Elastic and anelastic anomalies due to spin-state transitions in orthorhombic perovskite from isoelectronic behavior of Co3+ and Fe2+

摘要: Elastic and anelastic anomalies associated with spin-state transitions of Co3+ in NdCoO3 GdCoO3 perovskites the Pnma structure have been investigated using resonant ultrasound spectroscopy (RUS) at high frequencies (0.1–1.5 MHz) dynamic mechanical analysis (DMA) low (0.1–50 Hz). Analysis spontaneous strains related to octahedral tilting calculated lattice parameter data from literature show that sequence changing spin states increasing temperature, → + high-spin intermediate spin, is accompanied by significant variations shear strain due changes ionic radius ions. This implies state/strain coupling, which, turn, leads renormalization modulus. In are small, so coupling weak modulus increases falling temperature a manner scales semi-quantitatively an empirical order parameter. much greater softening up ~35% low-spin field arises through influence both susceptibility. Enhanced acoustic dissipation also observed tentatively attributed mobility transformation twin walls, which likely structures modified local populations. isoelectronic Fe2+ and, although cobaltate silicate not same, large (Mg,Fe)SiO3 pressures suggest effects intermediate-spin transition would be closely analogous those shown GdCoO3. A Fe3+ perovskite similar influence, change its on via Goldschmidt tolerance factor.