Synchrotron X-ray imaging of the electron density in RFeO3 (R = Y, Ho) using an APD detector

Structure factors for small hydrothermally grown yttrium and holmium orthoferrites, RFeO(3) (R = Y, Ho), were measured with focused synchrotron radiation at wavelengths of 0.70 and 0.84 A using both scintillation and high-speed avalanche photodiode (APD) detectors. Resulting APD Deltarho images showed striking correlations between aspherical electron densities around Fe and rare-earth metals. Approximate high symmetry in the Deltarho images indicates that cations deform the electron density far more strongly than the O atoms. The Ho-Fe magnetic interactions appear to affect the electron density distribution of the Fe atoms and the magnetic phase transitions. Space group Pnma, orthorhombic, YFeO3 (APD): Mr = 192.76, a = 5.5931 (3), b = 7.6102 (4), c = 5.2806 (3) A, V = 224.77 (2) A(3), Z = 4, Dx = 5.695 Mg m(-3), mu(0.84) = 15.56 mm(-1), F(000) = 356, T = 293 K, R = 0.045, wR = 0.073, S = 4.83 (9) for 1282 unique reflections; HoFeO3 (APD): Mr = 268.78, a = 5.5922 (3), b = 7.6157 (5), c = 5.2798 (3) A, V = 224.86 (2) A(3), Z = 4, D(x) = 7.939 Mg m(-3), mu(0.84) = 61.98 mm(-1), F(000) = 356, T = 293 K, R = 0.036, wR = 0.037, S = 3.07 (6) for 1284 unique reflections.