压力、温度和晶粒尺寸对Fe-N合金的合成及结构的影响

在 1× 1 0 - 3 Pa～ 4 GPa的压力和 5 80～ 930 K温度范围内 ,利用高压技术并结合机械球磨 ,研究了压力、温度和晶粒尺寸对α-Fe与非晶 BN的固态反应的影响 .发现高压和晶粒细化可以极大地促进α-Fe和非晶 BN的固态反应过程 ,α-Fe与非晶 BN发生固态反应的临界晶粒尺寸约 8nm.压力和温度对反应产物及其晶体结构有明显影响 .2 GPa和 80 0 K时 ,反应产物为具有正交结构的 Fe-N新相 ;在 3～ 4 GPa和 690～80 0 K时 ,可形成单一ε-Fex N合金相 ;而在 4 GPa和 930 K以上 ,反应产物由 Fe-N合金相转变为 Fe3B相     

Progress of novel diluted ferromagnetic semiconductors with decoupled spin and charge doping: Counterparts of Fe-based superconductors

Diluted ferromagnetic semiconductors(DMSs) that combine the properties of semiconductors with ferromagnetism have potential application in spin-sensitive electronic(spintronic) devices. The search for DMS materials exploded after the observation of ferromagnetic ordering in Ⅲ-Ⅴ(Ga,Mn)As films. Recently, a series of DMS compounds isostructural to iron-based superconductors have been reported. Among them, the highest Curie temperature T_Co f 230 K has been achieved in(Ba,K)(Zn,Mn)_2As_2. However, most DMSs, including(Ga,Mn)As, are p-type, i.e., the carriers that mediate the ferromagnetism are holes. For practical applications, DMSs with n-type carriers are also advantageous. Very recently,a new DMS Ba(Zn,Co)_2As_2 with n-type carriers has been synthesized. Here we summarize the recent progress on this research stream. We will show that the homogeneous ferromagnetism in these bulk form DMSs has been confirmed by microscopic techniques, i.e., nuclear magnetic resonance(NMR) and muon spin rotation(μSR).