Table of Contents
International Journal of Superconductivity
Volume 2014, Article ID 957045, 15 pages
http://dx.doi.org/10.1155/2014/957045
Research Article

Charge and Spin Currents in Ferromagnet-Insulator-Superconductor Tunneling Junctions Using Hg-1223 High- Superconductor

Department of Electrical and Electronic System Engineering, Utsunomiya University, 7-1-2 Yoto,Utsunomiya, Tochigi 321-8585, Japan

Received 25 April 2014; Revised 7 July 2014; Accepted 8 July 2014; Published 26 August 2014

Academic Editor: Zigang Deng

Copyright © 2014 Michihide Kitamura et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Charge and spin currents along the -axis in ferromagnet-insulator-superconductor (F/I/S) tunneling junctions have been studied within the framework of the tunneling Hamiltonian model. As a superconductor , HgBa2Ca2Cu3O8+δ (Hg-1223) with copper-oxide high- superconductor has been selected, and as a ferromagnet F, Fe metal with bcc structure has been selected for simplicity. The electronic structures of above materials have been calculated on the basis of the band theory using the spin-polarized self-consistent-field data for the atomic orbital energies and the universal tight-binding parameters (UTBP) for the interactions. For the and defined in the present paper, which are tunneling probabilities of the majority and the minority spin electrons, it is shown that the condition means the standard F/I/S tunneling junction with a nonmagnetic insulating layer, and the condition means the F/I/S tunneling junction with a magnetic insulating layer showing a detectable magnetization. We have found that the charge current and the differential conductance nearly remain the same as the change of , but the spin current is largely changed due to the change of . As an experimental method to detect the change of the spin current, the validity of an X-ray magnetic circular dichroism (XMCD) has been pointed out.