First-Principles Combinatorial Design of Transition Temperatures in Multicomponent Systems: The Case of Mn in GaAs

Abstract

The transition temperature TC of multicomponent systems--ferromagnetic, superconducting, or ferroelectric--depends strongly on the atomic arrangement, but an exhaustive search of all configurations for those that optimize TC is difficult, due to the astronomically large number of possibilities. Here we address this problem by parametrizing the TC of a set of approximately 50 input configurations, calculated from first principles, in terms of configuration variables ("cluster expansion"). Once established, this expansion allows us to search almost effortlessly the transition temperature of arbitrary configurations. We apply this approach to search for the configuration of Mn dopants in GaAs having the highest ferromagnetic Curie temperature. Our general approach of cluster expanding physical properties opens the way to design based on exploring a large space of configurations.

Research Update: Towards designed functionalities in oxide-based electronic materials

“…Under such constraints, configurational search optimization techniques (such as genetic algorithms) are used to search for the atomic configurations that satisfy the targeted function by on-the-fly calculation of properties 24,[31][32][33] or via a surrogate model such as cluster expansion. 34,35 Good optimization methods find the optimal configurations by sampling only a tiny fraction of the configurational space-typically, a couple of thousands when the size of the space is 10 14 -10 20 .…”

Surface treatments and magnetic properties of Ga1−xMnxAs thin films

“…In recent times a Curie temperature as high as 250 K [2] was obtained with delta-doped samples and moreover it was predicted [3] that carefully designed layered structure could have T c up to 350 K. Efficient spin injection was proved to be effective in a (Ga,Mn)As based heterostructure [4] and current driven magnetization reversal was also realized [5]. These advances are not supported by a similar knowledge on (Ga,Mn)As surface, which still lacks reliable cleaning and preparation protocols to obtain pure and ordered surfaces.…”

Equilibrium Macroscopic Structure Revisited from Spatial Constraint

“…Although quantitative estimations of the macroscopic structures in equilibrium state have been amply performed by a variety of theoretical studies, [7][8][9][10][11][12][13] the role of the spatial constraints on equilibrium properties does not get sufficient attention so far. It is thus highly expected that there remains hidden universally in equilibrium macroscopic structures, which reflect the spatial constraints.…”