The spontaneous formation of twins in La2/3Ca1/3MnO3 films, at temperatures below about 105K, was observed by using magneto-optical techniques. The twins were revealed as stripes running along <110> directions, where magnetization tilted out of the film plane, due to the stresses in twins. Their appearance was associated with a martensitic phase transition, in the film, which was triggered by a cubic-to-tetragonal transition in the SrTiO3 substrate.

Direct Magneto-Optical Observation of a Structural Phase Transition in Thin Films of Manganites. V.K.Vlasko-Vlasov, Y.K.Lin, D.J.Miller, U.Welp, G.W.Crabtree, V.I.Nikitenko: Physical Review Letters, 2000, 84[10], 2239-42