Application of Ion Beams to Fabricate and Modify Properties of Dilute Ferromagnetic Semiconductors

Dilute ferromagnetic semiconductors (DFS) have been investigated for more than two decades due to their potentials for spintronics. Mn doped III-V semiconductors have been regarded as the prototype of the type. In this contribution, we will show how ion beams can be utilized in fabricating and modifying DFS. First, ion implantation followed by pulsed laser melting (II-PLM) provides an alternative to low-temperature molecular beam epitaxy (LTMBE) to prepare diverse DFS. The prepared DFSs exhibit pronounced magnetic anisotropy, large X-ray magnetic circular dichroism, anomalous Hall effect and magnetoresistance [1-9]. Going beyond LTMBE, II-PLM is successful to bring two new members, GaMnP and InMnP, into the family of III-Mn-V. Both GaMnP and InMnP show clear signatures of ferromagnetism and an insulating behavior. Second, helium ions can be used to precisely compensate the holes while keeping the Mn concentration constant [10-12].
For a broad range of samples including (Ga,Mn)As and (Ga,Mn)(As,P) with various Mn and P concentrations, we observe a smooth decrease of TC over a wide temperature range with carrier compensation while the conduction is changed from metallic to insulating. We can tune the uniaxial magnetic easy axis of (Ga,Mn)(As,P) from out-of-plane to in-plane with an isotropic-like intermediate state. These materials synthesized or modified by ion beams provide an alternative avenue to understand how carrier-mediated ferromagnetism is influenced by localization.