Spin-glass transition in single-crystal BiFeO3

Magnetic properties of BiFeO3 (BFO) single crystals with rhombohedral symmetry (R3c) were measured in the temperature range of 4.2-350 K. Zero field cooled (ZFC) and field cooled magnetization curves split below 250 K with a sharp cusp around 50 K in the ZFC curves revealing spin-glass behavior in BFO single crystals. The observed coercive field increases with decreasing temperature, suggesting week ferromagnetism below similar to 10 K and spin glass behavior below similar to 120 K. The cusps around the freezing temperature [T-f(omega)] which are frequency dependent confirm the spin-glass behavior in BFO single crystals with spin freezing temperature (T-SG=29.4 +/- 0.2 K). The critical exponent z nu=1.38 agrees rather well with experimental values in LaMn0.5Fe0.5O3 (z nu=1.0) [K. De , J. Appl. Phys. 99, 13908 (2006)] and the mean field theory (z nu=2.0) of Kirkpatrick and Sherrington [Phys. Rev. B 17, 4384 (1970)].