High field magnetization of Tm₂AlB₆, an AlB ₂-type analogue compound

The high field magnetization of Tm₂Al¹¹B₆ was measured up to 140 kOe. Tm₂Al¹¹B₆ was previously observed to show an interesting magnetic field dependence wherein one of the two transitions, T_N1, showed little magnetic field dependence from 20 kOe to 70 kOe in the specific heat. A kink in the high field magnetization at ∼3 K is observed even up to 140 kOe, indicating the antiferromagnetic-like nature of the transition, and the high field state's extreme stability (steep phase boundary) versus magnetic field. Even at the highest fields the saturation magnetization takes a small value (∼ 3.3 μ_B/Tm) only about half that expected for a trivalent thulium ion. It is likely that only one Tm ion among the two crystallographic sites in Tm₂Al¹¹B₆ is ordering, while the other has a non magnetic singlet ground state.