Singularities of magnetic and elastic characteristics of La2/3Ba1/3MnO3: Analysis of martensitic kinetics

Abstract

A coordinated temperature behavior of magnetic susceptibility and internal friction has been observed in the La 2/3 Ba 1/3 MnO 3 manganite in the temperature region of the crystal phase separation 5-340 K. Stepwise temperature behavior of the susceptibility of the single crystal sample and corresponding singular behavior of the internal friction in the polycrystalline manganite have been found. These small-scale features of the temperature dependences of the susceptibility and the internal friction are considered to be a reflection of martensitic kinetics of the structural phase transformation R3c2Imma in the 200 K temperature region. r

Structural first-order transformation in La2/3Ba1/3MnO3: ESR study

“…1, where the positions of the Mn and O ions in the two lattices are shown. The transition between these symmetries is of the first-order type (following the group theory [35]), which was also confirmed experimentally [36,26]. Above 370 K only the rhombohedral R3 c phase was observed according to the neutron diffraction data.…”

Structural phase transition in La2/3Ba1/3MnO3 perovskite: Elastic, magnetic, and lattice anomalies and microscopic mechanism

“…3, where ions are presented. The transition between such symmetries is the 1st order one as based on group theory, 37 our previous studies 14,27,26 and the present ultrasonic and magnetic measurements. The expansion of free-energy density in the powers of the order parameter components Q i for the first order phase transition should be carried out to the terms of the sixth power: [38][39][40][41] …”

“…The specific anomalies of the elastic properties, together with the neutron diffraction and ESR data, 14,26,27 are evident of the martensitic character of the observed structural phase transition, which results in the coexistence of two phases with different crystal structures stabilized by the induced inner strain. The coexisting phases form a microstructure in the substance, which probably represents a sort of "red cabbage" structure.…”

“…19,20 This implies that the transition in La 1−x Sr x MnO 3 has a martensitic nature as well, and so the martensitic transition in La 2/3 Ba 1/3 MnO 3 is not something unique for the perovskite manganites. The La 2/3 Ba 1/3 MnO 3 is ferromagnetic below T C ∼ 340 K, 26 so the structural phase transition R3c↔Imma takes place while the compound is in the ferromagnetic state. It is known that martensitic transitions are very sensitive to different external factors (pressure, applied magnetic fields) and the history of the experiment.…”

“…The La 2/3 Ba 1/3 MnO 3 compound experiences a structural phase transition at T s ∼200 K. 14,26,27 This transition possesses certain features of a martensitic transformation and causes a crystal phase separation in the compound: below room temperature, the compound represents a mixture of the high temperature rhombohedral phase R3c (austenite) and the low temperature orthorhombic phase Imma (martensite). Ultrasonic testing is one of the most widely used techniques for the characterization of perovskites over a wide temperature range.…”