Effect of cation substitution on structural, magnetic and magnetocaloric properties of (La0.7Eu0.3)0.75Sr0.25Mn0.9(Me)0.1O3 (Me = Co, Ti)

Abstract

The paper presents a study of the effect of cation substitution (Co, Ti) → Mn on the structural and magnetic properties, as well as the magnetocaloric effect of the manganite (La0.7Eu0.3)0.75Sr0.25Mn0.9(Me)0.1O3 (Me = Co, Ti). It has been found that both compositions undergo two successive structural phase transitions from the O'-phase (orthorhombic orbitally ordered) to the O-phase (orthorhombic orbitally-disordered) and then to the rhombohedral phase (R-phase) under heating. The difference in the temperature of structural transitions in Co- and Ti-substituted compositions has been accounted for by the competing influence of the steric effect, the charge state, and the specific features of the electronic structure (the Jahn-Teller effect) of cations. The temperature dependence of magnetization reveals that Ti and Co doped compositions exhibit a ferromagnetic (FM) to paramagnetic (PM) transition at TC temperatures of 102 and 165 K, respectively. The correct expression is proposed for the bandwidth W which is proportional to TC. According to the Banerjee criterion, the magnetic phase transitions in (La0.7Eu0.3)0.75Sr0.25Mn0.9(Me)0.1O3 are of the second order. Magnetocaloric effect (MCE) is expanded in the wider temperature range with higher applied magnetic field. For each composition the peak position (Tpeak) of the magnetic entropy change moves to a higher temperature with the increase of magnetic field. Relatively high RCP values are found for both samples.