In ceramics of the composition (BiFe0.9Co0.1O3)0.4-(Bi1/2K1/2TiO3)0.6, novel nano-sized regions called multiferroic clusters (MFC) were found using piezoresponse force microscopy (PFM) and magnetic force microscopy (MFM). The MFC exhibit exceptionally large direct and converse ME coupling, α ≈ 1.0 x 10-5 s/m (dE/dH ≈ 1.3 kV/(cm Oe)) effect which was found locally, using in-situ PFM under magnetic field and MFM in combination with tip induced poling (see Figure 1).
It is assumed that ferrimagnetic order is established in those regions due to higher concentration of Fe and Co as confirmed by secondary ion mass spectrometry (SIMS). At the same time, these regions exhibit a lower concentration of the charge disorder inducing BKT component, which leads to simultaneous long range FE order. The material’s exceptionally large Néel temperature TN = 670 ± 10 K, as found by neutron diffraction, is proposed to be a consequence of ferrimagnetic order in MFC.