  According to the Mermin Wagner theorem, two-dimensional material is difficult
to have the Curie temperature above room temperature. By using the method of
band engineering, we design a promising two-dimensional ferromagnetic
semiconductor Cr2XP (X=P, As, Sb) with large magnetization, high Curie
temperature and sizable band gap. The formation of gap is discussed in terms of
the hybridizations, occupation and distribution of electronic states and charge
transfer. Large magnetic moments about 6.16~6.37uB origin from the occupation
of Cr-d electrons in crystal field.Competition and cooperation between d-d
(Cr-d~Cr-d) and d-p-d (Cr-d~X-p~Cr-d) exchange interactions lead to the
emergence of ferromagnetic ordering phase. Furthermore, Curie temperatures,
approaching to 269 K, 332 K and 400 K for Cr2P2, Cr2AsP and Cr2SbP, are
estimated by employing Monte Carlo simulation based on the Heisenberg model.
Magnetic anisotropy energy of Cr2XP is determined by calculating the total
energy dependence on the angle along different directions, and the origin is
also discussed by the second-order perturbation theory. In addition, the Cr2XP
possesses excellent thermodynamical, dynamical and mechanical stabilities, and
can overcome their own gravity to keep their planar structure without the
support of substrate. These above-mentioned advantages will offer some valuable
hints for two-dimensional ferromagnetic semiconductor Cr2XP in spintronic
devices.
