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Title: Giant reversible magnetocaloric effect in the pyrochlore Er 2 Mn 2 O 7 due to a cooperative two-sublattice ferromagnetic order

Most magnetic refrigeration materials showing a large and reversible magnetocaloric effect (MCE) undergo a second-order ferromagnetic (FM) transition involving large-moment magnetic species on one sublattice. Furthermore, a stronger MCE is expected near a cooperative FM order of two or more magnetic species with large magnetic moments residing on different sublattices, but experimental realizations are rare. Here we report on the discovery of large MCE in the cubic pyrochlore Er 2Mn 2O 7 near its second-order FM transition at T c ≈ 34K; under the magnetic field change of 1 and 5 T, the maximum magnetic entropy change –ΔS M is 5.27 and 16.1Jkg –1K –1, and the estimated magnetic refrigerant capacity reaches 68 and 522Jkg –1, respectively. These latter values are among the largest for the known MCE materials. The observed giant and reversible MCE in Er 2Mn 2O 7 is mainly attributed to the large saturation moment of 18.9μ B per formula unit owing to a simultaneous FM ordering of the rear-earth Er 3+ and transition-metal Mn 4+ localized moments. Our results suggest that Er 2Mn 2O 7 pyrochlore is a promising candidate for magnetic refrigeration applications in the temperature range 20–80 K. More importantly, this work provides amore » new material system for developing high-performance MCE materials that can exhibit a strongly coupled FM transition involving two magnetic sublattices of large local moments in a single-phase material.« less
Authors:
 [1] ;  [1] ;  [1] ;  [2] ;  [2] ;  [1] ;  [3] ; ORCiD logo [4] ; ORCiD logo [4] ;  [5] ;  [1]
  1. Chinese Academy of Sciences (CAS), Beijing (China); Univ. of Chinese Academy of Sciences, Beijing (China)
  2. Beijing Institute of Petrochemical Technology, Beijing (China)
  3. Institut Laue Langevin, Grenoble (France)
  4. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  5. Instituto de Ciencia de Materiales de Madrid, Madrid (Spain)
Publication Date:
Grant/Contract Number:
AC05-00OR22725
Type:
Accepted Manuscript
Journal Name:
Physical Review Materials
Additional Journal Information:
Journal Volume: 1; Journal Issue: 6; Journal ID: ISSN 2475-9953
Publisher:
American Physical Society (APS)
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY
OSTI Identifier:
1412041
Alternate Identifier(s):
OSTI ID: 1410587

Cai, Y. Q., Jiao, Y. Y., Cui, Qi, Cai, J. W., Li, Y., Wang, B. S., Fernandez-Diaz, M. T., McGuire, Michael A., Yan, J. -Q., Alonso, J. A., and Cheng, J. -G.. Giant reversible magnetocaloric effect in the pyrochlore Er2Mn2O7 due to a cooperative two-sublattice ferromagnetic order. United States: N. p., Web. doi:10.1103/PhysRevMaterials.1.064408.
Cai, Y. Q., Jiao, Y. Y., Cui, Qi, Cai, J. W., Li, Y., Wang, B. S., Fernandez-Diaz, M. T., McGuire, Michael A., Yan, J. -Q., Alonso, J. A., & Cheng, J. -G.. Giant reversible magnetocaloric effect in the pyrochlore Er2Mn2O7 due to a cooperative two-sublattice ferromagnetic order. United States. doi:10.1103/PhysRevMaterials.1.064408.
Cai, Y. Q., Jiao, Y. Y., Cui, Qi, Cai, J. W., Li, Y., Wang, B. S., Fernandez-Diaz, M. T., McGuire, Michael A., Yan, J. -Q., Alonso, J. A., and Cheng, J. -G.. 2017. "Giant reversible magnetocaloric effect in the pyrochlore Er2Mn2O7 due to a cooperative two-sublattice ferromagnetic order". United States. doi:10.1103/PhysRevMaterials.1.064408.
@article{osti_1412041,
title = {Giant reversible magnetocaloric effect in the pyrochlore Er2Mn2O7 due to a cooperative two-sublattice ferromagnetic order},
author = {Cai, Y. Q. and Jiao, Y. Y. and Cui, Qi and Cai, J. W. and Li, Y. and Wang, B. S. and Fernandez-Diaz, M. T. and McGuire, Michael A. and Yan, J. -Q. and Alonso, J. A. and Cheng, J. -G.},
abstractNote = {Most magnetic refrigeration materials showing a large and reversible magnetocaloric effect (MCE) undergo a second-order ferromagnetic (FM) transition involving large-moment magnetic species on one sublattice. Furthermore, a stronger MCE is expected near a cooperative FM order of two or more magnetic species with large magnetic moments residing on different sublattices, but experimental realizations are rare. Here we report on the discovery of large MCE in the cubic pyrochlore Er2Mn2O7 near its second-order FM transition at Tc ≈ 34K; under the magnetic field change of 1 and 5 T, the maximum magnetic entropy change –ΔSM is 5.27 and 16.1Jkg–1K–1, and the estimated magnetic refrigerant capacity reaches 68 and 522Jkg–1, respectively. These latter values are among the largest for the known MCE materials. The observed giant and reversible MCE in Er2Mn2O7 is mainly attributed to the large saturation moment of 18.9μB per formula unit owing to a simultaneous FM ordering of the rear-earth Er3+ and transition-metal Mn4+ localized moments. Our results suggest that Er2Mn2O7 pyrochlore is a promising candidate for magnetic refrigeration applications in the temperature range 20–80 K. More importantly, this work provides a new material system for developing high-performance MCE materials that can exhibit a strongly coupled FM transition involving two magnetic sublattices of large local moments in a single-phase material.},
doi = {10.1103/PhysRevMaterials.1.064408},
journal = {Physical Review Materials},
number = 6,
volume = 1,
place = {United States},
year = {2017},
month = {11}
}

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