Dynamic magnetization process of the diluted antiferromagnet RbMncMg1-cF3 in pulse field up to

Abstract In the context of quantum spin dynamics of a two-level system, we study the dynamic magnetization process of dimerized Mn 2+ -Mn 2+ pairs in the diluted antiferromagnet RbMn c Mg 1- c F 3 . Measurements have been performed up to 55 T and lower temperature down to 0.1 K . Magnetization anomalies are associated with successive large and small magnetization steps at specific fields with regular interval. Main steps occur at equally spaced level-crossing fields B n (1⩽ n ⩽5) with a separation of Δ B=6.4 T and subsidiary ones are classified into higher harmonics which fall just in between at the fields B n/2 (1⩽n⩽10) separated by Δ B/2,B n/3 (1⩽n⩽15) separated by Δ B/3,B n/4 (1⩽n⩽20) separated by Δ B /4 and so on when the energy levels have separation with a simple ratio such as (1:1), (1:2), (1:3) and so on. At the lowest temperature, the observed d M /d B curve becomes simpler, suggesting important roles of low-lying excited levels, together with a spin-phonon coupling and a phonon bottleneck effect.