Spontaneous chemical ordering and exchange bias in epitaxial Mn0.52Pd0.48/Fe(001) bilayers prepared at room temperature

We report spontaneous chemical ordering of Mn0.52Pd0.48 films, grown by molecular-beam epitaxy on body-centered-cubic Fe(001) films. The bilayers were grown at room temperature onto a seeding structure of Ag(001)/Fe(001)/GaAs(001). X-ray, neutron, and electron diffraction studies confirm extensive chemical ordering of the MnPd to the L1(0) antiferromagnetic phase which grows as a twinned film with the tetragonal c axis in the film plane. The Fe film exhibits a unidirectional exchange bias and we find no pronounced difference in magnetic structure of the biased Fe layer at the ascending and descending crossing fields where the net moment along the applied field axis is zero. (C) 2002 American Institute of Physics.