We show experimentally and by model calculations that in finite, nonellipsoidal, micrometer size magnetic thin film elements the dynamic magnetic eigenexcitations (spin waves) may exhibit strong spatial localization. This localization is due to the formation of a potential well for spin waves in the highly inhomogeneous internal magnetic field within the element.

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The recently discovercd oscillating exchange effcct in iron-chromium rnultilayers can bcst be studied on an epitaxial iron sandwich with a wcdge shaped chromium interlayer. Domain patterns arc analyzed as wcll as magnetization curves on such samplcs using magnctooptical techniques. Unusual domains are found in zones around thc transitions between ferromagnetic and antifcrromagnetic exchange. Also thc rnagnctij.ation curves for largcr chromium thickness show some peculiar fcaturcs. The interprctation of these patterns invokcs coupling bctween the iron layers which favours a right angle betwccn the magnetization directions in both layers. Such a non-collinear interaction can be derived phenomcnologically from a biquadratic coupling as introduccd earlicr in thc analysis of spin structures in oxidcs. A biquadratic coupling can be understood either as a second order Heisenberg or a sccond order Dzyaloshinskii interaction. In the course of these investigations domain observations proved to be a uscful and scnsitivc method to detcct locally the nature of interactions between fcrromagnetic layers.Die kurzlich cntdecktc oszillicrendc Wechselwirkung in Eisen Chrom-Vielfachschichtcn kann am bcsten an einer cpitaxialcn Schichtanordnung mit ciner kcilformigcn Chromzwischenschicht studiert wcrden. Die auf solchen Proben beobachtbarcn Domanenstrukturen sow.ie dic Magnctisierungskurven werden mit magnctooptischen Vcrfahrcn untcrsucht. Im Bercich der b e r g a n g c zwischen fcrromagnetischer und antifcrromagnetischer Kopplung werden Zonen ungewijhnlicher Muster cntdeckt. Auch die Magnetisierungskurven fur groflerc Chrom-Schichtdickcn zeigtcn cigentumlichc Zuge. Die Beobachtungen lassen sich erkliren, wcnn einc zusltzliche Kopplung der Schichtcn angenommen wird, die cincn rcchten Winkel zwischcn den Magnetisierungsrichtunecn in bciden Schichtcn begunstigt. Phiinomenologisch ergibt sich eine solche nicht-kollineare Kopplung aus dcr Annahme eincr biquadratischcn Wechselwirkung, wic sie fruher in dcr Analyse von Spinstrukturen rnagnetischer Oxide eingcfuhrt wurde. Einc biquadratische Kopplung lant sich entwcder als Heisenberg-oder DryaloshinskiiWechselwirkung zweiter Ordnung interpretiercn. Dornanenbeobachtungen erwiesen sich im Laufe dieser Untersuchung als empfindlichc Methodc zur IJntcrsuchung des Charaktcrs der Kopplung in Vielfachschichten.

We report on the observation of quantized surface spin waves in periodic arrays of magnetic Ni 81 Fe 19 wires by means of Brillouin light scattering spectroscopy. At small wavevectors (q || ≅ 0 -0.9·10 5 cm -1 ) several discrete, dispersionless modes with a frequency splitting of up to 0.9 GHz were observed for the wavevector oriented perpendicular to the wires. From the frequencies of the modes and the wavevector interval, where each mode is observed, the modes are identified as dipole-exchange surface spin wave modes of the film with quantized wavevector values determined by the boundary conditions at the lateral edges of the wires. With increasing wavevector the separation of the modes becomes smaller, and the frequencies of the discrete modes converge to the dispersion of the dipole-exchange surface mode of a continuous film.Patterned magnetic films are attracting increasing interest due to their potential applications in magnetic storage devices and sensors. Although static properties and coupling phenomena in magnetic films patterned on the micron scale have been studied extensively [1,2,3,4], high-frequency dynamic properties of such films have been rarely investigated. On the other hand, the study of spin wave properties in conventional finite size systems is well established, such as the investigation of so-called Walker-modes in magnetic spheroids [5], and of dipolar-dominated surface modes (Damon-Eshbach modes) in finite-thickness slabs with infinite lateral dimensions [6]. For periodic, micron-sized magnetic structures such a study has been still lacking, likely due to the high requirements both concerning the sample quality and the performance of the Brillouin light scattering experiment to detect the rather weak spin wave signals. In this Letter we report on the observation of quantization of spin waves in an array of magnetic wires. The quantization effects are identified as being due to the finite width of the wires. The evolution of the Damon-Eshbach mode of a continuous film from the discrete eigenmode spectrum of the wires with increasing wavevector, i.e., with diminishing influence of the finite size effect, is demonstrated and quantitatively described by a model based on quantized dipoleexchange modes. We show that both the frequency values and the wavevector intervals, where these modes are observed, are in a good agreement with our proposed model. The samples are made of a 200 Å thick permalloy (Ni 81 Fe 19 ) film deposited in UHV onto a Si(111) substrate by means of e-beam evaporation. Patterning was performed using X-ray lithography. The patterning masks were fabricated by means of a JEOL 5D2U nanopattern generator at 50 keV. X-ray exposure was performed at the super-ACO facility (LURE, Orsay, France) using a negative resist with a lift-off process with Al coating and ion milling. Two samples with periodic arrays of wires with a wire width w=1.8 µm and distances between the centers of the wires, Λ, of 2.5 µm and 4 µm (i.e., wire separations of 0.7 µm and 2.2 µm) were prepared for the inv...