Tuning the magnetic anisotropy via Mn substitution in single crystal Co4Nb2O9

Abstract By using the optical floating-zone technique to grow a series of high-quality Co 4- x Mn x Nb 2 O 9 single crystals, the effect of Mn doping on the magnetic anisotropy and spin-flop is investigated. The antiferromagnetic phase transition and spin-flop transition for these samples ( x  ≤ 3.9) are similar to those in the parent phase of Co 4 Nb 2 O 9 , revealing that Co 2+ ions in Co 4- x Mn x Nb 2 O 9 possess a strong single-ion anisotropy. The critical doping content, above which the magnetic anisotropy changes from easy-plane to easy-axis, has been identified as x  = 3.95 with an additional kink observed in the magnetization curve below the N e el temperature. A spin-flop transition is reported for the first time in Mn 4 Nb 2 O 9 at a field of 10.9 T at 2 K.