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Mossbauer spectroscopy and the positron annihilation technique have been used to investigate the structure of the amorphous phase of Fe73.5Cu1Nb3Si13.5B9 nanocrystalline alloy annealed at different temperatures. The results show that there is a weak ferromagnetic amorphous boundary with a low hyperfine field. On other hand, the results of positron annihilation indicate that a large amount of vacancy-like defects appears in the amorphous phase at higher temperature. The results of magnetic measurements indicate that the magnetic properties of nanocrystalline alloy are closely related to the density of defects.

The establishment and thermal stability of exchange bias between the ferromagnetic NiFe layer and antiferromagnetic FeMn layer have been studied. We focused on the relationship between FeMn grain size and exchange bias with the size of FeMn grains controlled by varying Cr content in Ni-Fe-Cr alloy buffer layer. The results indicate that, smaller FeMn grains lead to a larger exchange bias field, but the thickness with the exchange bias setting on is larger, which is consistent with Mauri's model. Thermal stability of the exchange bias indicates that, the films with bigger FeMn grains have a higher blocking temperature, which is in agreement with Noshioka's conclusion: bigger antiferromagnetic grains possess higher activation energies and longer relaxation times.

采用一种新的种子层材料:(Ni0.81Fe0.19)1-xCrx,通过改变种子层中Cr原子的含量,使得在其上生长的NiFe/FeMn双层膜的织构和晶粒尺寸产生极大的差异,系统研究了NiFe/FeMn双层膜中FeMn晶粒尺寸和织构对交换偏置的影响.实验结果表明,在FeMn的γ相(111)织构较好的前提下,交换偏置场的大小与织构的差异没有关系;FeMn的晶粒尺寸对交换偏置场有很大影响,较小的反铁磁层晶粒对交换偏置场有利,过大的反铁磁层晶粒不利于交换偏置场.将(Ni0.81Fe0.19)0.5Cr0.5与传统的种子层材料Ta进行了对比,发现前者具有很多优点,是一种可能替代Ta的新型种子层材料.

In Fe-doped Tl-1223 superconducting phase, Fe-dopants significantly destroy superconductivity . Hall coefficient, thermogravimetric measurements and M?ssbauer effect show that Fe-dopants not only directly destroy the integrity of Cu-O layers to low superconduction transition temperature, but also induce extra oxygen to enter lattice. These extra oxygen defects can strengtheningly bind carriers in Cu-O layers, Such binding effect gives rise to decreasing of the carrier density with Fe-doping level increasing. In addition. the extra oxygen results in a deviation of its neibouring Fe(Cu) from center of Cu-O network, and from a new Fe-O coordination. It is important for high-Tc superconducting mechanism to study the structural details and carrier-binding effect of extra oxygen defect on superconducticity.