We report the structure and magnetic properties of Co-doped TmMnO3 polycrystals for Co doping levels of 0≤x≤0.9. TmMnO3 (x=0) prepared at ambient pressure was hexagonal.Hexagonal and orthorhombic phases coexisted in TmMn1-xCoxO3 for 0≤x<0.5. We obtained almost single-phase orthorhombic samples with 0.5≤x≤0.9 using complex polymerization.Ferromagnetic orthorhombic TmMn1-xCoxO3 formed upon Co doping. The ionic states of Tm, Mn, and Co were determined through magnetization measurements. The rapid decrease in magnetization for 0.5≤x≤0.7 below about 25 K was explained using a model consisting of a combination of ferromagnetic Mn-Co and paramagnetic Tm sublattices.

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