abstract
For La(1-x)Pr(x)CoO(3)cobaltites (x = 0, 0.1, 0.2, and 0.3), the dependence of magnetic susceptibility chi(T)is studied in the temperature range 5-400 K. Also, the crystal structure of these cobaltites is investigated, and the effect of pressure up to 2 kbar on their susceptibility is measured atT=78, 150, and 300 K. The specific dependencies chi(T)and the large negative pressure effect are assumed to arise from Co(3+)ions contribution to the total susceptibility evaluated using La(1-x)Pr(x)AlO(3)as a reference system. The obtained experimental data on temperature and pressure effects in magnetism are analyzed within a two-level model with energy gap Delta between the ground state of the system with zero spin of Co(3+)ions and the excited higher-spin state. In this model, magnetism of Co(3+)ions is determined by the temperature-induced population of the excited state, and magnitude of the pressure effect is governed by the volume dependence of Delta. The results of the analysis, supplemented by the theoretical calculations of the electronic structures of LaCoO(3)and PrCoO3, indicate significant increase in Delta with decrease in the unit cell volume both under hydrostatic pressure and by substituting La with Pr having a smaller ionic radius.
keywords
SPIN-STATE TRANSITION; LACOO3; SUSCEPTIBILITY; PARAMAGNETISM; ANOMALIES; BEHAVIOR; PHASE; LA
subject category
Physics
authors
Panfilov, AS; Lyogenkaya, AA; Grechnev, GE; Pashchenko, VA; Vasylechko, LO; Hreb, VM; Kovalevsky, AV
Groups
acknowledgements
A.K. acknowledges the support of the projects CICECO-Aveiro Institute of Materials (ref. UIDB/50011/2020 & UIDP/50011/2020) and POCI-01-0145-FEDER-031875, supported by the COMPETE 2020 Program and National Funds through the FCT/MEC, the Operational Program POCI in its FEDER/FNR component, and the Foundation for Science and Technology, in its State Budget component (OE). L.O.V., V.M.H., G.E.G. and A.S.P. acknowledge the partial support of the Ukrainian Ministry of Education and Sciences under project no. 0118U000264 DB/Feryt.