arXiv subjects

Y. S. Gui

Publications and source records attributed to Y. S. Gui.

24 records · Page 2Linked to original sources

arXiv2007

Quantized spin excitations in a ferromagnetic microstrip from microwave photovoltage measurements

Quantized spin excitations in a single ferromagnetic microstrip have been measured using the microwave photovoltage technique. Several kinds of spin wave modes due to different contributions of the dipole-dipole and the exchange interactions are observed. Among them are a series of distinct dipole-exchange spin wave modes, which allow us to determine precisely the subtle spin boundary condition. A comprehensive picture for quantized spin excitations in a ferromagnet with finite size is thereby established. The dispersions of the quantized spin wave modes have two different branches separated by the saturation magnetization.

cond-mat.str-el↗

arXiv2006

Realization of a Room-Temperature Spin Dynamo: The Spin Rectification Effect

We demonstrate a room temperature spin dynamo where the precession of electron spins in ferromagnets driven by microwaves manifests itself in a collective way by generating d.c. currents. The current/power ratio is at least three orders of magnitude larger than that found previously for spin-driven currents in semiconductors. The observed bipolar nature and intriguing symmetry are fully explained by the spin rectification effect via which the nonlinear combination of spin and charge dynamics creates d.c. currents.

cond-mat.mtrl-sci↗

arXiv2005

Resonances in Ferromagnetic Gratings Detected by Microwave Photoconductivity

We investigate the impact of microwave excited spin excitations on the DC charge transport in a ferromagnetic (FM) grating. We observe both resonant and nonresonant microwave photoresistance. Resonant features are identified as the ferromagnetic resonance (FMR) and ferromagnetic antiresonance (FMAR). A macroscopic model based on Maxwell and Landau-Lifschitz equations reveals the macroscopic nature of the FMAR. The experimental approach and results provide new insight in the interplay between photonic, spintronic, and charge effects in FM microstructures.

cond-mat.other↗

arXiv2004

Giant spin-orbit splitting in a HgTe quantum well

We have investigated beating patterns in Shubnikov-de Haas oscillations for HgTe/Hg_{0.3}Cd_{0.7}Te(001) quantum wells with electron densities of 2 to 3 X 10^{12} cm^{-2}. Up to 12 beating nodes have been observed at magnetic fields between 0.9 and 6 T. Zero magnetic field spin-orbit splitting energies up to 30 meV have been directly determined from the node positions as well as from the intersection of self-consistently calculated Landau levels. These values, which exceed the thermal broadening of Landau levels, k_B T, at room temperature, are in good agreement with Rashba spin-orbit splitting energies calculated by means of an 8 X 8 kp Kane model. The experimental Shubnikov-de Haas oscillations are also in good agreement with numerical simulations based on this model.

cond-mat.mes-hall↗

arXiv2003

Current heating of a magnetic 2DEG in HgMnTe/HgCdTe quantum wells

Heating caused by electrons with excess kinetic energy has been investigated in a magnetic two-dimensional electron gas, M2DEG, in HgMnTe/HgCdTe(001) quantum wells. The temperature of the Mn ions, T_Mn, has been determined by the node positions in the beating pattern in Shubnikov-de Haas oscillations.The experimental dependence of T_Mn on current and therefore on electron temperature, is in excellent agreement with a rate equation model. Results with this model show that the energy transfer rate from the electrons to the Mn system is proportional to the Mn concentration.

cond-mat.str-el↗

arXiv2002

Interplay of Rashba, Zeeman and Landau splitting in a magnetic two dimensional electron gas

The transport properties of a magnetic two dimensional electron gas consisting of a modulation doped n type HgMnTe/HgCdTe quantum well, QW, have been investigated. By analyzing the Shubnikov-de Haas oscillations and the node positions of their beating patterns, we have been able to separate the gate voltage dependent Rashba spin-orbit splitting from the temperature dependent giant Zeeman splitting. It has been experimentally demonstrated that the Rashba spin-orbit splitting is larger than or comparable to the $sp-d$ exchange interaction induced giant Zeeman splitting in this magnetic 2DEG even at moderately high magnetic fields.

cond-mat.str-el↗