Enhancement of ferromagnetism and multiferroicity in Ho doped Fe rich BiFeO3

Crystalline solid solution of BiHoXFe1+XO3 (X=0, 0.05, 0.1, and 0.15) ceramics have been successfully synthesized by slow step sintering schedule. At particular value of X (X=0.1) the sample showed good crystallinity with almost impurity free phases. It was observed that at particular concentration of X (X=0.1), the sample showed enhanced M–H loop by Ho doping in presence of excess Fe. Furthermore, the M–H loop gets reduced with the increase in value of X (X=0.15). Compared to the pure BFO, the dielectric properties for X=0.1 composition are improved due to the decreased oxygen vacancies by the stabilized oxygen octahedron. Raman spectra over the frequency range of 100–1500 cm−1 have been systematically investigated with different concentrations of X. Besides the changes of the peak position and the line width of the all modes, the prominent frequency shift, the line broadening and variation of the intensity for the two-phonon mode between 1270 and 1280 cm−1 were observed with increase in value of X. All these results indicate the existence of strong spin–phonon coupling in Ho doped Fe rich BFO.

► BiHoXFe1+XO3 (X=0.1) sample showed good crystallinity with almost impurity free phases.
► Ferromagnetism for X=0.1 is greatly enhanced by Ho doping with excess Fe.
► K and tan δ value for X=0.1 is improved due to the decrease in oxygen vacancies.
► Higher frequency Raman modes indicate the existence of strong spin–phonon coupling.
► Excess Fe with Ho is expected to act as point defects and promote defect driven ferromagnetism.