Exchange anisotropy of (001) oriented Mn1−xPtx/NiFe epitaxial films

Abstract

Exchange anisotropy was investigated for Mn1−xPtx (x=0.06–0.40)/NiFe bilayers prepared by molecular-beam epitaxy on MgO (001) substrates. The bilayers exhibited a large exchange bias field without postannealing, which showed a maximum value of 140–160 Oe around x=0.11. This result is almost the same as those for the (111) oriented bilayers. The exchange anisotropy is induced with the easy direction parallel to the 〈110〉 axes in spite of the fact that the magnetic field is applied along the 〈100〉 direction during the deposition. Diffraction peaks from an ordered phase of Mn3Pt alloy were not observed in the reciprocal space map measured by x-ray diffraction. The origin of the exchange anisotropy is attributed to the antiferromagnetic spin arrangements of the MnPt layer with a disordered face-centered-cubic structure.

Exchange anisotropy of MBE grown Mn1−Pt /NiFe bilayers with (0 0 1) orientation

“…Mn 50 Pt 50 / ferromagnet bilayers are known to exhibit a large bias field H ex [3][4][5][6][7][8]. The results of many works done on Mn 50 Pt 50 /ferromagnet bilayers showed that heat treatment is necessary at around 250 C to obtain a large H ex : On the other hand, Saito et al reported that Mn 90 Pt 10 / NiFe bilayers show a large H ex without heat treatment [9,10].We have reported that Mn 90 Pt 10 /NiFe bilayers with (0 0 1) orientation also show a large H ex ; and the M2H loops measured applying field in the hard direction exhibit a double-shifted loop [11].In this study, we have investigated the behavior of the in-plane anisotropy for (0 0 1) oriented Mn 1Àx Pt x (0.06oxo0.40)/NiFe bilayers varying the direction of the magnetic field applied during the deposition.The Pt(2 nm)/Mn 1Àx Pt x (30 nm)/Ni 80 Fe 20 (5 nm)/ Pt(30 nm)/Cr(10 nm) film were grown by molecular beam epitaxy (MBE) onto MgO(0 0 1) substrates at room temperature. The Mn 1Àx Pt x (0.06oxo0.40) layer was deposited by co-evaporation from Mn and Pt sources and the Ni 80 Fe 20 layer was evaporated from an alloy source.…”

“…We have reported that Mn 90 Pt 10 /NiFe bilayers with (0 0 1) orientation also show a large H ex ; and the M2H loops measured applying field in the hard direction exhibit a double-shifted loop [11].…”

“…In the reciprocal space mapping in (1 0 0) plane, the diffraction peaks from the fundamental face-centered cubic (FCC) of Pt, NiFe, and MnPt were observed [11], but those from the MnPt superlattice were not observed. This implies that the MnPt antiferromagnetic layer has a disordered FCC structure.…”

“…Furthermore, the M2H loop of the hard direction shows the double-shifted loop [11]. To investigate the magnetic anisotropy in detail, the in-plane torque curve was examined.…”

Exchange anisotropy of (001)-oriented Mn80Ir20/NiFe epitaxial bilayers

“…Most of the studies on Mn 50 Pt 50 /ferromagnet and Mn 80 Ir 20 /ferromagnet bilayers have been done with sputtered films but very few have been performed with molecular-beam-epitaxy (MBE) grown bilayers. Thus, we have investigated the [9,10] and (1 1 1) [11] at the substrate temperature T g =room temperature. For (0 0 1)-oriented Mn 89 Pt 11 /NiFe epitaxial bilayers, a large H ex was obtained without heat treatment [9].…”