Epitaxial growth and exchange biasing of PdMn/Fe bilayers grown by ion-beam sputtering

Epitaxial PdMn/Fe bilayer structures, in both a-axis PdMn(100)/Fe(001)/MgO(001) and c-axis PdMn(001)/Fe(001)/MgO(001) orientations, were grown by ion-beam sputtering. The a-axis samples were grown at low temperatures (T < 280 degreesC) while the c-axis films were stabilized at a higher temperature range (T > 300 degreesC). Vibrating sample magnetometry measurements show that the as-grown a-axis samples do not have a measurable exchange bias while c-axis samples have an exchange bias field H-e similar to 33 Oe. However, annealing at 230 degreesC for 40 min results in a measurable exchange (H-e similar to 10 Oe) for a-axis samples due to chemical ordering. The possible cause for the difference of H-e in a-axis and c-axis orientations is also discussed. In addition to the normal structure, inverted structures were obtained epitaxially. The exchange biasing for Fe(001)/PdMn(001)/MgO(001) is as big as 68 Oe. (C) 2001 American Institute of Physics.