Anomalous temperature-dependent exchange bias in Fe films deposited on Si substrates with the native oxide layer

The temperature dependence of the exchange bias has been investigated in Fe films deposited on the Si substrates with the native oxidize layer. A crossover from negative to positive exchange bias has been observed with increasing temperature at 30 K, accompanied with the maximum of the coercivity. This effect could be understood as a result of the exchange coupling between the ferromagnetic Fe film and the spin-glasslike Fe oxides particles formed spontaneously at the interface, where the direction of their end spins controls the sign of exchange bias.