Magnetic short-range order and Griffiths-like phase in the S-1/2 spin-dimer ferromagnet BaCu(SeO3)2.

The polycrystals of S = 1/2 spin-dimer compound BaCu(SeO 3) 2 have been synthesized by using solid-state reaction. Without long-range order, the magnetic susceptibility χ (T) curve presents two anomalies at T 1 = 5 K and T G = 58 K due to antiferromagnetic (AFM) short-range order and short-range ferromagnetic (FM) correlations, respectively, which is further supported by the specific heat and electron spin resonance data. The high-temperature χ (T) curve follows the Curie-Weiss law with θ CW = 11.3 K, showing the dominant intradimer FM interaction. The magnetization M (H) curve at 2 K is characteristic of an AFM-FM transition at 0.4 T, suggesting the weak interdimer AFM couplings. The density function theory calculations and quantum Monte Carlo simulations allow an estimation of the intradimer and interdimer exchanges with J 1 / k B = 39.09 K, J 2 / k B = −1.51 K, and J 3 / k B = −1.68 K. Interestingly, the χ −1(T) curve within θ CW < T < T G deviates downward from paramagnetic Curie-Weiss behavior, mimicking the Griffiths-like phase. This is further supported by the ac magnetic susceptibility and magnetic relaxation measurements. The competing intradimer FM and interdimer AFM exchanges with a subtle ratio between them are proposed to be responsible for the formation of Griffiths-like phase. [Display omitted] • Spin-dimer compound BaCu 2 (SeO 3) 2 has been successfully synthesized. • The χ −1(T) curve within θ CW < T < T G deviates downward from PM Curie-Weiss behavior, mimicking the Griffiths-like phase. • The DFT calculations show that the intradimer interaction is FM with J 1 / k B = 39.09 K, the interdimer couplings are weak. • The magnetization reaches 1.06 μ B /Cu2+ at 30 T, very close to the saturated value of 1.08 μ B /Cu2+ (g = 2.15 from ESR). [ABSTRACT FROM AUTHOR]