Magnetic versus nonmagnetic polymorphs of RuBr 3 under pressure
Résumé
Pressure evolution of the crystal structure and magnetism of the honeycomb ��−RuBr3 is studied using high-pressure x-ray diffraction, magnetometry, and density-functional band-structure calculations. Hydrostatic compression transforms antiferromagnetic ��−RuBr3 (��
‾
3
) into paramagnetic ��′−RuBr3 (��
‾
1
) where short Ru-Ru bonds cause magnetism collapse above 1.3 GPa at 0 K and 2.5 GPa at 295 K. Below this critical pressure, the Néel temperature of ��−RuBr3 increases with the slope of 1.8 K/GPa. Pressure tunes ��−RuBr3 away from the Kitaev limit, whereas increased third-neighbor in-plane coupling and interlayer coupling lead to a further stabilization of the collinear zigzag state. Both ��- and ��′−RuBr3 are metastable at ambient pressure, but their transformation into the thermodynamically stable �� polymorph is kinetically hindered at room temperature.