Enhanced and giant low-field magnetocaloric effects in Eu(Ti,Nb,M)O3 (M=Cu or Zn) compounds

For more practical applications, research on magnetic refrigeration has been gradually focused on developing refrigerants with large magnetocaloric effect (MCE) under low magnetic fields (≤2 T). EuTiO3 exhibits considerable low-field MCE near ordering temperature, meanwhile the magnetic switch from antiferromagnetic to ferromagnetic (AFM-FM) in it provides the feasibility of improving the magnetocaloric performance. In this study, a series of Eu(Ti,Nb,M)O3 (M=Cu or Zn) compounds were synthesized, and the crystal structure, magnetic properties together with cryogenic MCEs were investigated in detail. The co-substitution contributes to an FM coupling domination in all the compounds. Besides, significantly enhanced and giant low-field MCEs were detected in these compounds. Under the field change of 1 T, all the samples possess remarkable magnetic entropy change (>15 J·kg-1·K-1) around 5 K without hysteresis. The corresponding refrigerating capacities are calculated to be 68.0, 72.6, 76.0, and 69.6 J·kg-1, respectively, exhibiting an increase of 149–178% than EuTiO3. The outstanding magnetocaloric performances make the Eu(Ti,Nb,M)O3 (M=Cu or Zn) compounds competitive candidates for cryogenic magnetic refrigeration.