. Santa-(n-?-anr,

K. Wang, J. Liu, and Z. Ren, Adv. Phys, vol.58, p.321, 2009.

G. Catalan and J. F. Scott, Adv. Mater, vol.21, p.2463, 2009.

F. Zavalichea, P. Shafer, and R. Ramesh, Appl. Phys. Lett, vol.87, p.182912, 2005.

H. Béa, B. Dupé, S. Fusil, R. Mattana, E. Jacquet et al., Phys. Rev. Lett, vol.102, p.217603, 2009.

R. J. Zeches, M. D. Rossell, J. X. Zhang, A. J. Hatt, Q. He et al., Science, vol.326, p.977, 2009.

, Adv. Mater, vol.25, p.5561, 2013.

A. R. Damodaran, C. Liang, Q. He, C. Peng, L. Chang et al., Adv. Mater, vol.23, p.3170, 2011.

I. C. Infante, S. Lisenkov, B. Dupé, M. Bibes, S. Fusil et al., Phys. Rev. Lett, vol.105, p.57601, 2010.

I. C. Infante, J. Juraszek, S. Fusil, B. Dupé, P. Gemeiner et al., Phys. Rev. Lett, vol.107, p.237601, 2011.

M. Guennou, P. Bouvier, G. S. Chen, B. Dkhil, R. Haumont et al., Phys. Rev. B, vol.84, p.174107, 2011.

Y. Yang, I. C. Infante, B. Dkhil, and L. Bellaiche, Comptes Rendus Physique, vol.16, p.193, 2015.

B. Dupé, I. C. Infante, G. Geneste, P. Janolin, M. Bibes et al., Phys. Rev. B, vol.81, p.144128, 2010.

B. Dupé, S. Prosandeev, G. Geneste, B. Dkhil, and L. Bellaiche, Phys. Rev. Lett, vol.106, p.237601, 2011.

D. Edwards, N. Browne, K. Holsgrove, A. B. Naden, S. O. Sayedaghaee et al., Nanoscale, vol.10, p.17629, 2018.

I. Sosnowska, T. P. Neumaier, and E. Steichele, J. Phys. C Solid State Phys, vol.15, pp.4835-4846, 1982.

D. Rahmedov, D. Wang, J. , and L. Bellaiche, Physical Review Letters, vol.109, p.37207, 2012.

P. Rovillain, R. Sousa, Y. Gallais, A. Sacuto, M. A. Méasson et al., Nat. Mater, vol.9, pp.975-979, 2010.

J. Buhot, C. Toulouse, Y. Gallais, A. Sacuto, R. Sousa et al., Physical Review Letters, vol.115, p.267204, 2015.

D. Sando, A. Agbelele, D. Rahmedov, J. Liu, P. Rovillain et al., Nature Mater, vol.12, pp.641-646, 2013.

S. Lee, M. T. Fernandez-diaz, H. Kimura, Y. Noda, D. T. Adroja et al., Phys. Rev. B, vol.88, p.60103, 2013.

O. Delaire, M. B. Stone, J. Ma, A. Huq, D. Gout et al., Phys. Rev. B, vol.85, p.64405, 2012.

J. A. Schneeloch, Z. Xu, J. Wen, P. M. Gehring, C. Stock et al., Phys. Rev. B, vol.91, p.64301, 2015.

T. Shimizu, T. Era, H. Taniguchi, D. Fu, T. Taniyama et al., Ferroelectrics, vol.403, p.187, 2010.

P. Rovillain, M. Cazayous, Y. Gallais, A. Sacuto, R. P. Lobo et al., Phys. Rev. B, vol.79, p.180411, 2009.

E. P. Smirnova, A. Sotnikov, S. Ktitorov, N. Zaitseva, H. Schmidt et al., Eur. Phys. J. B, vol.83, pp.39-45, 2011.

X. Cao, G. Ji, and X. Jiang, Solid State Communications, vol.245, pp.55-59, 2016.

M. Lejman, G. Vaudel, I. C. Infante, P. Gemeiner, V. Gusev et al., Nature Comm, vol.5, p.4301, 2014.

M. Lejman, G. Vaudel, I. C. Infante, I. Chaban, T. Pezeril et al., Nature Comm, vol.7, p.12345, 2016.

P. Ruello, T. Pezeril, S. Avanesyan, G. Vaudel, V. Gusev et al., Appl. Phys. Lett, vol.100, p.212906, 2012.

S. G. Choi, H. T. Yi, S. Cheong, J. N. Hilfiker, R. France et al., Phys. Rev. B, vol.83, p.100101, 2011.

V. Zelezny, D. Chvostova, L. Pajasova, I. Vrejoiu, and M. , App. Phys. A, vol.100, pp.1217-1220, 2010.

C. Thomsen, H. T. Grahn, H. J. Maris, and J. Tauc, Phys. Rev. B, vol.34, p.4129, 1986.

V. Gusev and P. Ruello, App. Phys. Rev, vol.5, p.31101, 2018.

I. A. Kornev, L. Bellaiche, P. Janolin, B. Dkhil, and E. Suard, Phys. Rev. Lett, vol.97, p.157601, 2006.

I. A. Kornev, S. Lisenkov, R. Haumont, B. Dkhil, and L. Bellaiche, Phys. Rev. Lett, vol.99, p.227602, 2007.

D. Albrecht, S. Lisenkov, W. Ren, D. Rahmedov, I. A. Kornev et al., Phys. Rev. B, vol.81, p.140401, 2010.

S. Prosandeev, D. Wang, W. Ren, J. Íñiguez, and L. Bellaiche, Adv. Func. Mater, vol.23, p.234, 2013.

, The supplementary informations are available online

J. F. Nye, Physical Properties of Crystals, 1985.

P. Marton, A. Klí?, M. Pa?ciak, and J. Hlinka, Phys. Rev. B, vol.96, p.174110, 2017.

S. L. Shang, G. Sheng, Y. Wang, L. Q. Chen, and Z. K. Liu, Phys. Rev. B, vol.80, p.52102, 2009.

E. Borissenko, M. Goffinet, A. Bosak, P. Rovillain, M. Cazayous et al., J. Phys.: Condens. Matter, vol.25, p.102201, 2013.

, The Landau model that is developed is described in the Note III of the Supplementary Informations 38 . This model is partially based on previous work cited in Refs, vol.45, p.46

J. C. Slonczewski and H. Thomas, Phys. Rev. B, vol.1, p.3599, 1970.

M. A. Carpenter and E. K. Salje, Eur. J. Mineral, vol.10, p.683, 1998.

E. K. Salje and M. A. Carpenter, J. Phys.: Condens. Matter, vol.23, p.462202, 2011.

, we provide the detailed expressions of the the longitudinal (vLA) and transverse (vT A) sound velocity as a function of the BiFeO3 grain orientation ? and of the elastic constants Cij, the Supplementary Note IV of the Supplementary Informations, vol.38

W. P. Mason, Physical Acoustics, 1976.

J. Kim, M. Vomir, and J. Bigot, Phys. Rev. Lett, vol.109, p.166601, 2012.

A. V. Scherbakov, A. S. Salasyuk, A. V. Akimov, X. Liu, M. Bombeck et al., Phys. Rev. Lett, vol.105, issue.11, p.117204, 2010.

O. Kovalenko, T. Pezeril, and V. V. Temnov, Phys. Rev. Lett, vol.110, issue.26, p.266602, 2013.

L. Thevenard, C. Gourdon, J. Prieur, H. Jürgen-von-bardeleben, S. Vincent et al.,

. Duquesne, Phys. Rev. B, vol.90, issue.9, p.94401, 2014.

J. Janusonis, T. Jansma, C. L. Chang, Q. Liu, A. Gatilova et al., Sci. Rep, vol.6, p.29143, 2016.