Behavior of Clustered State above the Curie Temperature in La0.78Ca0.22MnO3 Single Crystal
The results of structural neutron diffraction study and the data on the transport and magnetic properties (the linear and nonlinear (second and third order) susceptibilities) are presented for the La0.88Ca0.22MnO3 single crystal. This compound has the orthorhombic Pbnm space group, showing no structural transformations between 90 K and 300 K. It exhibits the paramagnet-ferromagnet (P-F) (TC 186 K) and insulator – metal (I-M) (ТIM 201 K > TC) phase transitions. The measurements of the second harmonic of the magnetization in the parallel ac and dc H magnetic fields, M2(H,T), showed that below T* 252 K, the FM clusters appear in the PI matrix undergoing the second-order transition. The concentration of the FM clusters increases with cooling so that it is above the percolative threshold value below TIM, and the sample exhibits metallic behavior. The M2(H) hysteresis loops possess a high sensitivity to the I-M transition. Their usual central symmetry is broken in the vicinity of TIM and the loops become asymmetric. This effect is attributed to cluster link nucleation-and-growth process.
V.A. Ryzhov et al., "Behavior of Clustered State above the Curie Temperature in La0.78Ca0.22MnO3 Single Crystal", Solid State Phenomena, Vols. 168-169, pp. 485-488, 2011