The Magnetocaloric Performance of (Pr,Ca) Manganites Estimated by Magnetic Transition Entropies.

The magnetocaloric applicability of the perovskite-structured (Pr,Ca) manganite family (PCMO) was estimated based on the magnetic transition entropies of polycrystalline bulk samples. Transitions in the temperature range from 5 to 400 K were investigated in external fields up to 5 T. Earlier results published on the matter were reproduced, extended to Ca concentrations below $x = 0.2$ and up to $x = 1$ , and complemented by determining standardized refrigerant capacity estimates corresponding to the largest entropy changes detected in each sample. The quantitative agreement between the measured transition entropies and literature also served to verify a time-optimized data collection method based on quick temperature scans of magnetization at constant magnetic fields. Making use of the mathematical regularity of magnetization curves, improved time, and cryogen efficiency was arguably attained compared with a more traditional data collection method without significant loss of accuracy. The results of this paper convey a very graphical overview of the quite well established phase diagram of PCMO and promise a significant magnetocaloric effect below 150 K, possibly on par with that exhibited by Gd-based alloys around room temperature. However, little hope can be offered for the room temperature refrigeration applications of PCMO. [ABSTRACT FROM AUTHOR]