Assembly of submicrometre ferromagnets in gallium arsenide semiconductors

Abstract

THE discovery of spin-dependent electronic phenomena in magnetic multilayers¹ and granular solids^2,3 has provided valuable insights into the nature of spin interactions in low-dimensional magnetic systems, and has opened the way to new technologies based on these phenomena. In the case of semiconductors, the incorporation of microscopic magnets would allow the electronic flexibility of semiconductor-based quantum structures to be combined with local magnetism⁴, potentially enabling the development of new tunable spin-dependent magneto-electronic and magneto-optical devices. Recent attempts to introduce ferromagnetism into III–V compound semiconductors have involved epitaxial growth of atomically thin layers, yielding two-dimensional magnetic films⁵ rather than localized magnetic structures. Here we describe a simple approach for fabricating discrete microscopic ferromagnets in the III–V semiconductor gallium arsenide. The semiconductor is first uniformly implanted with manganese ions. Subsequent heat treatment leads to a striking phase separation, whereby submicrometre crystals of GaMn nucleate and grow from the implanted layer. The resulting particles are ferromagnetic, with Curie temperatures exceeding room temperature.