Enhanced Curie temperature and nonvolatile switching of ferromagnetism in ultrathin (Ga,Mn)As channels

Abstract

The integration of ferroelectric polymer gates on a Mn-doped GaAs magnetic channel provides a promising route for the persistent field-effect control of magnetic properties in high-quality diluted magnetic semiconductors (DMSs) that are otherwise incompatible with traditional oxide ferroelectrics. That control demands the thinnest possible DMS layers, for which to date the Curie temperature (${T}_{C}$) is severely depressed. Here we show that reducing the channel thickness from 7 to 3--4 nm by etching, followed by a brief 135 \ifmmode^\circ\else\textdegree\fi{}C anneal, does not degrade the ${T}_{C}$ (\ensuremath{\sim}70 K) of the 7-nm film. The channel thinning results in a dramatic threefold increase of the ${T}_{C}$ shift controlled by the ferroelectric polarization reversal. Furthermore, we obtain the same exponent $(\ensuremath{\partial}\mathrm{ln} {T}_{C}/\ensuremath{\partial}\mathrm{ln} R)\ensuremath{\equiv}\ensuremath{\gamma}\ensuremath{\approx}\ensuremath{-}0.3$ for all channels with different thicknesses, regardless of the technique used for ${T}_{C}$ determination. These results suggest that the ferromagnetic coupling in an ultrathin 3-nm channel is far from the two-dimensional limit and shows a rather bulklike behavior, similar to well-established 7-nm films.