fe[sup.3+] ions located in octahedral sites (B[sub.hf]); and (ii) to Fe[sup.3+] ions in implantation induced lattice defects, which were characterized by a distribution of the magnetic field B[sub.Distr]. The hyperfine magnetic field at the Fe probes in the octahedral site has a room temperature value of B[sub.hf] = 44.5(9) T. At higher sample temperatures, the B[sub.hf] becomes much weaker, with the Fe[sup.3+] hyperfine magnetic contribution disappearing above 700 K. Simultaneous analysis of the Ba–BFO eMS spectra shows that the variation of the hyperfine field with temperature follows the Brillouin curve for S = 5/2.
Author(s): Juliana Heiniger-Schell (corresponding author) [1,2,*]; Krish Bharuth-Ram (corresponding author) [3,4,*]; Kimara Naicker [3]; Vusumuzi Masondo [4]; Thien Thanh Dang [2]; Marianela Escobar [2]; Carlos Díaz-Guerra [5]; Georg Marschick [6]; [...]