Studies On The Electrical And Magnetic Properties In NiMn/NiFe/In/Fe Spin Valves

Since the discovery of giant magnetoresistance(GMR) effect in 1998,much interest has been focused on GMR of spin valves due to its applications in various fields and importance in basic research.On one hand,spin-valve has important application value.For example,the magnetic recording density has significantly improved because spin valves has been used in magnetic recording technology.On the other hand,many physics issues in this community need further investigation.For example,as the key structure of spin valves,the mechanism of the exchange bias in ferromagnet(FM)/antiferromagnet(AFM) bilayers is still open.Many physics issues in this community need further investigation.Magnetic and magneto-transport properties of spin valves depend not only on the structure, materials and thickness of constituent layers,but also on the fabrication process.Therefore,it enables the properties of spin valves to improve by perfecting the fabrication process and changing the materials or thickness of constituent layers.Indium is predicted to have a good effect on transport applications because its electrons have long mean free path.This may improve the ganit magnetoresistance effect.Moreover,indium has a good stability and conductivity,and it is an important material for preparing well-performance electronic components.As far as we known there is no previously report about the magnetic features and MR effect of SVs with Indium nomagnetic layer.Therefore,the study of NiMn/NiFe/In/Fe spin-valves has important significance for both the basic theoretical research and applied research1) NiMn/NiFe/In/Fe spin valves were grown by dc magnetic sputtering for NiMn/NiFe layers and ion beam sputtering for In/Fe layers on well cleaned glass or silicon substrates at room temperature.2) The MR of samples was studied,and it is found that the saturation field of MR of un-annealed samples are very small(＜200Oe),but the annealed samples have a large saturation of MR(＞5000Oe).3) The experimental MR data were given a reasonable and good fitting by the Langevin-like relation MR = MR_FM + MR_SPML(x),and were analyzed with the spin-relevant scattering theory and the argument of "interfacial loose spins" used by Slonczewski.The MR effect is composed of the low-field MR and the high-field MR. The low-field MR,which corresponds to ferromagnetic contribution MR_FM,enhanced as the temperature was lowered.The high-field MR mainly corresponds to superparamagnetic effect at the intermixed interface.4) The annealed temperature dependence of MR,coercivity and the saturation field of magnetization were studied and the value of these three parameters has enhanced as the temperature was raised,which is related to the transformation of materials' magnetism and variation of interface's structure.5) The MR is related to the velocity of growth and the value is more large when the velocity is smaller.6) The anisotropy of sample was studied and found the anisotropy is profound.Therefore, the experimental MR must embody anisotropic magnetoresistance and gaint magnetoresistance.