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The thickness-driven spin-reorientation transition of Co/Au(1 1 1) is studied via in situ Kerr microscopy. On varying the premagnetization conditions in external field of in-plane or normal orientation, the magnetic switching into a final remanent state from an in-plane field is investigated. The quantitative analysis of the Kerr rotation derived from Kerr microscopy images allows the determination of the population of different magnetic phases as a function of thickness. Coexisting magnetic phases with preferred in-plane and out-of-plane magnetization orientation are identified. The overall switching behaviour is explained by thermal activation of magnetic domains. We show that there is a population of orthogonal bistable magnetic domains, which can be remanently switched between out-of-plane and in-plane orientation by the appropriate magnetic field. This quantity is related to the intersection of the population of states for in-plane and out-of-plane magnetization.

A new and simple method for the preparation of magnetic dot arrays is introduced. Diblock copolymer micelles with a silica core are used as template for the generation of nanostructure arrays. The silica cores are utilized as mask for ion milling preparation. The morphology and size of the silica and magnetic dot arrays are discussed. The magnetic dots are made from Co/Pt multilayer films. Ferromagnetic dots with a diameter well below 20 nm and perpendicular easy axis of magnetization are created. The switching behavior changes from domain wall motion, dominant in the film, to single domain particle switching in the dots. The magneto-optic saturation signals and the evolution of magnetic anisotropy are discussed.

We present a simple method for the production of magnetic antidot arrays utilizing polystyrene-poly-2-vinylpyridine micelles filled with amorphous SiO 2 . By dip coating, a micellar monolayer is deposited onto Co/Pt multilayers. A hexagonal pattern with periodicity of 80 nm is obtained. By Ar + ion etching the micelle layer is transformed into an antidot array due to preferred sputtering of the SiO 2 core. Further ion bombardment transfers the pattern into the magnetic film and leads to a reorientation of the perpendicular to in-plane easy axis which is attributed to intermixing of the Co/Pt multilayers.

We report the fabrication of magnetic films using electron cyclotron resonance ion beam sputtering. The films consist of a Pt buffer layer, a thin magnetic Co layer and a Pt cap. Varying the thickness of the layers, we can tune the magnetic properties and a uniaxial perpendicular magnetic anisotropy can be obtained. Materials like amorphous silicon oxide, amorphous carbon, glass, mica and potassium bromide have been used as substrates. We have analyzed the structure of Co/Pt films on amorphous carbon by means of transmission electron microscopy. The analysis reveals that the buffer layers are polycrystalline with a (1 1 1)-texture, which increases with Pt thickness. The average grain-size is linearly correlated with the total thickness of the Pt buffer layer. While Co grows predominantly in its HCP stacking with c -axis aligned parallel to the surface normal, FCC grains with a strong (1 1 1) texture are also found. Scanning tunneling microscopy investigations reveal an average surface roughness of the Pt buffer layer of 3.0 A . For buffer thickness ⩾ 60 A we find similar magnetic properties for all Co films, not depending on the substrate materials. Co films of 4–8 A thickness exhibit a perpendicular easy axis of magnetization, while a spin reorientation transition is found in a thickness range of 8–13 A. Above 13 A an in-plane easy axis of magnetization is obtained.

The magnetic properties of ultrathin Co films grown on Cu (1 1 13) are investigated by means of the magneto-optic Kerr effect. Applying fields within the film-plane, different ellipticities are found parallel and perpendicular to the step edges. This disparity of the magneto-optical signals in the two perpendicular directions results from a canting of the magnetization that causes a mixing of longitudinal and polar Kerr effect. The canting angle of the magnetization with respect to the surface-plane is calculated. The dependence of the magnetization canting on film thickness is studied systematically.

A new procedure is presented which can be easily applied to separate longitudinal and polar Kerr signals. The method is advantageous particularly in systems where in-plane and out-of-plane states of magnetization are involved in the reversal process. The feasibility of the method is demonstrated at the spin-reorientation transition in Co/Au(1 1 1) films.

A new method to fabricate arrays of ferromagnetic nanostructures is presented which is based on copying the morphology of self-assembled organic layers via ion milling into ferromagnetic Co/Pt multilayers. The self-assembly of diblock copolymer micelles is used. A very flexible tuning of the magnetic properties is possible via the variation of the multilayer composition. The impact of the growth method on the magnetic properties of the multilayer is described and the spin reorientation in Co/Pt discussed. It is demonstrated that arrays of ferromagnetic and superparamagnetic particles can be fabricated with particle sizes < 20 nm. The proposed method gives direct access to the tailoring of magnetic properties of nanosized objects.

We study two‐dimensional electron gases subjected to modulated potentials and magnetic fields. With mask techniques it is possible to prepare lateral magnetic superlattices with periods below 100 nm. For a sufficiently strong modulation of the magnetic field at the location of the 2DEG at such small periods, optimized heterostructures with extremely shallow 2DEGs are required. Here, we report on the development of shallow HEMTs containing 2DEGs less than 20 nm below the surface and compatible deposition techniques for the magnetic layers.

Fundamental experiments in magnetism deal with phase transitions. A well-known example is the transition from ferro-to paramagnetism which is commonly observed via the magnetic susceptibility. The susceptibility is defined as the response of magnetization due to the alteration of a magnetic field. Close to the Curie temperature TC the magnetization tends to zero on the average as the ordering effect of the exchange interaction is compensated by the disconcerting action of thermal fluctuations of the spins. Above TC , the ferromagnet becomes paramagnetic. This transition features a very well-pronounced susceptibility peak 1‐ 4 that can be eas

We present a method to separate the longitudinal, polar, and equatorial magnetization components that may contribute to a mixed magneto-optical Kerr-effect signal and demonstrate how the spin-reorientation transition (SRT) can be investigated by means of simple Kerr magnetometry. In a Co/Au(111) film with thickness within the SRT region we find hysteresis loops with nonvanishing remanence in all three components when a field is applied within the film plane. A vertical field, however, drives the same film into a single domain state exhibiting full remanence. The fact that remanence is found in all magnetization components, and full remanence is obtained in a vertical field, rules out that the transition proceeds via a state of canting of magnetization and indicates that it proceeds via a state of coexisting phases.