Resonant Magnetic X-ray Diffraction Study on Successive Metamagnetic Transitions in TbB4

Abstract

Resonant magnetic x-ray diffraction experiments on the Shastry–Sutherland lattice TbB 4 were carried out under pulsed magnetic fields up to 30 T at 8 K. TbB 4 exhibits a multi-step magnetization process above 16 T below about 20 K when magnetic fields are applied along the c -axis. We examined the intensity of the 010 magnetic reflection as a function of magnetic field and found that the magnetization plateau phases are accompanied by large XY components of magnetic moments. We propose novel magnetic structures which consist of XY spins and Ising spins for the plateau phases. We also propose that energy level crossing and its inherent degeneracy give rise to the successive metamagnetic transitions in TbB 4 .