Tunable magnetic phase transition and room temperature magnetocaloric effect in La0.67Ba0.33MnO3 nanoparticles

Critical behaviors and the magnetic properties have been investigated in La0.67Ba0.33MnO3 nanoparticles systematically. We found tunable critical behaviors in a ferromagnetic–paramagnetic (FM–PM) transition. Thermal fluctuation induced finite-size effects in the nanoscale thermodynamic systems result in suppression of FM–PM critical transition temperature (TC) and broadening of singularities due to finite-size thermal fluctuation in the nanoscale thermodynamic system. By fitting the critical behaviors with the particle sizes, we confirmed the finite size induced decreasing of TC in La0.67Ba0.33MnO3. Room temperature magnetocaloric effects with enhanced refrigeration efficiency have been found in the La0.67Ba0.33MnO3 nanoparticle systems. A relative cooling power of 205 J/kg is found around room temperature. The broadening of the critical transition and shift of critical temperature in the nanoparticles made them excellent magnetic refrigeration materials near room temperature.