The superconducting spin valve and triplet superconductivity

本项目是关于超导自旋阀系统铁磁/铁磁/超导体(F/F/S)中超导三重态成分的实验研究。本工作的主要目的是探索F/F/S异质结中超导电性和铁磁性相互作用所产生的新效应。这项工作的新颖性在于：(I)关于新发现的S/F结构中三重态超导元件的基本知识的价值，以及(Ii)它们作为逻辑元件、阀门等在自旋电子学中的可能应用。我建议在这个现代物理领域应用的经典方法可以作为实验数据的可靠来源：用于制备F/F/S异质结的超高真空(UHV)沉积方法，用于磁学和输运表征的SQUID和低温电阻测量。为了达到项目的目标，将采取以下步骤：(A)采用超高真空方法制备高质量的F/F/S结构。具体地说，这些系统将具有下面一组层IrMn/F1/Cu/F2/Pb(其中F1和F2=Fe、Ni0.8Fe0.2或Co2Cr1-xFexAl)。请注意，Co2Cr1-xFexAl是Heusler合金。将这种材料与一种常规的超导S层(即铅)进行耦合，本身就是一项具有挑战性的实验任务。对于这种方案，在需要的情况下，将用非磁性金属如铜来稳定F2/Pb界面，以防止F2和Pb材料之间的相互混合。(B)将研究磁性和超导性质之间的相互作用。我们的初步工作认为，作为这一具有挑战性的项目的基础研究成果，(1)将记录F/F/S方案中三重态超导分量的证据，并对其性质进行研究和分析；(2)由于超导三重态自旋阀效应，可以实现超导电性的全开/关开关。

This project is oriented on the experimental investigation of the superconducting triplet components arising in superconducting spin valve system ferromagnet/ferromagnet/ superconductor (F/F/S). The main goal of this work is to explore new effects caused by the interplay between superconductivity and ferromagnetism in F/F/S heterostructures. The novelty of this work is dictated by (i) the value of the fundamental knowledge regarding newly discovered triplet superconducting components in fabricated S/F structures and (ii) their possible application in spintronics as logical elements, valves etc. The classical methods which I propose to apply in this modern physics area can serve as a reliable source of experimental data: Ultra high vacuum (UHV) deposition method for F/F/S heterostructures preparation, SQUID and low temperature resistance measurements for magnetic and transport characterization. In order to reach the objectives of the project the following steps will be taken: (a) The high quality F/F/S structures will be prepared using UHV method. In particular these systems will have the following set of layers IrMn/F1/Cu/F2/Pb (where F1 and F2 = Fe, Ni0.8Fe0.2 or Co2Cr1-xFexAl). Note that Co2Cr1-xFexAl is a Heusler alloy. It is a challenging experimental task itself to couple this material with a conventional superconducting S layer namely Pb. For this scheme in case of need the interface F2/Pb will be stabilized by nonmagnetic metal such as Cu in order to prevent mutual mixing between F2 and Pb materials. (b) The interplay between magnetic and superconducting properties will be investigated. Our preliminary work gives ground to suppose that as a fundamental research result of this challenging project:(1) the evidence of the triplet superconducting components in F/F/S scheme will be registered and their properties will be investigated and analyzed; (2) the full on/off switching of the superconductivity due to the superconducting triplet spin valve effect can be experimentally achieved.