Ferromagnetic tunneling effect in NiFe/GdO_x/Co and NiFe/AlO_x/Co junctions made by electron beam deposition

Ferromagnetic tunneling effect has been investigated experimentally on the ferromagnetic-ferromagnetic metal junctions with insulator barrier such as 80NiFe/GdO_x/Co and 80NiFe/AlO_x/Co sandwich films fabricated by an electron beam deposition method under various conditions. Results of measurements of magnetization and magnetoresistance for several samples as a function of external magnetic field show the typical behavior for the ferromagnetic tunneling effect. The largest value of magnetoresistance ratio obtained in the present samples is 1.3%. This value is of about one-third compared to that by obtained by Miyazaki et al and far smaller than the theoretically expected value (about 10%). One of the reason of this small value may come from the quality of the barrier.