M.Y. Ruan

Spin-glass-like freezing in spin-chain compounds Ca3Co2−xMnxO6: Effect of disorder

We have illustrated the presence of spin-glass-like freezing in the Mn-doped spin-chain compounds Ca3Co2−xMnxO6, which was not reported previously. With increasing Mn composition, the magnetic relaxation due to spin freezing is gradually suppressed. Interestingly, the magnetization in the intermediate Mn compositions relaxes more slowly (characteristic time is significantly enhanced) than those in x = 0.0 and 1.0. This could be understood within the framework of disorder with randomness or imperfections, which plays an important role in the formation of spin-glass-like feature in intermediate Mn compositions, quite different from the cases in x = 0.0 with strong spin frustration and in x ∼ 1.0 with perfect Co/Mn ionic order.

Effect of nonmagnetic Sc ion on the intrachain coupling in spin-chain compounds Ca3Co2−xScxO6

We have demonstrated that in Ca3Co2−xScxO6, substitution of nonmagnetic Sc3+ (S = 0) for high-spin Cotrig, even up to the solid solubility limit of x = 0.5−0.6, does not dramatically modify the intrachain ferromagnetic (FM) interaction. This is quite different from the cases of Ir- and Rh-doping, which much enhance the intrachain FM interaction, and the cases of Mn-, Fe-, and Cr-doping, which gradually reduce the intrachain FM interaction, simultaneously introducing antiferromagnetic interaction. The results of band-structure calculations of x = 0.5 are qualitatively consistent with our magnetization data.

Antiferromagnetic ordering in spin-chain multiferroic Gd2BaNiO5 studied by electronic spin resonance

High-field electron spin resonance (ESR) has been employed to study the antiferromagnetic (AFM) ordering state (T < TN = 55 K) of spin-chain multiferroic Gd2BaNiO5. The spin reorientation at TSR = 24 K is well characterized by the temperature-dependent ESR spectra. The magnetization data evidence a field-induced spin-flop transition at 2 K. The frequency-field relationship of the ESR data can be explained by conventional AFM resonance theory with uniaxial anisotropy, in good agreement with magnetization data. Related discussion on zero-field spin gap is presented.