Relationship between spontaneous generation of voltage and structural features in a single crystal of Pr0.6Ca0.4MnO3

Spontaneous generation of electrical voltage U was found for the perovskite-like single crystal of Pr0.6Ca0.4MnO3, wherein the charge and orbital orderings occur at T (CO) = 240 K and the antiferromagnetic one occurs at the Neel point T (N) = 174 K. With decreasing the temperature, the U value increases first slowly (in the temperature range of 300 K-T (CO)) and then more rapidly (T (CO)-T (N)). Starting from T (N), U increases exponentially and, at 85 K, reaches the value of 115 mV (in the ab plane) and 6.5 mV (along the c axis). The magnetic field has a different effect on the U value in different temperature ranges: in the temperature range of 85-130 K, it decreases U and, in the range of 130-240 K, increases U. The spontaneous voltage is thought to be caused by the existence of ferromagnetic and charge-orbital-ordered clusters of different topology in the sample. The latter clusters have own features and their structure are described by the non-centrosymmetric space group P2(1) nm.