This book provides an up-to-date review of nanometer-scale magnetism and focuses on the investigation of the basic properties of magnetic nanostructures. It describes a wide range of physical aspects together with theoretical and experimental methods. A broad overview of the latest developments in this emerging and fascinating field of nanostructured materials is given with emphasis on the practical understanding and operation of submicron devices based on nanostructured magnetic materials.
Intensive investigations on nanoscale magnetism have promoted remarkable progressintechnologicalapplicationsofmagnetisminvariousareas.Thete- nical progress of recent years in the preparations of multilayer thin ?lms and nanowires led to the discovery of Giant Magnetoresistance (GMR), imp- ing an extraordinary change in the resistivity of the material by varying the applied external magnetic ?eld. The Nobel Prize for Physics in 2007 was awardedtoAlbertFertandPeterGrun ] bergfortheirdiscoveryofGMR.App- cations of this phenomenon have revolutionizedtechniques for retrieving data fromharddisks.Thediscoveryalsoplaysamajorroleinvariousmagnetics- sors as well as the development of a new generation of electronics. The use of GMRcanberegardedasoneofthe?rstmajorapplicationsofnanotechnology. The GMR materials have already found applications as sensors of low magnetic ?eld, a key component of computer hard disk heads, magnetores- tive RAM chips etc. The "read" heads for magnetic hard disk drives have allowed us to increase the storage density on a disk drive from 1 to 20 Gbit per square inch, merely by the incorporation of the new GMR materials. On the other hand, recently discovered giant magneto-impedance (GMI) mate- als look very promising in the development of a new generation of microwave band electronic devices (such as switches, attenuators, and antennas) which could be managed electrically.
The rate of development in modern digital computer systems and software has led to an almost insatiable demand for ever increasing storage capacities. In response to this demand the memory manufactures and, in particular the disk drive manufacturers have over the last decade or so come forward with spectacular increases in storage capacities and densities. The ? eld of magneticmemoryhasbeenonthefrontierofadvancedmaterialsdevelopment for many years. The momentum now gained in the technology is such that storage densities are increasing at something like one hundred percent per annum and this rate may still be rising. Over the past decades dramatic progress has been made in magnetic storage systems. In the past few years 2 areal densities, currently above 50 Gbits/in , have doubled every 10 months 2 and are expected to reach 100 Gbits/in in the near future. The price per megabytehasdecreasedbyafactorof10inthelastdecadeandispredictedto drop to USD 0. 05 ber megabyte within the next 10 years. The reason is that the intensive investigations in the ? eld of the nanoscale magnetic materials promote to the great progress in various kinds of the magnetic storage media (computer ? oppy disks, sound/video tapes, etc. ). Among the magnetic storage devices, the hard disk drive (HDD) is the dominant secondary mass storage device for computers, and very likely also for homeelectronicproducts in thenear future. The HDDis an integration of many key technologies, including head, medium, head-disk interface, servo, channelcoding/decoding, andelectromechanicalandelectromagneticdevices.
