Slow Electronic Dynamics in the Paramagnetic State of UTe$_2$

Ferromagnetism or slow paramagnetic relaxation in Fe-doped Li$_3$N?

We report on isothermal magnetization, Mössbauer spectroscopy, and magnetostriction as well as temperature-dependent alternating-current (ac) susceptibility, specific heat, and thermal expansion of single crystalline and polycrstalline Li$_2$(Li$_{1-x}$Fe$_x$)N with $x = 0$ and $x \approx 0.30$. Magnetic hysteresis emerges at temperatures below $T \approx 50\,$K with coercivity fields of up to $μ_0H = 11.6\,$T at $T = 2\,$K and magnetic anisotropy energies of $310\,$K ($27\,$meV). The ac susceptibility is strongly frequency dependent ($f\,=\,10$--$10,000\,$Hz) and reveals an effective energy b…

Transient differential reflectivity of ferromagnetic and paramagnetic phases in the bilayered manganite La1.24Sr1.76Mn2O7

Photoinduced effects in a single crystal of bilayered manganites, La2-2xSr1+2xMn2O7 (x=0.38), were investigated in a wide range of temperatures by pump-probe measurement at a photon energy of 1.6eV. In a ferromagnetic metallic state, significant enhancement of positive rise in differential reflectivity with a slow relaxing time of hundred picoseconds was observed just below Tc=127K, indicating that the reflectivity change with the slow relaxation time constant is induced by laser heating. We have also observed an unconventional fast relaxing component that has a time constant of the order of t…

Slow dynamics of disordered zigzag chain molecules in layered LiVS2 under electron irradiation

Electronic instabilities in transition metal compounds often spontaneously form orbital molecules, which consist of orbital-coupled metal ions at low temperature. Recent local structural studies utilizing the pair distribution function revealed that preformed orbital molecules appear disordered even in the high-temperature paramagnetic phase. However, it is unclear whether preformed orbital molecules are dynamic or static. Here, we provide clear experimental evidence of the slow dynamics of disordered orbital molecules realized in the high-temperature paramagnetic phase of LiVS2, which exhibit…

Anomalous slow dynamics in the metallic helimagnet Gd_{1-x}Y_{x}

Ac-suseptibility measurements were performed in the metallic helimagnet Gd_{1-x}Y_{x} alloy. A remarkable increase of the imaginary part of the ac-suseptibility was observed in the temperature range of the helimagnetic phase. Moreover, a strong nonlinearity of the magnetization was observed at paramagnetic-helimagnetic transition temperature T_{N}. On the other hand, These anomalous behavior were not observed in similar rare-earth helimagnets Ho and Ho_{1-x}Y_{x}. It strongly suggests that the weak magnetic anisotropy of the Gd-moments is responsible for the anomalous slow dynamics in the heli…

Self-consistent renormalization theory of spin fluctuations in paramagnetic spinel LiV2O4

A phenomenological description for the dynamical spin susceptibility $χ({\bf q},ω;T)$ observed in inelastic neutron scattering measurements on powder samples of LiV$_2$O$_4$ is developed in terms of the parametrized self-consistent renormalization (SCR) theory of spin fluctuations. Compatible with previous studies at $T\to 0$, a peculiar distribution in ${\bf q}$-space of strongly enhanced and slow spin fluctuations at $q \sim Q_c \simeq$ 0.6 $Å^{-1}$ in LiV$_2$O$_4$ is involved to derive the mode-mode coupling term entering the basic equation of the SCR theory. The equation is solved self-con…

Dynamics of the lattice and spins in the phase-separated manganite (Eu$_{1-x}$Gd$_{x}$)$_{0.6}$Sr$_{0.4}$MnO$_3$

We investigated slow relaxations of the magnetostriction and residual magnetostriction of the phase-separated system (Eu$_{1-x}$Gd$_{x}$)$_{0.6}$Sr$_{0.4}$MnO$_3$, in which the metamagnetic transition from a paramagnetic insulating state to a ferromagnetic metallic state is accompanied by a lattice shrinkage. The relaxations are well fitted by a stretched exponential function, suggesting the strong frustraction between the double exchange interaction and Jahn-Teller effect. We have revealed that the Gd substitution suppresses the frozen phase-separated phase at low temperatures and stabilizes …

The geometric phase and the dynamics of quantum phase transition induced by a linear quench

We have analysed here the role of the geometric phase in dynamical mechanism of quantum phase transition in the transverse Ising model. We have investigated the system when it is driven at a fixed rate characterized by a quench time $τ_q$ across the critical point from a paramagnetic to ferromagnetic phase. Our argument is based on the fact that the spin fluctuation occurring during the critical slowing down causes random fluctuation in the ground state geometric phase at the critical regime. The correlation function of the random geometric phase determines the excitation probability of the qu…

Slow spin dynamics in the hyper-honeycomb Lattice [(C2H5)3NH]2Cu2(C2O4)3 revealed by 1H NMR studies

We report the results of magnetic susceptibility $χ$ and $^1$H nuclear magnetic resonance (NMR) measurements on a three-dimensional hyper-honeycomb lattice compound [(C$_2$H$_5$)$_3$NH]$_2$Cu$_2$(C$_2$O$_4$)$_3$ (CCCO). The average value of the antiferromagnetic (AFM) exchange coupling between the Cu$^{2+}$ ($S$ = 1/2) spins was determined to be $J$~$\sim$~50 K from the $χ$ measurements. No long-range magnetic ordering has been observed down to $T$ = 50 mK, although NMR lines become slightly broader at low temperatures below 1 K. The broadening of the NMR spectrum observed below 1 K reveals th…

关于理解椭球形4f单体：一个Er³+复合作为电子性质和慢弛豫的数值预测与实验验证

Towards Understanding Prolate 4$f$ Monomers: Numerical Predictions and Experimental Validation of Electronic Properties and Slow Relaxation in a Muffin-shaped Er$^\mathrm{III}$ Complex

该研究通过实验和计算验证了Er³+复合作为电子性质和慢弛豫的特性，揭示了其磁基态和激发态的结构特征。

Spin dynamics in the high-field phases of volborthite

We report single-crystal 51V NMR studies on volborthite Cu3V2O7(OH)2 2H2O, which is regarded as a quasi-two-dimensional frustrated magnet with competing ferromagnetic and antiferromagnetic interactions. In the 1/3 magnetization plateau above 28 T, the nuclear spin-lattice relaxation rate 1/T1 indicates an excitation gap with a large effective g factor in the range of 4.6-5.9, pointing to magnon bound states. Below 26 T where the gap has closed, the NMR spectra indicate small internal fields with a Gaussian-like distribution, whereas 1/T1 shows a power-law-like temperature dependence in the par…