Renwen Li | Searcharxiv

arXiv2016

Dominant itinerant ferromagnetism in Eu0.5Sr0.5CoO3: evidences from both critical analysis and Rhodes-Wohlfarth's criterion

The critical behaviors of ferromagnet Eu0.5Sr0.5CoO3 arround TC=140.5K have been comprehensively investigated by analyzing a series of isothermal magnetization M(H) curves. Both Modified Arrott plot and Kouvel-Fisher methods give nearly the same critical exponents, which scale nicely the M(H) curves into two different branches below and above TC. The exponents γ=1.044 and δ=3.06 demonstrate the relevance of mean-field characters for this material. The conclusion of mean-field behavior proves a dominant itinerant ferromagnetism (FM) due to a long range exchange interaction in the system. Meanwhile, by using Rhodes-Wohlfarth's criterion [P. Rhodes and E. P. Wohlfarth, Proc. R. Soc. Lond. A 273, 247 (1963)], it is further confirmed that the itinerant FM dominates in the system.

cond-mat.str-el↗

arXiv2011

Spin dynamics in triangular lattice antiferromagnets CuCr$_{1-x}$Mg$_x$O$_2$

The electron spin resonance (ESR) spectroscopy was employed to investigate the spin dynamics in triangular lattice antiferromagnets CuCr$_{1-x}$Mg$_{x}$O$_2$ with $x =$ 0 and 0.02. All spectra can be well fitted by a single Lorentzian lineshape. The analysis of the $g$ factor, the linewidth $\bigtriangleup H$, and the ESR intensity $I$ as a function of temperature suggests the development of significant antiferromagnetic (AFM) spin fluctuations at temperature well above $T_N$ in both samples. However, the evolution of the AFM spin fluctuations is different for each sample. For undoped sample the ESR intensity $I$ is almost temperature independent between $\sim$ 100 K and 50 K and then drops rapidly below 50 K. But for $x =$ 0.02, the $I$ monotonously increases with cooling and reduces rapidly only below $T_N$. These results indicate that the AFM spin fluctuations are extremely strong in the undoped sample and appear to be suppressed upon Mg doping.

cond-mat.str-el↗