Magnetic transitions in lattice-matched, ordered FePt_3 based antiferromagnetic/ferromagnetic films

摘要

Measurements of lattice-matched antiferromagnetic/ferromagnetic films which are ideal layered systems to study exchange bias are reported. Epitaxial films of FePt_3 have two kinds of antiferromagnetic ordering. The spin ordering phase with wave vector Q_1 = (1/2 1/2 0) Neel temperature T_N=160 K and that with wave vector Q_2=(1/2 00) has T_N=100 K. Neutron diffraction confirmed the presence of Q_2=(1/2 00) antiferromagnetic ordering in 200 nm Fe_(25)Pt_(75) grown on MgO(100). The loop shift and coercivity of a trilayer film of CoPt_3/FePt_3/CoPt_3 decrease with increasing temperature, consistent with the observed Neel temperature of FePt_3. The x-ray diffraction rocking curve widths of films grown on MgO(100) and Al_2O_3(1120) are compared and related to the loop shifts that are observed in the films with lattice-matched antiferromagnetic/ ferromagnetic interfaces.