Magnetic phase transitions and magnetocaloric effect in La0.7Ca0.3Mn1-xFexO3 0.00 ≤ x ≤ 0.07 manganites

Abstract

We report a systematic study of the magnetic and magnetocaloric properties of La0.7Ca0.3Mn1-xFexO3, where trivalent Fe is substituted for Mn on the perovskite B-site in the doping range 0.00≤x≤0.07. The polycrystalline materials were prepared by a standard solid state reaction method and X-ray diffraction confirmed that Fe was incorporated without significant structural changes. Magnetic measurements indicate that the ferromagnetic double exchange interaction is weakened with increasing Fe concentration, resulting in a shift in TC from 263 K to 114 K as x varied between 0.00 and 0.07. The large entropy change of 7.7 J/kg K found in the sample with x=0 for a field change of 3 T is initially enhanced to 8.6 J/kg K for x = 0.01, which is likely due to oxygen deficiency. As Fe content increased further, peak entropy values were seen to decline. However, a simultaneous broadening of the ΔSM(T) peaks led to enhanced refrigerant capacity (RC) in the Fe-doped samples of up to 30% over that of La0.7Ca0.3MnO3. Arrott plot analyses and a universal curve method were applied to study the order of the magnetic transition in this system. The incorporation of Fe led to a weakening of first-order nature of the paramagnetic to ferromagnetic transition in La0.7Ca0.3MnO3 and finally initiated a change from first to second order for x > 0.05.

Ferromagnetic–paramagnetic transition temperature in bulk and nanostructured La0.7Sr x Ca0.3−x MnO3 (x = 0.10, 0.15, and 0.20) manganite materials

“…. It is inferred from the reported FM-PM transition temperature of LSCMO, for the same composition x in earlier studies [15,16,19,22,27,44], that the marked anomalous temperature in ultrasonic velocity/attenuation measurements is in agreement with the temperature at which FM-PM phase transition takes place in LSCMO perovskite samples. Therefore, the temperatures of 342, 352, and 359 K, respectively, for BLSCMO10, BLSCMO15, and BLSCMO20 at which a decrease in velocity is observed are the FM-PM phase transition temperatures (T C ) of the respective samples.…”

“…In addition, the LCMO system shows a discontinuous phase transition, which arises due to a strong electron-phonon coupling and/or intrinsic inhomogeneity in the system, giving rise to competing ground state [14,15]. However, LSMO system undergoes a continuous phase transition [16,17].…”

Influence of Sn-doping on Magnetocaloric Properties of La0.7Ca0.3Mn1−xSnxO3(x = 0.0, x = 0.02 and x = 0.04) Compounds

“…Lampen et al (2012) reported the sample La 0.7 Ca 0.3 MnO 3 without any doped, obtained T C of 263 K. Therefore, slight Sn-doped on La 0.7 Ca 0.3 MnO 3 will obtain a significant decrease of larger than 80 K in the Curie temperature compared to La 0.7 Ca 0.3 MnO 3 . In detail, comparing the 2 % Fe-doped result in decreasing T C of 30 K to 2 % Sn-doped result revealed a decrease in the T C of more than 80 K on La 0.7 Ca 0.3 MnO 3.…”

“…Although the Curie temperature decreases as the Sn-doped increased, the magnetic entropy change also increased (Dhahri et al, 2008). Meanwhile, other metals or transition metals will experience a decrease in both Curie temperature and magnetic entropy change as found in Ga-doped (Omri et al, 2012) and Fe-doped conditions (Lampen et al, 2012).…”

“…In detail, comparing the 2 % Fe-doped result in decreasing T C of 30 K to 2 % Sn-doped result revealed a decrease in the T C of more than 80 K on La 0.7 Ca 0.3 MnO 3. Thus, Sn-doped is more effective in decreasing T C when compared to the Fe-doped (Lampen et al, 2012). In order to explore MCE, isothermal magnetic measurements were carried out and the MCE properties of the samples were computed.…”