Constraints on proximity-induced ferromagnetism in a Dirac semimetal (Cd3As2)/ferromagnetic semiconductor (Ga<…

Breaking time-reversal symmetry in a Dirac semimetal ${\mathrm{Cd}}_{3}{\mathrm{As}}_{2}$ through doping with magnetic ions or by the magnetic proximity effect is expected to cause a transition to other topological phases (such as a Weyl semimetal). To this end, we investigate the possibility of proximity-induced ferromagnetic ordering in epitaxial Dirac semimetal (${\mathrm{Cd}}_{3}{\mathrm{As}}_{2}$)/ferromagnetic semiconductor (${\mathrm{Ga}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x}\mathrm{Sb}$) heterostructures grown by molecular beam epitaxy. We report the comprehensive characterization of these heterostructures using structural probes (atomic force microscopy, x-ray diffraction, scanning transmission electron microscopy), angle-resolved photoemission spectroscopy, electrical magnetotransport, magnetometry, and polarized neutron reflectometry. Measurements of the magnetoresistance and Hall effect in the temperature range 2--20 K show signatures that could be consistent with either a proximity effect or spin-dependent scattering of charge carriers in the ${\mathrm{Cd}}_{3}{\mathrm{As}}_{2}$ channel. Polarized neutron reflectometry sets constraints on the interpretation of the magnetotransport studies by showing that (at least for temperatures above 6 K) any induced magnetization in the ${\mathrm{Cd}}_{3}{\mathrm{As}}_{2}$ itself must be relatively small $(<14\phantom{\rule{0.16em}{0ex}}\mathrm{emu}/{\mathrm{cm}}^{3})$.