Magnetic anisotropy of ferromagnetic Ga_1-xMn_xAs formed by Mn ion implantation and pulsed-laser melting

We measured the magnetic anisotropy of nearly fully relaxed ferromagnetic Ga_1-xMn_xAs formed by Mn ion implantation followed by pulsed-laser melting (II-PLM) using magnetometry and ferromagnetic resonance. In qualitative terms the material formed by II-PLM exhibits all magnetic anisotropy features commonly found in Ga_1-xMn_xAs films fabricated by low-temperature molecular beam epitaxy (LT-MBE). Quantitatively, however, the magnetic anisotropy of II-PLM Ga_1-xMn_xAs is dominated by cubic anisotropy terms, which we attribute to the smaller strain in the II-PLM material due to the absence of Mn interstitials. One should note, however, that II-PLM Ga_1-xMn_xAs also exhibits a weak but finite uniaxial in-plane magnetic anisotropy similar to that observed in LT-MBE Ga_1-xMn_xAs, which can be ascribed to the small built-in compressive strain. The similarity between II-PLM and LT-MBE Ga_1-xMn_xAs clearly points to an intrinsic origin of this property, independent of the method of fabrication. At low temperatures the remnant in-plane magnetization of the II-PLM film exhibits single-domain characteristics, while perpendicular magnetization shows a multiple-domain behavior. © 2008 American Institute of Physics.