New magneto-optical transition in ultrathin Fe(100) films

Magneto-optical polar Keer effects in ultrathin bcc Fe(100) films sandwiched by Au layers were investigated in the 1.6–5.3 eV photon energy range at room temperature. A new peak appeared in the off-diagonal conductivity spectrum at around 3.5–4.5 eV for the Fe films thinner than 10 Å. The peak energy is lower for thinner Fe films. The absolute value of ${\mathrm{\epsilon }}_{\mathit{x}\mathit{y}}$ at 3.7 eV in the 3 Å thick Fe film is 2 times as large as that in the bulk Fe.