Novel spintronic materials based on ferromagnetic semiconductor chalcopyrites

Abstract

Ternary diamond-like compounds in II-IV-V₂ semiconductor system heavily-doped with transition d-element Mn have been recently prepared. The materials grown in both forms-single crystal layers and polycrystalline bulks-exhibit well defined ferromagnetic hysteresis with a saturation behavior in the magnetization curve up to above room temperature. Curie temperatures are of T_C=310 K to 320 K for (Cd_1−xMn_x)GeP₂ and (Zn_1−xMn_x)GeP₂ compounds. The chemical states in the bulk of ZnGeP₂:Mn and interface of Mn-doped ferromagnetic layer on ZnGeP₂ (001) crystal, have been clarified by electron paramagnetic resonance and in situ photoemission spectroscopy. The as-prepared surface consists of Ge-rich, metallic Mn-compound. In and below the sub-surface region, dilute Mn²⁺ species as precursors of the DMS phase exist. Mn²⁺ions are paramagnetic active on Zn²⁺ sites in the bulk and show five EPR sets of equidistant peaks. Theoretical band-gap calculation suggests a predominant antiferromagnetic order in stoichiometric (Cd, Mn)GeP₂but the systems with vacancies as (Cd, V_C, Mn)GeP₂or (Cd, Ge, Mn)GeP₂ are ferromagnetic and energetically stable. These materials are of great promise for room-temperature spintronics applications.