Strain-Tunable and carrier-driven structural and magnetic phase transitions in one-dimensional dimerized MoX3 (X=Br, I) atomic chains

The structural, electronic, and magnetic properties of one-dimensional (1D) MoX3 (X=Br,I) atomic chains (ACs), as well as their sensitivity to strain, carrier doping, and optical excitation, were comprehensively investigated using first-principles calculations and the tight-binding approximation. These 1D MoX3 ACs, characterized by alternating Mo-Mo dimers, exhibit semiconducting behavior and a staggered antiferromagnetic (AFM) state, arising from the robust AFM direct exchange. The magnetocrystalline anisotropy energies are 1.079 meV/Mo for MoBr3 and 1.031 meV/Mo for MoI3. Fully noncollinear magnetic calculations reveal that magnetic spirals with helical angles θ=2π/n(n=±2,±3,±4,â,±∞) possess higher energy than the collinear AFM state, confirming the AFM state as the ground state. Under tensile strain, structural transitions occur at 12% for MoBr3 and 6.5% for MoI3, with remarkable superelasticity up to 36% for MoBr3 and 38% for MoI3 before structural failure. Furthermore, carrier doping facilitates an AFM-To-FM phase transition, enabling 100% spin polarization. The lowest energy excitation involves domain walls with an energy of ∼0.17 eV, readily achievable through moderate doping of optically excited electron-hole pairs. These findings provide profound insights into the electronic and magnetic characteristics of 1D MoX3 ACs, highlighting their significant potential for applications in spintronic and wearable flexible electronic devices.