Curie温度附近稀磁半导体(Ga,Mn)As的电学噪声谱性质

Electronic noise of diluted magnetic semiconductor (Ga,Mn) As around Curie point

建立了自发噪声谱测量系统来研究稀磁半导体(Ga,Mn)As的电学噪声性质.通过测量(Ga,Mn)As材料的自发噪声谱,发现(Ga,Mn)As的自发涨落会随温度升高而逐渐增大,同时,外加磁场会降低(Ga,Mn)As的自发涨落,这来源于外加磁场导致的(Ga,Mn)As磁畴部分有序化.此外,不同频率的噪声随温度的变化规律有很大差异:当频率低于30kHz的时候,噪声谱和温度的变化关系和热噪声很相似,但数值上明显大于热噪声的值;当频率在30kHz左右的时候,噪声大小和温度成线性关系;当频率大于30kHz以后,在相变点附近噪声大小和温度的关系出现了明显的转折,高频高温噪声的大小和热噪声的理论值非常接近.这些结果有助于深入理解(Ga,Mn)As磁性起源的物理机制.

We have studied the spontaneous fluctuation noise spectrum of（Ga,Mn） As in frequency domian from 1 kHz to 250 kHz. We found that the electronic noise can be reduced by a magnetic field and its magnitude increases with increasing temperature of the（Ga,Mn） As sample. The electrical noise spectra at different frequencies have different temperature dependence and their amplitude changes at the phase transition temperature,suggesting that the phase transition process of（Ga,Mn） As is subtly different from normal magnetic materials. Our results may help understanding the origin of magnetism in（Ga,Mn） As.