Theory of superconducting and magnetic proximity effect in S/F structures with inhomogeneous magnetization textures and spin-active interfaces

Abstract

We present a study of the proximity effect and the inverse proximity effect in a $\text{superconductor}\ensuremath{\mid}\text{ferromagnet}$ bilayer, taking into account several important factors which mostly have been ignored in the literature so far. These include spin-dependent interfacial phase shifts (spin-DIPS) and inhomogeneous textures of the magnetization in the ferromagnetic layer, both of which are expected to be present in real experimental samples. Our approach is numerical, allowing us to access the full proximity effect regime. In Sec. II of this work, we study the superconducting proximity effect and the resulting local density of states in an inhomogeneous ferromagnet with a nontrivial magnetic texture. Our two main results in Sec. II are a study of how Bloch and N\'eel domain walls affect the proximity-induced superconducting correlations and a study of the superconducting proximity effect in a conical ferromagnet. The latter topic should be relevant for the ferromagnet Ho, which was recently used in an experiment to demonstrate the possibility to generate and sustain long-range triplet superconducting correlations. In Sec. III of this work, we investigate the inverse proximity effect with emphasis on the induced magnetization in the superconducting region as a result of the ``leakage'' from the ferromagnetic region. It is shown that the presence of spin-DIPS modifies conclusions obtained previously in the literature with regard to the induced magnetization in the superconducting region. In particular, we find that the spin-DIPS can trigger an antiscreening effect of the magnetization, leading to an induced magnetization in the superconducting region with the same sign as in the proximity ferromagnet.