Magnetic domain structure and possible low-temperature structural transition in La_0.78Ca_0.22MnO₃ single crystals

Spontaneous ferromagnetic domain structure in La_0.78Ca_0.22MnO₃ single crystals has been investigated by means of magneto-optical technique. The magnetic domain topology was found to be correlated with the intrinsic twin structure of the investigated crystal. With decreasing temperature the regular network of ferromagnetic domains undergoes significant changes resulting in apparent rotation of the domain walls in the temperature range of 70-150 K. The observed modifications of the domain structure are reversible and the original domain structure can be restored upon heating. The rotation of the domain walls is interpreted in terms of additional twinning of the crystals resulting from the possible low-temperature Jahn-Teller (JT) distortion of the orthorhombic cell.