LATTICE EFFECTS AND MAGNETIC ORDER IN THE CANTED FERROMAGNETIC INSULATOR LA(0.87)5SR(0.125)MNO(3+DELTA)

The structural, magnetic, and transport behavior of orthorhombic, insu lating La0.875Sr0.125MnO3+delta were studied as a function of temperat ure from 20 to 300 g. Upon cooling from room temperature, we observe t he rapid development of a large breathing-mode distortion coincident w ith large positive and negative thermal expansions for the c and b axe s. respectively. The onset of canted ferromagnetic ordering at 220 K i s correlated with the relaxation of this distortion, which reaches val ues similar to those at room temperature when the magnetic ordering sa turates. We observe no first-order-type discontinuity in the volume at the ferromagnetic transition. These results demonstrate a strong coup ling between magnetic ordering and crystal structure even though there is no metal-insulator transition associated with the magnetic transit ion.