Tuning magnetic and magnetocaloric properties around room temperature via chromium substitution in La0.65Nd0.05Ba0.3MnO3 system

In this paper, we report the structural, magnetic and magnetocaloric properties of La0.65Nd0.05Ba0.3Mn1-xCrxO3 (0 <= x <= 0.15) system synthesized by conventional solid-state reaction method. Phase identification is performed by X-ray diffraction analysis, which shows the rhombohedra crystal structure with R -3 c as a space group. Magnetic measurements show that all our samples undergo a second order paramagnetic (PM) - ferromagnetic (FM) transition when the temperature decreases. However, The M(T) shows a decrease in a Curie temperature (T-c) from 330 K for x = 0 to 275 K for x = 0.15 as a Cr ion increases. This decrease can be explained by the decreasing number of hopping electrons, which reduces the double exchange (DE) interaction of Mn3+-O-Mn4+. The role of the trivalent ions Cr3+ is merely to dilute the DE interactions between Mn sites. Moreover, the maximum magnetic entropy change -Delta S-M calculated from the M(mu H-o) measurements are found to be 4.26, 4.03, 3.97 and 3.55 Jkg(-1)K(-1) under an external field change of 5 T for x = 0, 0.05, 0.1 and 0.15, respectively. However, the temperature-averaged entropy change (TEC) over 10 K temperature span under same field, TEC (10 K, 5 T), are 4.19, 3.91, 3.86 and 3.47 Jkg(-1)K(-1). This finding suggests that our samples can be used as a magnetic refrigeration material around room temperature. Furthermore, the Delta S-M-T curves collapse onto a single master curve confirming the second order phase transition. Additionally, a phenomenological universal model is used to predict the magnetocaloric properties for Cr substituted samples.