Mossbauer studies of the Ising spin-glass system Fe0.5Mn0.5TiO3 in connection with the de Almeida-Thouless line

The temperature variation of Mossbauer spectrum of the typical Ising spin-glass Fe0.5Mn0.5TiO3 has been measured in order to investigate the microscopic behavior of spins in relation to the de Almeida-Thouless line. We made the measurements under magnetic fields of 0, 3.2 and 6.4 kOe. We have found that the onset temperature of the magnetic broadening is almost independent of the magnetic fields, although the spin-glass freezing temperature T-SG(H) decreases considerably as the magnetic field increases. We have concluded that the exchange interaction determining the temperature variation of the hyperfine field is not affected by the decrease of T-SG (H).