论文部分内容阅读
由于氧化物巨磁阻薄膜具有十分巨大的巨磁阻效应,因而越来越受到了人们的重视.然而其巨磁阻产生的机理却至今仍不甚清楚,有关这方面的研究显得迫切需要.在多层膜或颗粒膜中其巨磁阻产生的本质通常被理解为一种自旋相关的表面散射的结果.若磁阻比定义为MR=Δρ/ρO=(ρO-ρH)/ρO,其中ρO为零场下的电阻率,ρH为磁场H时的电阻率,则在铁磁转变温度以下MR与磁化强度M之间应该有如下的关系:MR(T,H)=[ρ(O,T)-ρ(H,T)]/ρ(O,T)=A(T)F[│M/M_S│~2],(1)其中M_S为饱和磁化强度,F是│M/M_S│~2的单调函数其值介于0与1之间,当M→0时,F[│M/M_S│~2]=0,而当M→M_S时,F[│M/M_S│~2]=1,(1)式中的A(T)只是一个与温度有关的函数.由该式可以得到如下两个结论:首先,MR的温度关系应该是由(1)式中的A(T)的温度关系来决定,与磁场无关,也即MR(H1,T):MR(H2,T)应该为一常数;其次,对于某一特定的温度,MR(T,H)=CF[│M/M_S│~2],其中C为常数,由此决定了MR的磁场依赖关系.本文将对La_(0.67)Ca_(0.33)MnO_z巨磁阻薄膜中的MR的温度关系和磁场关系作一较详细的实验研究.1 实验
Due to the huge giant magnetoresistance (GMR) effect of giant magnetoresistive film, it attracts more and more attention. However, the mechanism of giant magnetoresistance is still unclear, and research in this area is urgently needed. The nature of the giant magnetoresistance in a multilayer film or a particle film is generally understood as a result of spin-dependent surface scattering. If the MR ratio is defined as MR = Δρ / ρ0 = (ρ0-ρH) / ρ0, Where ρ0 is the electrical resistivity at zero field and ρH is the electrical resistivity at magnetic field H, there should be the following relationship between MR and magnetization M below the ferromagnetic transition temperature: MR (T, H) = [ρ (O , T) -ρ (H, T)] / ρ (O, T) = A (T) F [│M / M_S│ ~ 2], where M_S is the saturation magnetization and F is │M / M_S The monotonous function of │ ~ 2 has a value between 0 and 1. When M → 0, F [│M / M_S│ ~ 2] = 0, and when M → M_S, F [│M / M_S│ ~ 2] = 1, (1) where A (T) is only a temperature-dependent function. From this equation, we can get the following two conclusions: Firstly, the temperature relationship of MR should be represented by A MR (H1, T): MR (H2, T) should be a constant; second, for a specific temperature, MR (T, H) = CF [ M / M_S ~ ~ 2], where C is a constant, which determines the magnetic field dependency of MR. In this paper, the relationship between temperature and magnetic field of MR in La_ (0.67) Ca_ (0.33) A more detailed experimental study.1 experiments