BEGIN:VCALENDAR VERSION:2.0 PRODID:-//Talks.cam//talks.cam.ac.uk// X-WR-CALNAME:Talks.cam BEGIN:VEVENT SUMMARY:"\;Novel Spintronics effects based on the Spin-orbit Coupling: Spin-gating and spintronics with antiferromagnets'"\;-Dr. Joerg Wunde rlich\, Hitachi Lab - Dr. Joerg Wunderlich\, Hitachi Lab DTSTART:20121206T143000Z DTEND:20121206T160000Z UID:TALK41219@talks.cam.ac.uk CONTACT:Kimberly Cole DESCRIPTION:The majority of spintronics devices can be associated with one of the two basic physical paradigms of the field. The first paradigm stem s from Mott's two-spin-channel picture of transport in ferromagnets and th e second paradigm is due to Dirac's quantum-realistic spin-orbit coupling. \nThe essential distinction between functionalities of the two types of sp intronics devices is that the "Mott" devices rely on relative magnetizatio n orientations of separate ferromagnetic components and on transport of el ectron's spin between the components. For example\, commercial spintronic devices\, used in modern hard-drive read heads and magnetic random access memories\, are magnetic spin valve structures comprising two ferromagnetic electrodes whose relative magnetization orientations is switched between parallel and antiparallel configurations\, yielding the desired giant or t unnelling magnetoresistance effect [1]. The "Dirac" spintronic devices\, o n the other hand\, rely on a single self-sustaining spin-orbit coupled com ponent with their transport characteristics governed by the subtle effects resulting from the spin-orbit coupling.\nStarting from the anisotropic ma gnetoresistance effect (AMR) present in the ohmic transport regime of bulk ferromagnets\, I will discuss magnetotransport anisotropy in the tunnelli ng and in the Coulomb blockade single electron transport regimes. The Tunn eling Anisotropic Magneto Resistance (TAMR) is an interface effect and ari ses from the dependence of the relativistic tunneling density of state on the orientation of the magnetic moments. [2\, 3] Another class of "Dirac" spintronic devices have the magnetotransport characteristics coded in a si ngle quantity derived directly from the relativistic band structure: the m agnetization-orientation dependent chemical potential. In one particular r ealization of the concept\, the spin-orbit coupled magnet is placed in a s ingle-electron transport channel and the chemical potential controls the h uge Coulomb blockade anisotropic magnetoresistance (CBAMR) of the channel. [4-6] Another realization is a new type of a spin-transistor in which the magnet is completely removed from the transport channel and placed to the capacitively coupled gate.\nAn important property of "Dirac" spintronic d evices based effects is that they are equally present in antiferromagnetic ally ordered systems.\nAntiferromagnets (AFM) have been used in spintronic s devices so far only to pin the magnetization direction of a ferromagneti c electrode through the exchange-bias effect. Recently\, the antiferromagn etic TAMR in a tunnel junction with an AFM electrode of IrMn and a nonmagn etic counter electrode was realized. [7] The magnetization direction of th e AFM IrMn layer was manipulated with a relatively small magnetic field of 50mT by the exchange spring effect of coupled soft NiFe. Moreover\, the A FM TAMR provides a means to study the exchange-bias effect by an electroni c transport measurement.[8]\n\nReferences: \n\n[1] C. Chappert\, A. Fert\, F. N. V. Dau\, Nature Mater. 6\,813-823 (2007). \n[2] C. Gould\, et al.\, Phys. Rev. Lett. 93\, 117203 (2004).\n[3] B.G. Park\, et al.\, Phys. Rev. Lett. 100\, 087204 (2008). \n[4] J. Wunderlich\, et al.\, Phys. Rev. Lett . 97\, 077201 (2006). \n[5] M. Schlapps\, et al.\, Phys. Rev. B 80\, 12533 0 (2009). \n[6] A. Bernand-Mantel\, et al.\, Nature Physics 5\, 920 - 924 (2009). \n[7] B.G. Park\, et al.\, Nature Materials 10\, 5\, 347 (2011). \ n[8] X. Marti\, et al.\, Phys. Rev. Lett 108\, 017201 (2012).\n\n LOCATION:Mott Seminar Room\, Cavendish Laboratory END:VEVENT END:VCALENDAR