Abstract
We report the observation of exchange bias in a ferromagnetic Ga0.94Mn0.06As0.77P0.23/ Ga0.94Mn0.06As bilayer, in which the easy axis in one layer is oriented out-of-plane, and in the other in-plane. Magnetization reversal in this system is explored using planar Hall effect (PHE) measurements under various initial conditions and with various field-cooling orientations. Our results show that the two magnetic layers are ferromagnetically exchange-coupled, and that such coupling results in pronounced exchange-bias-like shifts of magnetic hysteresis loops during reversal of in-plane magnetization. The presence of exchange bias in this system can be understood on the basis of magnetic closure domains formed in the layer with the out-of-plane easy axis.
Highlights
Ferromagnetic (FM) films with easy axes normal to the film plane have been extensively studied because of their promise for applications in perpendicular magnetic recording media[1,2]
Measurement of the planar Hall resistance (PHR) in magnetic fields whose direction can be applied along arbitrary in-plane direction provides a convenient tool for investigating the details of magnetization reversal in the layer plane[18,19], and we have adapted this approach for investigating the effects of exchange bias in the Ga0.94Mn0.06As layer[20]
Due to its out-of-plane anisotropy, under in-plane field-cooling conditions, the magnetic structure in Ga0.94Mn0.06As0.77P0.23 layer is expected to occur in multi-domain form comprised of out-of-plane and in-plane configurations that satisfy magnetic flux closure requirements indicated in the figure, similar to that observed in metallic systems involving out-of-plane films[12]
Summary
Suho Choi[1], Seul-Ki Bac[1,2], Xinyu Liu[2], Sanghoon Lee[1], Sining Dong[2], M. We report the observation of exchange bias in a ferromagnetic Ga0.94Mn0.06As0.77P0.23/ Ga0.94Mn0.06As bilayer, in which the easy axis in one layer is oriented out-of-plane, and in the other in-plane Magnetization reversal in this system is explored using planar Hall effect (PHE) measurements under various initial conditions and with various field-cooling orientations. Measurement of the planar Hall resistance (PHR) in magnetic fields whose direction can be applied along arbitrary in-plane direction provides a convenient tool for investigating the details of magnetization reversal in the layer plane[18,19], and we have adapted this approach for investigating the effects of exchange bias in the Ga0.94Mn0.06As layer[20] The angles of magnetization φM, of the applied magnetic field φH, and of the cooling field φHFC are measured counterclockwise from the [110] crystallographic direction in the (001) plane
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