Magnetic Transitions in Lattice-matched, Ordered FePt₃ Based Antiferromagnetic/Ferromagnetic Films

Abstract

Measurements of lattice-matched antiferromagnetic/ferromagnetic films which are ideal layered systems to study exchange bias are reported. Epitaxial films of FePt₃ have two kinds of antiferromagnetic ordering. The spin ordering phase with wave vector Q₁=(½ ½ 0) has a Néel temperature T_N=160 K and that with wave vector Q₂=(½ 0 0) has T_N=100K. Neutron diffraction confirmed the presence of Q₂=(½ 0 0) antiferromagnetic ordering in 200 nm Fe₂₅Pt₇₅ grown on MgO(100). The loop shift and coercivity of a trilayer film of CoPt₃ ∕ FePt₃ ∕ CoPt₃ decrease with increasing temperature, consistent with the observed Néel temperature of FePt₃. The x-ray diffraction rocking curve widths of films grown on MgO(100) and Al₂O₃(112̲0) are compared and related to the loop shifts that are observed in the films with lattice-matched antiferromagnetic/ferromagnetic interfaces.