Strain relaxation dynamics of multiferroic orthorhombic manganites

M A Carpenter; D Pesquera; D O'Flynn; G Balakrishnan; N Mufti; A A Nugroho; T T M Palstra; M Mihalik Jr; M Mihalik; M Zentková; A Almeida; J Agostinho Moreira; R Vilarinho; D Meier

doi:10.1088/1361-648X/abbdba

Strain relaxation dynamics of multiferroic orthorhombic manganites

J Phys Condens Matter. 2021 Apr 8;33(12). doi: 10.1088/1361-648X/abbdba.

Authors

M A Carpenter¹, D Pesquera¹, D O'Flynn², G Balakrishnan², N Mufti^{3

4}, A A Nugroho³, T T M Palstra³, M Mihalik Jr⁵, M Mihalik⁵, M Zentková⁵, A Almeida⁶, J Agostinho Moreira⁶, R Vilarinho⁶, D Meier⁷

Affiliations

¹ Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, United Kingdom.
² Department of Physics, University of Warwick, Coventry CV4 7AL, United Kingdom.
³ Solid State Chemistry Laboratory, Zernike Institute for Advanced Materials, Rijksuniversiteit Groningen, Nijenborgh 4, 9747AG Groningen, The Netherlands.
⁴ Department of Physics, Universitas Negeri Malang, Jl. Semarang No.5, Malang, 65145 Indonesia, Indonesia.
⁵ Institute of Experimental Physics, Slovak Academy of Sciences, Watsonova 47, Košice, Slovakia.
⁶ IFIMUP, Departamento de Física e Astronomia, Faculdade de Ciências da Universidade do Porto, Rua do Campo Alegre 687, 4169-007 Porto, Portugal.
⁷ Department of Materials Science and Engineering, NTNU Norwegian University of Science and Technology, 7491 Trondheim, Norway.

PMID: 33007773
DOI: 10.1088/1361-648X/abbdba

Abstract

Resonant ultrasound spectroscopy has been used to characterise strain coupling and relaxation behavior associated with magnetic/magnetoelectric phase transitions in GdMnO₃, TbMnO₃and TbMn_0.98Fe_0.02O₃through their influence on elastic/anelastic properties. Acoustic attenuation ahead of the paramagnetic to colinear-sinusoidal incommensurate antiferromagnetic transition at ∼41 K correlates with anomalies in dielectric properties and is interpreted in terms of Debye-like freezing processes. A loss peak at ∼150 K is related to a steep increase in electrical conductivity with a polaron mechanism. The activation energy,E_a, of ≳0.04 eV from a loss peak at ∼80 K is consistent with the existence of a well-defined temperature interval in which the paramagnetic structure is stabilised by local, dynamic correlations of electric and magnetic polarisation that couple with strain and have relaxation times in the vicinity of ∼10^-6s. Comparison with previously published data for Sm_0.6Y_0.4MnO₃confirms that this pattern may be typical for multiferroic orthorhombicRMnO₃perovskites (R= Gd, Tb, Dy). A frequency-dependent loss peak near 10 K observed for TbMnO₃and TbMn_0.98Fe_0.02O₃, but not for GdMnO₃, yieldedE_a⩾ ∼0.002 eV and is interpreted as freezing of some magnetoelastic component of the cycloid structure. Small anomalies in elastic properties associated with the incommensurate and cycloidal magnetic transitions confirm results from thermal expansion data that the magnetic order parameters have weak but significant coupling with strain. Even at strain magnitudes of ∼0.1-1‰, polaron-like strain effects are clearly important in defining the development and evolution of magnetoelectric properties in these materials. Strains associated with the cubic-orthorhombic transition due to the combined Jahn-Teller/octahedral tilting transition in the vicinity of 1500 K are 2-3 orders of magnitude greater. It is inevitable that ferroelastic twin walls due to this transition would have significantly different magnetoelectric properties from homogeneous domains due to magnetoelastic coupling with steep strain gradients.

Keywords: magnetoelastic relaxation; multiferroics; strain coupling.

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