Study on spin control in N-VI diluted magnetic semiconductor composite structures

我们研究了Ⅳ-Ⅵ族化合物GeTe基稀磁半导体及其多层结构的（1）新型稀磁半导体的制备，（2）利用相变技术制备铁磁精细结构，（3）磁性控制和自旋输运现象，并获得了以下结果（1）通过射频溅射制备了具有类似的3d过渡金属（从Ti到Ni）组成（x ≤ 0.15）的GeTe基DMS。在Ge_ Mn_xTe和Cr、Fe掺杂的薄膜中观察到了铁磁有序<1-x>。（2）用聚焦激光束（光斑尺寸为1.2 μ m^2）在顺磁非晶Ge_ Mn_xTe薄膜上成功地形成了宽度为1.0 μ m的晶线<1-x>。辐照后，通过B测试证实了晶丝的铁磁相 ...更多信息 （3）为了控制Ge_ Mn_xTe的矫顽场，制备<1-x>了Ge_<1-x>Mn_xTe/GeTe/Ge_ Mn<1-x>_xTe/MnTe多层膜。在M-H滞后中观察到中间肩，这表明两个Ge_ Mn_xTe层中存在选择性开关<1-x>。多层膜的磁电阻率为4.9%，比单层膜的磁电阻率（0.37%）提高了一个数量级。成功<1-x>地制备了具有相同Mn组分但载流子浓度在10 <19>~ 10 μ <21>cm ~ 3<-3>范围内不同的Ge_ Mn_xTe薄膜。随着载流子浓度的增加，自发磁化强度增加，矫顽场减小。这表明了通过控制载流子浓度来选择性磁化切换的可能性。用磁输运测量研究了磁相变。临界指数的值接近海森堡模型比平均场模型

We have studied (1) the preparation of new diluted magnetic semiconductors (DMSs), (2) fabrication of ferromagnetic fine structure using phase change technique, and (3) magnetic property control and spin transport phenomena, for IV-VI compound GeTe based DMSs and its multi-structures, and obtained the following results(1) GeTe based DMSs having the similar composition (x〜0.15) of 3d transition metals (from Ti to Ni) have been prepared by a rf sputtering. Ferromagnetic order was newly observed for Cr and Fe doped films in addition to Ge_<1-x>Mn_xTe. The higher Curie temperature 100 K was obtained for Fe doped film with the lower carrier concentration than the other ferromagnetic GeTe based DMSs(2) The crystalline wire with 1.0 μ m width has been successfully formed in a paramagnetic amorphous Ge_<1-x>Mn_xTe film by irradiating a focused laser beam through the objective lens (beam spot size=l.2 μ m^2). After the irradiation, the ferromagnetic phase of crystalline wires was confirmed by b … More oth the M-H curves and magnetotransport measurements(3) In order to control the coercive field of upper Ge_<1-x>Mn_xTe layer, Ge_<1-x>Mn_xTe/GeTe/Ge_<1-x>Mn_xTe/MnTe multilayers were fabricated. The intermediate shoulder was observed in the M-H hysteresis, which suggested the selective switching in the two Ge_<1-x>Mn_xTe layers. The magnetoresistance ratio in multilayer is 4.9 %, which is one order larger than that in single layer (0.37 %). Ge_<1-x>Mn_xTe films having the same Mn composition but different carrier concentrations ranging from 10^<19> to 10^<21> cm^<-3> have been successfully prepared. The spontaneous magnetization increased and the coercive field decreased with increasing carrier concentration. This suggested the possibility of selective magnetization switching by controlling the carrier concentration. The magnetic phase transition has been investigated using magnetotansport measurements. The values of the critical exponents were close to those for the Heisenberg model than for the mean field model Less