Atomistic effective Hamiltonian simulations are used to investigate electrocaloric (EC) effects in the lead-free Ba(Zr0.5Ti0.5)O3 (BZT) relaxor ferroelectric. We find that the EC coefficient varies non-monotonically with the field at any temperature, presenting a maximum that can be traced back to the behavior of BZT's polar nanoregions. Below the Burns temperature, this maximum of EC coefficient is demonstrated to be correlated to a very specific microscopic feature. We also introduce a simple Landau-based model that reproduces the EC behavior of BZT as a function of field and temperature, and which is directly applicable to other compounds. Finally, we confirm that, for low temperatures (i.e., in nonergodic conditions), the usual indirect approach to measure the EC response provides an estimate that differs quantitatively from a direct evaluation of the field-induced temperature change [1].
References
[1] Z. Jiang, S. Prokhorenko, S. Prosandeev, Y. Nahas, D. Wang, J. Íñiguez, E. Defay and L. Bellaiche, Phys. Rev. B 96, 014114 (2017).
Acknowledgments
Z.J., S. Prokhorenko, and L.B. are grateful for DARPA Grant No. HR0011-15-2-0038 (MATRIX program) for support. Z.J. also acknowledges support from the NSFC, Grants No. 11574246, No. 1390472, and No. U1537210, National Basic Research Program of China, Grant No. 2015CB654903. S. Prosandeev is supported by ONR Grant No. N00014-12-1-1034, and Grants No. 3.1649.2017/4.6 from RMES, and No. 16-52-0072 Bel_a from RFBR. Y.N. is supported by ARO Grant No. W911NF-16-1-0227. We also acknowledge funding from the LNRF (Grant No. 15/9890527 Greenox, J.Í. and L.B.) and Pearl (Grant No. P12/4853155 Cofermat, J.Í. and E.D.) programs.