Absence of magnetic ordering in the ground state of a SrTm2O4 single crystal

We report on the first single crystal study of SrTm 2 O 4 . Magnetization measurements along the crystallographic axes of a nearly stoichiometric Sr 1.07(3) Tm 2.07(6) O 4.00(2) sample show either a positive or a negative Curie-Weiss temperature indicative of a competition between antiferromagnetic and ferromagnetic couplings. The field-dependent magnetization suggests an effective Zeeman splitting of the high-level J -multiplets above ∼8.3 T and that the paramagnetism may originate from only one of the two inequivalent Tm 3+ crystallographic sites. Our single-crystal polarized neutron scattering and powder unpolarized neutron diffraction data show no evidence for either long- or short-range magnetic order even down to ∼65 mK. We reveal two TmO 6 octahedral distortion modes, i.e. , one distortion is stronger than the other especially at low temperatures, which is attributed to different crystal fields of the two inequivalent octahedra. Therefore, the compound SrTm 2 O 4 is unique and different from its brethren in the family of frustrated SrRE 2 O 4 (RE = rare earth) magnets. We propose that crystal field anisotropy may dominate over weak dipolar spin interactions in SrTm 2 O 4 , thereby leading to a virtually non-ordered magnetic state. We report on the first single crystal study of SrTm 2 O 4 .