Competing Magnetic phases in Wurtzite Transition-metal Chalcogenides

Antiferromagnetic (AFM) spintronics presents new opportunities for spin-based technologies. Here, we propose a wurtzite family of multiferroic compounds exhibiting competing AFM and altermagnetic phases, where nonrelativistic spin splitting can be switched via ferroelectric polarization. Although wurtzite materials possess strong spontaneous polarization and are attractive for electronic and spintronic applications, only few are known to exhibit both ferroelectric and magnetic properties. Using density-functional theory and atomistic spin models, we examine MnX (X = S, Se, Te) crystals recently stabilized in the wurtzite phase. Contrary to earlier predictions of an altermagnetic ground state of MnSe, our results show all MnX compounds favor a stripe-type AFM ground state, supported by the analysis of the first three nearest-neighbor Heisenberg exchange interactions and the nearest-neighbor biquadratic exchange. We find that the magnetic ground state is tunable by chemical doping, as Cr substitution induces a transition from stripe-type to A-type AFM order, breaking Kramers spin degeneracy and producing altermagnetism. The resulting nonrelativistic spin splitting near the Fermi level is estimated to be 30–200 meV. These findings identify the wurtzite MnX family as a promising platform for electrically controllable AFM states, bridging ferroelectric and spintronic functionalities for future device applications.