Annealing effect on magnetic anisotropy in ultrathin（Ga,Mn）As

We investigated the effect of low temperature annealing on magnetic anisotropy in 7-nm ultrathin Ga0.94Mn0.06As devices by measuring the angle-dependent planar Hall resistance(PHR).Obvious hysteresis loops were observed during the magnetization reversal through the clockwise and counterclockwise rotations under low magnetic fields(below 1000 Gs,1 Gs = 10-4 T),which can be explained by competition between Zeeman energy and magnetic anisotropic energy.It is found that the uniaxial anisotropy is dominant in the whole measured ferromagnetic range for both the as-grown ultrathin Ga0.94Mn0.06As and the annealed one.The cubic anisotropy changes more than the uniaxial anisotropy in the measured temperature ranges after annealing.This gives a useful way to tune the magnetic anisotropy of ultrathin(Ga,Mn)As devices.     

Transport and Capacitance Properties of Charge Density Wave in Few-Layer 2H-TaS2 Devices

We carefully investigate the transport and capacitance properties of few layer charge density wave （CDW） 2HTaS2 devices. The CDW transition temperature and the threshold voltage vary from device to device, which is attributed to the interlayer interaction and inhomogeneous local defects of these micro-devices based on few layer 2H-TaS2 flakes. The nonlinear rather than linear current voltage characteristic of 2H-TaS2 devices is observed in our experiment at low temperature. The temperature dependence of the relative threshold voltage can be scaled to （1 - T /Tr ）^0.5＋δ with δ = 0.08 for the different measured devices with the presence of the CDWs. The conductance-voltage and capacity-voltage measurements are performed simultaneously. At very low ac active voltage, we find that the hysteresis loops of these two measurements exactly match each other. Our results point out that the capacity-voltage measurements can also be used to define the threshold depinning voltage of the CDW, which gives us a new method to investigate the CDWs.