The observed topological vortex domains and the rotating magnetocaloric effect in the hexagonal R MnO 3( R= Ho, Er, and Yb) crystals

Hexagonal RMnO3 (R = Er, Ho and Yb) single crystals were grown and their unique vortex domain structures, magnetic properties and magnetocaloric effect (MCE) were comprehensively investigated. The topological vortex domains/structures were clearly illustrated by polarized optical microscope and piezo response force microscopy, confirming a high quality of the crystals. The magnetic transitions related to R3+-Mn3+ interactions and anisotropic properties were observed in the RMnO3 crystals. The broad peaks of magnetic entropy change -SM appeared around T_N^R revealed that the order of R3+ moments is crucial to the large MCE. A giant rotating MCE (RMCE: ~10.57 J/kg K) was obtained with magnetic field changing from 0 to 50 kOe in ErMnO3, accompanied with a large refrigerant capacity (RC: ~159 J/kg). These significant RMCE and RC behaviors are found to be closely related to the R3+-R3+, and R3+-Mn3+ interactions in these RMnO3. These results may open up a possibility for designing low-temperature magnetic cooling devices by tailoring the R-4f and Mn-3d orbit interactions.