Tunneling magnetoresistance and magnetic properties of Fe-Al2O3 nanogranular films

Tunneling giant magnetoresistance (MR) of the Fe-Al2O3 nanogranular films h as been observed over a wide range of Fe volume fraction x and it took a ma ximum of 4.4% at room temperature for the film with x = 0.45 at H = 10 kOe. Furthermore, the field dependence of MR of the samples is well described b y the form proportional to the square of the magnetization. Moreover, an es timate of the magnetic anisotropy energy density K-u increases with the dec rease of x, yielding a value 2 orders of magnitude greater than the value f or bulk Fe when x = 0.23. The Bloch's law, M-S(T) = M-S0(1-BTb), can also h old for all the samples but with nonbulk parameters dependent on the Fe vol ume fraction. These results reveal a percolation effect on the magnetic pro perties, as well as the conductance, in such nanogranular films. (C) 2001 A merican Institute of Physics.