Co(x nm, x=10nm or 40nm)/Cu(5nm)/Co(2.5nm) layers were deposited between copper electrodes in SiO2 vias. Magnetic states, and the corresponding resistance states, of these devices were switched by electric currents perpendicular to the layers. The I-V loops show asymmetric behavior with hysteresis. When electrons flow in the direction from thick to thin Co layer (positive current), multiple switches were observed on increasing current up to a chosen maximum positive I(write). On decreasing current from I(write), the I-V curve was smooth and characterized by considerably lower resistance. Under reverse current, an abrupt switch to the high resistance state occurred at the current value I(erase)~ -0.9*I(write). Resistance had a maximum at zero current in both states, where the ratio R(high)/R(low) could be as high as factor of four.