Magnetic excitations in dicalcium ferrite

Neutron Laue diffraction study of the complex low-temperature magnetic behaviour of brownmillerite-type Ca2Fe2O5

“…In practice, the loss of information due to spherical averaging in NPD data renders diffraction from powder samples unsuitable for determining such subtle effects by structure refinement alone, even with modern diffractometers. Fortunately, a number of experimental studies in the past 20 years have demonstrated the reliability of floatingzone (FZ) growth methods for obtaining large high-quality single crystals of Ca 2 Fe 2 O 5 for use in magnetization and magnetic susceptibility (Maljuk et al, 2003;Marchukov et al, 1993;Zhou & Goodenough, 2005b), Fourier spectroscopy (Brotzeller et al, 1992), and dilatometry (Labii et al, 2013) experiments. However, detailed crystallographic studies have not yet been reported for such crystals below room temperature.…”

Temperature Dependence of the Magnetic and Electric Properties of Ca<sub>2</sub>Fe<sub>2</sub>O<sub>5</sub>

“…There is a decrease of the magnetization with the increase in temperature characteristic of the brownmillerite. The Ca 2 Fe 2 O 5 structure is a weak antiferromagnet directed along the c-axis [27]. This observation shows that the magnetocrystalline anisotropy in the a-c plane is small.…”

“…The little impurity peaks () and () indicate the formation of Fe 3 O 4 [25] and CaO [25] phases respectively were detected in the XRD of the sample (Figure 1). In addition, investigations of magnetic resonance are of special interest, since Ca 2 Fe 2 O 5 is a many-sublattice system with a nontrivial magnetic layer structure [27]. The Figure 2 exhibits the variation of M  with frequency for CF at different temperatures.…”

Order, Disorder, and Dynamics in Brownmillerite Sr2Fe2O5

“…The brownmillerite oxides (A2B2O5, A = alkali earth, B = transition or Group 3 metal) have been widely studied over many decades for their diverse properties, which include fast ionic conductivity [1][2][3][4] , thermoelectricity 5 , catalytic activity [6][7] and complex magnetic ordering [8][9] . The structure is derived from the archetypical cubic perovskite by removal of parallel ⟨110⟩ rows of oxygen atoms to yield alternating layers of BO6 and BO4 units arranged in corner-linked sheets and chains, respectively (Figure 1(a)).…”

“…The brownmillerite oxides ( A 2 B 2 O 5 , A = alkali earth, B = transition or group 3 metal) have been widely studied over many decades for their diverse properties, which include fast ionic conductivity, − thermoelectricity, catalytic activity, , and complex magnetic ordering. , The structure is derived from the archetypical cubic perovskite by removal of parallel ⟨110⟩ rows of oxygen atoms to yield alternating layers of B O 6 and B O 4 units arranged in corner-linked sheets and chains, respectively (Figure a). Oxide-ionic conductivity has been observed and characterized in several brownmillerite phases, though many of these exhibit a sharp increase in conductivity upon conversion to a cubic perovskite phase with disordered oxygen vacancies at high temperatures, ,, suggesting that the best performance may be achieved by suppressing the low-temperature brownmillerite phase.…”