Transverse Magneto-Optical Kerr Effect of FexCux Superlattices for Surface Plasmon Resonance Application:First Principle Study

摘要

Recently, much interest in Surface Plasmon Resonance (SPR) application has been made in optical devices as biosensors in the fields of health diagnosis and food safety. [1, 2] For achieving high sensitivity, one alternative technique has been proposed by optimizing the plasmonic layer that excites the magneto plasmonic effect by employing the transverse magneto-optic Kerr effect (TMOKE), so-called magneto-optical Surface Plasmon Resonance (MOSPR). In the present work, the magnetic and magneto-optical properties of ferromagneticoble metal superlattices, Fex/Cux, where x is the number of atomic-layers, are studied from first-principles calculations. Calculations were carried out by using a full-potential linearized augmented plane wave (FLAPW) method with the generalized gradient approximation. [3] The diagonal and off-diagonal parts of absorptive optical conductivity tensor, Re(σxx) andωIm(σyz), were estimated by linear response theory. As far as the magnetic properties are concerned, a significant increase of magnetic moment of Fe in the system is observed, it ranges between 2.65 and 2.66 µB, while Cu possess an induced magnetic moment, which is characterized by its small value. The optical spectrum Re(σyz) shows the first peak shift of the energy position to 1.7 eV, 2.4 eV and 1.9 eV for x=1, 2 and 3, respectively, compared to value of 2.7 eV for pure body-centered-cubic (bcc) Fe. Assumed the Kretschmann configuration with the 4 × 4 transfer matrix method [4], we have simulated the MOSPR system for blood serum (n=1.346) as a sample. The resonance condition in the SPR spectra occurs at an incident angle of 75.5°. On the other hand, the MOSPR signal in the resonance condition increases proportionally to the number of x in FexCux. The enhancement of the S-shaped resonance of the MOSPR signal is caused by a shift in resonance features observed in reflectance.