Search

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]

Magnetic properties of La 1- x Sr x FeO 3 ( x = 0, 0.1, 0.2, 0.3, 0.4 and 0.5) have been investigated in a wide magnetic field range from 0 to 35 T using pulsed high magnetic field magnetization and electron spin resonance measurements. Experimental results show that both the non-magnetic Sr 2+ dopant and high magnetic fields affect the stability of the robust antiferromagnetic coupling between Fe ions and induce new phase transitions. Especially the phase transition temperatures and hysteresis behavior show a high sensitivity on the Sr dopant and its doping level. On the other hand, a nonlinear Sr doping level dependence of the transition temperatures and hysteresis behavior were observed, indicating that the charge disproportionation is not the sole influence. Thus, in the series Sr doping La 1- x Sr x FeO 3 samples, the dopant induced FeO 6 octahedron distortion and charge disproportionation are coexistence and competition, which leads to a complicated and Sr doping level nonlinearly dependent magnetization behavior. [ABSTRACT FROM AUTHOR]