Wenhong Wang

Anomalous temperature-dependent exchange bias in Fe films deposited on Si substrates with the native oxide layer

The temperature dependence of the exchange bias has been investigated in Fe films deposited on the Si substrates with the native oxidize layer. A crossover from negative to positive exchange bias has been observed with increasing temperature at 30 K, accompanied with the maximum of the coercivity. This effect could be understood as a result of the exchange coupling between the ferromagnetic Fe film and the spin-glasslike Fe oxides particles formed spontaneously at the interface, where the direction of their end spins controls the sign of exchange bias.

Characterization of mn-doped 3C-SiC prepared by ion implantation

The characterization of Mn-doped 3C-SiC prepared by ion implantation is reported. Implantation of Mn ions at a dose of 1×1016cm−2 into a 3C-SiC homoepitaxial wafer was carried out. High temperature annealing following the implantation process was found to enhance the ferromagnetic ordering. Transmission magnetic circular dichroism and magnetization investigations demonstrated a ferromagnetic behavior below 245K. The lattice relaxation induced by the postannealing is considered a possible mechanism of this outcome.

Epitaxial Growth and Characterization of Zinc-blende CrAs/GaAs/MnAs/GaAs Multilayers

We report on the growth, structural and transport properties of zinc-blende CrAs/GaAs/MnAs/GaAs multilayers on GaAs(001) substrates. Structural analyses using in-situ reflection high-energy electron diffraction and exsitu cross-sectional transmission electron microscopy confirmed the realization of a zinc-blende crystal structure. Room temperature Hall measurements reveal that the as-grown multilayer exhibits p-type conductivity with a very low resistivity of 0.052 Ω㎝, a high carrier concentration of 6.2×10 19 ㎝ ?3 and a Hall mobility of 1.8 ㎠/Vs. We also observed a clear decrease of the resistivity in samples after low temperature annealing.

Structural And Magnetic Properties Of Mn-Doped SiC

Structural and magnetic properties of manganese (Mn)‐doped silicon carbide (SiC) are investigated. Two Mn‐doping methods of ‘thermal diffusion’ and ‘ion implantation’ are employed using 4H (hexagonal)‐ and 3C (cubic)‐SiC homoepitaxial wafer as the host material. In the case of 4H‐SiC doped using the thermal diffusion method, the extended X‐ray absorption fine structure (EXAFS) analysis suggests that most Mn atoms are incorporated on the interstitial site in the 4H‐SiC lattice, and a paramagnetic behavior is observed in the magnetization measurement. For the Mn‐implanted 3C‐SiC, on the other hand, we detect ferromagnetic behaviors and a Curie temperature is found to reach to 245 K.

Fluorescence EXAFS Analysis of SiC:Mn Films Synthesized on SiC Substrates

The geometric structures for the Mn‐Si films synthesized on a 4H‐SiC homoepitaxial wafers have been investigated by fluorescence EXAFS measurements. The EXAFS analysis revealed that the synthesized Mn‐Si layer formed Mn5Si2 and the Mn atoms in the interlayer between the Mn‐Si and the SiC layer were incorporated on the interstitial site in the 4H‐SiC lattice.

Magnetic and Transport Properties of Mn-Si Films Synthesized on 4H-SiC(0001) Substrates

We report a systematic study of the thickness dependence of magnetic properties in carbon-incorporated Mn-Si films synthesized on a 4H-SiC(0001) homoepitaxial wafer by molecular beam epitaxy (MBE) and an annealing method. Magnetization characteristics reveal a dual-phase characteristic in films with decreasing thickness. The anomalous Hall effect has been observed in the thicker film; however, the observed temperature dependence cannot be explained by traditional anomalous Hall effect theory. The temperature dependent resisitivity indicates the film has a metallic behavior.