Exchange bias effect and hard disk media studied by means of quantitative magnetic force microscopy

摘要: More than 15 years after its invention, the MFM has become a widespread tool to characterize magnetic materials and structures. However, impact of technique in academic and industrial research declined recent due lack lateral magnetic resolution and possible influence tip stray field on magnetization structure sample. Moreover, profound understanding contrast formation an experiment and hence quantification measured data remains elusive. In first chapter this thesis, image is described by a transfer function theory. The theory combination with experimental methods introduced by van Schendel [9] allows calibration imaging properties and therefore quantitative interpretation measurement (→ 1). All presented thesis were acquired either low temperature ultra high vacuum microscope (LTSFM) or resolution force microscope (hr-MFM) designed and build for investigation hard disk media industrial environment 2). In order improve down about 10 nm, ultrasharp tips high aspect ratio coating thickness only few nanometers have be used. In addition, tip–sample distance during acquisition decreased below nm. In regime, non-magnetic forces, e.g. derWaals force, comparable to force. As consequence, new separate from the non-magnetic contributions (and therefore image) were developed 3.1). Further, geometry the magnetic studied. In sharp, fragile are used, so that any contact destroys tip. achieving not trivial because are typically used micron-sized images, which takes place at distances nanometers. last part chapter, the degradation various geometry, contacts of increasing intensity studied 3.3). The images obtained hr-MFM sparked the interest recording industry technique. knowledge gained the process work wish researchers to perform measurements their led intense interaction between group Basel labs. several visits to these labs importance hr-MFM images became apparent. Up now, performance media, read write heads was mostly characterized spin stand experiments. Although, the MFM resolved micromagnetic written tracks bits great detail, relation to typical quantities determined experiments remained unclear. Hence, new image analysis procedures developed allow extraction head media properties 4). process analysis, it became apparent, todays drives determined by nano-scale physics field. The continuous demand increased storage density throughout decade could only be met astonishingly rapid transfer newly discovered physical phenomena into products computer industry. One example kind use GMR effect [15, 16] read devices such as drives. basis read head so-called spin-valve [87]. components ferromagnetic (FM) layer a magnetization direction stabilized exchange coupling adjacent antiferromagnetic (AF) layer. Although products, detailed qualitative mechanism still lacking. It commonly accepted, interface AF FM plays key role. So far, magnetic structure been XMCD methods. These have the advantage chemical sensitivity, thus principle, state one specific element can accessed. disadvantages limited spacial of XMCD microscopy methods, complexity instrumentation,which involves beam line synchrotron long times. latter makes that require variation external parameters field, tedious. 5, based method discussed determination the uncompensated superior study evolution of domain layers applied field.