  Reconfigurable magnetic tunnel diodes and transistors are a new concept in
spintronics. The realization of such a device requires the use of materials
with unique spin-dependent electronic properties such as half-metallic magnets
(HMMs) and spin-gapless semiconductors (SGSs). Quaternary Heusler compounds
offer a unique platform to design within the same family of compounds HMMs and
SGSs with similar lattice constants to make coherent growth of the consecutive
spacers of the device possible. Employing state-of-the-art first-principles
calculations, we scan the quaternary Heusler compounds and identify suitable
candidates for these spintronic devices combining the desirable properties: (i)
HMMs with sizable energy gap or SGSs with spin gaps both below and above the
Fermi level, (ii) high Curie temperature, (iii) convex hull energy distance
less than 0.20 eV, and (iv) negative formation energies. Our results pave the
way for the experimental realization of the proposed magnetic tunnel diodes and
transistors.
