In situ near-field imaging of magnetic domain patterns in ultrathin iron films

Abstract

We report on a scanning near-field optical microscope which operates in ultrahigh vacuum and allows magneto-optical Kerr-effect measurements at variable temperatures and in external magnetic fields with subwavelength lateral resolution. High magneto-optical contrast is achieved by combination with a Sagnac interferometer. In this way, magnetic domain patterns of ultrathin films of Fe/Cu(100), grown at 80 K, were studied in situ. A domain phase consisting of perpendicularly magnetized submicron wide stripes with directional order was observed.

Magnetic stripe domains in ultrathin films and their transformation in magnetic fields

“…As was previously calculated [7,8] and now confirmed by Sagnac-SNOM [4,5], the magnetization reversal of ultrathin films in the vicinity of a spin-reorientation transition passes through a stripe-domain phase. How this phase transforms in a changing magnetic field is shown in Fig.…”

“…This is because most highresolution magnetic microscopy techniques, required for imaging those narrow sub-mm wide stripes, do not (or only in a limited way) allow for the application of external magnetic fields. Only very recently, stripe domains in ultrathin films were imaged in the presence of external magnetic fields by spin-polarized low-energy electron microscopy (SPLEEM) [3] and magneto-optical scanning near-field microscopy (magnetic SNOM) [4,5].In this work, we have studied the magnetic-field induced transformation of the magnetic stripedomain phase for Fe/Cu(1 0 0) ultrathin films by magnetic SNOM. With the SNOM results we can explain the various shapes of magnetization curves (hysteresis loops) measured in the vicinity of the spin-reorientation transition by the polar magneto-optical Kerr effect (polar MOKE).…”

“…The lateral resolution of the instrument is better than 300 nm (at 670 nm wavelength), and the magneto-optical sensitivity amounts to E350 mrad. Details of the experimental setup and the sample preparation are described elsewhere [4,5]. Fig.…”

“…This is because most highresolution magnetic microscopy techniques, required for imaging those narrow sub-mm wide stripes, do not (or only in a limited way) allow for the application of external magnetic fields. Only very recently, stripe domains in ultrathin films were imaged in the presence of external magnetic fields by spin-polarized low-energy electron microscopy (SPLEEM) [3] and magneto-optical scanning near-field microscopy (magnetic SNOM) [4,5].…”

Application of magnetic force microscopy in nanomaterials characterization

“…As with any other optical technique, their resolution is limited by the wavelength of light. This limitation can be circumvented by using near field scanning optical microscopy (NSOM), (Betzig et al, 1991), but very little work has been done in imaging magnetic properties with NSOM (Fumagalli et al, 1998;Meyer et al, 2003;Petersen et al, 1998).…”