arXiv subjects

Zhe Qu

Publications and source records attributed to Zhe Qu.

57 records · Page 4Linked to original sources

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↗

arXiv2009

Complex electronic states in double layered ruthenates (Sr1-xCax)3Ru2O7

The magnetic ground state of (Sr$_{1-x}$Ca$_x$)$_3$Ru$_2$O$_7$ (0 $\leq x \leq$ 1) is complex, ranging from an itinerant metamagnetic state (0 $\leq x <$ 0.08), to an unusual heavy-mass, nearly ferromagnetic (FM) state (0.08 $< x <$ 0.4), and finally to an antiferromagnetic (AFM) state (0.4 $\leq x \leq$ 1). In this report we elucidate the electronic properties for these magnetic states, and show that the electronic and magnetic properties are strongly coupled in this system. The electronic ground state evolves from an AFM quasi-two-dimensional metal for $x =$ 1.0, to an Anderson localized state for $0.4 \leq x < 1.0$ (the AFM region). When the magnetic state undergoes a transition from the AFM to the nearly FM state, the electronic ground state switches to a weakly localized state induced by magnetic scattering for $0.25 \leq x < 0.4$, and then to a magnetic metallic state with the in-plane resistivity $ρ_{ab} \propto T^α$ ($α>$ 2) for $0.08 < x < 0.25$. The system eventually transforms into a Fermi liquid ground state when the magnetic ground state enters the itinerant metamagnetic state for $x < 0.08$. When $x$ approaches the critical composition ($x \sim$ 0.08), the Fermi liquid temperature is suppressed to zero Kelvin, and non-Fermi liquid behavior is observed. These results demonstrate the strong interplay between charge and spin degrees of freedom in the double layered ruthenates.

cond-mat.str-el↗

arXiv2008

Unusual heavy-mass nearly ferromagnetic state with a surprisingly large Wilson ratio in the double layered ruthenates (Sr$_{1-x}$Ca$_{x}$)$_{3}$Ru$_{2}$O$_{7}$

We report an unusual nearly ferromagnetic, heavy-mass state with a surprisingly large Wilson ratio $R_{\textrm{w}}$ (e.g., $R_{\textrm{w}}\sim$ 700 for $x =$ 0.2) in double layered ruthenates (Sr$_{1-x}$Ca$_{x}$)$_{3}$Ru$_{2}$O$_{7}$ with 0.08 $< x <$ 0.4. This state does not evolve into a long-range ferromagnetically ordered state despite considerably strong ferromagnetic correlations, but freezes into a cluster-spin-glass at low temperatures. In addition, evidence of non-Fermi liquid behavior is observed as the spin freezing temperature of the cluster-spin-glass approaches zero near $x \approx$ 0.1. We discuss the origin of this unique magnetic state from the Fermi surface information probed by Hall effect measurements.

cond-mat.str-el↗