Compositional dependence of the magnetocaloric effect inLa1−xCaxMnO3

A detailed investigation of the thermodynamic properties of ${\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{Ca}}_{x}\mathrm{Mn}{\mathrm{O}}_{3}\phantom{\rule{0.3em}{0ex}}(0\ensuremath{\leqslant}x\ensuremath{\leqslant}0.52)$ for possible applications in magnetic refrigeration is presented. The adiabatic magnetic entropy change $\ensuremath{\mid}\ensuremath{\Delta}S\ensuremath{\mid}$ is determined for a $2\phantom{\rule{0.3em}{0ex}}\text{Tesla}$ change in magnetic field using magnetization measurements. A broad double peak behavior as a function of $x$ is observed with maximum absolute values ${\ensuremath{\mid}\ensuremath{\Delta}S\ensuremath{\mid}}_{\mathrm{max}}$ near $5.5\phantom{\rule{0.3em}{0ex}}\mathrm{J}∕\mathrm{kg}\phantom{\rule{0.2em}{0ex}}\mathrm{K}$ for $x\ensuremath{\approx}0.28$. The largest ${\ensuremath{\mid}\ensuremath{\Delta}S\ensuremath{\mid}}_{\mathrm{max}}$ values do not coincide with the maximum value of the ferromagnetic transition temperature ${T}_{c}$. The relatively large adiabatic magnetic entropy change is moderated by a large heat capacity, which leads to a modest adiabatic temperature change of about $2\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ for the $x=0.28$ specimen. The largest contribution to ${\ensuremath{\mid}\ensuremath{\Delta}S\ensuremath{\mid}}_{\mathrm{max}}$ occurs for magnetic field changes in the range $0\ensuremath{\leqslant}H\ensuremath{\leqslant}2\phantom{\rule{0.3em}{0ex}}\text{Tesla}$; increasing the magnetic field range to $3\phantom{\rule{0.3em}{0ex}}\text{Tesla}$ only increases ${\ensuremath{\mid}\ensuremath{\Delta}S\ensuremath{\mid}}_{\mathrm{max}}$ by about 20%.