CONTROL OF SPIN CONFIGURATION OF MAGNETIC ULTRA-THIN FILMS

巨磁电阻（GMR）效应已经在多种材料中被发现。然而，关于非晶材料，迄今为止报道很少。由于非晶磁性薄膜通常具有优良的软磁性能，如低磁导率、高磁导率和相对高的电阻率，因此它们经常被应用于电感读出磁头。对于GMR，我们发现，使用非晶CoFeB的自旋阀表现出相对较大的MR比为4%至6%。这些值与结晶NiFe自旋阀的值相当或甚至更大。B含量为0至10大气压%的NiO/CoFe B/Cu/CoFe B自旋阀研究了自由磁层厚度对巨磁电阻效应的影响。在自旋阀中，观察到巨磁电阻效应，即使当自由磁性层非常薄，下降到1或0.5毫米。对于较低的B含量，MR比迅速增加的自由磁性层的厚度的增加，而对于较高的B含量，MR比表现出最大的厚度大致等于在磁性层中的电子的平均自由程。利用Camley-Barnas模型，如果考虑磁性层与非磁性层界面处电子的镜面反射，则MR比和电阻率的值可以得到一致的解释。

Giant magnetoresistance (GMR) effect has been found in a wide variety of materials. Concerning amorphous materials, however, very little has been reported so far. Since amorphous magnetic films have usually excellent soft magnetic properties, such as low coercivity, high permeability and relatively high resistivity, they have been often applied for inductive readout heads. For the GMR, we found that spin valves using amorphous CoFeB exhibit relatively large MR ratios of 4 to 6%. These values are comparable to or even larger than those of crystalline NiFe spin valves. NiO/CoFeB/Cu/CoFeB spin valves with B content of 0 to 10 atm.% were prepared to investigate the dependence of the giant magnetoresistance effect on the thickness of free magnetic layers. In the spin valves, giant magnetoresistance effects were observed even when the free magnetic layers were very thin down to 1 or 0.5 mm. For lower B content, the MR ratio rapidly increased with the increase of the thickness of free magnetic layers, while for higher B content, the MR ratio exhibited the maximum at the thickness which is roughly equal to the mean free path of electrons in the magnetic layers. By using Camley - Barnas model, the value of the MR ratio and the resistivity can be consistently explained if the specular reflection of electrons is considered at the interface between magnetic and nonmagnetic layers.