Spin waves and the anomalous Hall effect in ferromagnetic (Ga,Mn)As

Chapter 1IntroductionAnother decade is probably straightforward...There is certainly noend to creativity. Gordon Moore, Intel co-founder and chairmanemeritus of the board, speaking of extending the Moore’s Law atthe International Solid-State Circuits Conference, February 2003.Spintronics is an already well-established field of science and technology—the distinction is only in the eye of the beholder, as the whole researcheffort in this field is fuelled by various ideas on how spin phenomena insolids can be rolled out for use in next-gen practical devices. For example,the electron spin with its two possible “up” and “down” orientations canrepresent 0’s and 1’s of binary programming, in analogy to current “on” and“off” states in conventional silicon chips. The basic computational model isthus unchanged. However, the advantages of spin over the charge currentare numerous.Every overclocker 1 knows that the temperature of a standard CPU canreach above 100 ◦ C. The heat is produced by a swarm of electrons beingpushed through integrated circuits, and it takes a lot of extra power to coolthem. Above this temperature, circuit boards, designed by fancy algorithmsto minimise their size and avoid overheating, simply refuse to work. Evenwhen cooling with liquid nitrogen, we get stuck at a mere 7.3GHz clockfrequency [1]. The power bills form a major part of the costs of runningcomputer farms or data centres. 2 Even a single modern gaming rig can eatup to 600–800W when you are playing your Crysis or Fallout. I do not have1 Overclocking is the process of running a computer component at a higher clock rate(more clock cycles per second) than it was designed for or was specified by the manufacturer,usually practised by enthusiasts seeking an increase in the performance of theircomputers. (source: wikipedia.org)2 In 2009 it was estimated that Internet data centres worldwide consume about 2%of global electricity production or ca 30 billion US dollars. Most of this electricity undoubtedlycomes from non-green sources and is mainly needed to keep the servers fromoverheating. To give a rough idea, performing two Google searches we generate aboutthe same amount of CO 2 as boiling a kettle for a cup of tea [2]. In the era when globalwarming is no longer a controversy but rather a fact we are facing, it is worth keeping13