Visualizing Magnetic Domains at Fractional Magnetization Plateaus in a Metallic Shastry-Sutherland Ising-type Rare Earth Tetraboride*

Recently, unconventional magnetic and electronic effects born out of lattice geometric frustration have been observed in metallic frustrated systems. The rare earth tertraboride TmB₄ is one such system with both lattice frustration and itinerant electronic behavior exhibiting complex magnetic phenomena. The Tm ions form a sublattice topologically equivalent to the Shastry-Sutherland lattice in the ab-plane which enters an antiferromagnetic ground state below 11.8 K. Interestingly, the system enters a field-induced ferrimagnetic state at high field, with strong c-axis anisotropy, eventually reaching a field-induced paramagnetic state, exhibiting hysteretic fractional magnetization plateaus along the way, induced by frustration and complex spin flip processes.² Magnetic hysteresis indicates domain formation and the coexistence of fractional magnetization phases. To this end, we report our variable temperature magnetic force microscopy studies on refined floating zone grown TmB₄ single crystals. Various multi-domain patterns were observed at different saturation magnetization plateaus below T_N. The evolution of these magnetic domains at various temperatures and magnetic fields will be presented.