Width and temperature dependence of lithography-induced magnetic anisotropy in (Ga,Mn)As wires

In-plane magnetic anisotropy of 40-mu m-long (Ga,Mn)As wires with different widths (0.4, 1.0, and 20 mu m) has been investigated between 5 and 75 K by measuring anisotropic magneto-resistance (AMR). The wires show in-plane < 1 0 0 > cubic and [-1 1 0] uniaxial anisotropies, and an additional lithography-induced anisotropy along the wire direction in narrow wires with width of 0.4 and 1.0 mu m. We derive the temperature dependence of the cubic, uniaxial, and lithography-induced anisotropy constants from the results of AMR, and find that a sizable anisotropy can be provided by lithographic means, which allows us to control and detect the magnetization reversal process by choosing the direction of the external magnetic fields. (C) 2009 Elsevier B.V. All rights reserved.