Magnetic anisotropy in an oxo-centered {Mn₃O}-type spin triangle

We report the results of experimental and theoretical studies on the magnetic properties of one of the trinuclear oxo-centered Mn complexes, Mn ₃O-(1) (Compound 1 in Ref. [1]), where three identical Mn ³⁺(S = 2) ions form a nearly equilateral triangle. The magnetic susceptibility χ measured using a SQUID magnetometer from room temperature down to 1.8 K shows a typical behavior for an antiferromagnetic (AFM) spin ring with a ground spin state S_T = 0, whereby _χT decreases gradually as temperature decreases. A stepwise magnetization with very broad steps centered at H ≈ 13 T and H ≥ 32 T is observed in a pulsed-field magnet experiment up to 33 T at T = 1.7 K. From a numerical calculation using a model Hamiltonian, we find that the magnetic properties of the subject compound are well characterized by isosceles-type AFM exchange constants, J ≡ J₁₂ = J₁₃ = -31.7 K and J′ ≡ J₂₃ = -35.9 K, and by a single ion anisotropy, D = 11.1 K.