Temperature driven transition from giant to tunneling magneto-resistance in Fe3O4/Alq3/Co spin Valve: Role of Verwey transition of Fe3O4

We demonstrate interface energy level engineering, exploiting the modification in energy band structure across Verwey transition temperature (TV) of Fe3O4, in a Fe3O4(111)/Alq3/Co spin-valve (SV). I-V characteristics exhibit a transition in conduction mode from carrier injection to tunneling across TV of Fe3O4 electrode. Both giant magneto-resistance (GMR) and tunneling MR (TMR) have been observed in a single SV, below and above TV, respectively. We have achieved room-temperature SV operation in our device. We believe that the tuning of charge gap at Fermi level across TV resulting in a corresponding tuning of conduction mode and a unique cross over from GMR to TMR.