Effects of Ho-ion substitution on the magnetic properties of the Ca3Co2O6 frustrated spin-chain compound

The Curie–Weiss temperature θp decreases from a positive value of the x = 0 sample to a negative value of the x = 0.15 sample. This indicates that as the Ho3+ ions increase, the anti-ferromagnetic interaction dominates the ferromagnetic interaction. The effective magnetic moment is also calculated and the result indicates the Ho3+ ions are located at the trigonal prism sites. The variation in the J value also indicates that the intrachain interaction is the dominant ferromagnetic in the x ≤ 0.1 samples and the dominant anti-ferromagnetic for the x = 0.15 sample. Therefore, the current results suggest that the magnetic variation in Ca3Co2O6 with Ho3+ doping is more sensitive than the nonmagnetic Sc3+ ions or low magnetic moment Fe3+ ions doped in high spin trigonal prism Co3+ sites. Based on the results, for a small value of x (x ≤ 0.1), Ho3+ ions limit the magnetic correlation length by breaking the ferromagnetic order along the c-axis, while for a high value of x (x ≥ 0.1), the formation of Ho3+-ions pairs was interpreted. (a) ZFC heating H/M curves for Ca3Co2-xHoxO6 measured in 0.1 T. The solid lines represent Curie–Weiss fits. For x = 0.05–0.15, the H/M values are shifted up by 10, 20, 30 (10−1 T g/emu), respectively. (b) χT vs T curves for Ca3Co2-xHoxO6. For x = 0.05–0.15, the χT values are shifted up by 2, 4, 6 (emu K mol−1 Oe−1), respectively. [Display omitted] •A great sensitivity of the Ca3Co2O6 magnetic behavior to the presence of magnetic foreign cation are emphasized.•As the Ho content increases the ferrimagnetic configuration becomes less stable; and the antiferromagnetic (AFM) interaction enhances gradually.•Antiferromagnetic coupling interaction between Ho3+ ions are interpreted, The complex micro-mechanism are discussed in detail. Ho3+-ion doped spin-chain compounds Ca3Co2-xHoxO6 (x = 0, 0.05, 0.1, 0.15) were prepared by a conventional solid-state reaction method. Rietveld refinement of the X-ray diffraction patterns at room temperature confirmed the rhombohedral structure with the R3¯c space group. The results reveal that the solid solubility of the Ho element in Ca3Co2O6 is in the range of x = 0.1–0.15. Magnetic measurement suggests that with the increased Ho content: (1) the ferromagnetic transition temperature Tc and spin freezing temperature Tƒ decrease obviously; (2) the ferrimagnetic configuration becomes less stable; (3) the dynamic characteristics become slower; and (4) the antiferromagnetic (AFM) interaction enhances gradually. Bas