Yan Zhou et al 2009 New J. Phys. 11 103028 doi:10.1088/1367-2630/11/10/103028
Zero-field precession and hysteretic threshold currents in a spin torque nano device with tilted polarizer
Yan Zhou1,3, S Bonetti1, C L Zha1 and Johan Åkerman1,2
Show affiliationsUsing nonlinear system theory and numerical simulations, we map out the static and dynamic phase diagrams in the zero applied field of a spin torque nano device with a tilted polarizer (TP). We find that for sufficiently large currents, even very small tilt angles (β>1°) will lead to steady free layer precession in zero field. Within a rather large range of tilt angles, 1°<β<19°, we find coexisting static states and hysteretic switching between these using only current. In a more narrow window (1°<β<5°) one of the static states turns into a limit cycle (precession). The coexistence of current-driven static and dynamic states in the zero magnetic field is unique to the TP device and leads to large hysteresis in the upper and lower threshold currents for its operation. The nano device with TP can facilitate the generation of large amplitude mode of spin torque signals without the need for cumbersome magnetic field sources and thus should be very important for future telecommunication applications based on spin transfer torque effects.
-
GENERAL SCIENTIFIC SUMMARY
Introduction and background. Spin transfer torque can be used to reverse the magnetic state in so-called spin transfer torque random access memory (STT-RAM), or excite coherent spin waves at GHz frequencies in spin torque oscillators (STOs). In conventional STOs with in-plane magnetizations, one needs to apply a large magnetic field for signal generation, which is a significant complication and limits the miniaturization of STO-based devices. Zero field STO operation has consequently become an intensely researched topic.Main results. Using an analytical eigenvalue analysis, and complementing it with magnetodynamic simulations, we map out the detailed static and dynamic phase diagram of a novel spin torque device where the magnetization of the fixed layer is tilted at an arbitrary angle out of the film plane. While this device has the combined advantage of zero-field operation and large signal output, we show that it also possesses a surprisingly rich phase diagram with hysteretic switching between coexisting static and dynamic states at zero applied field.
Wider implications. The tilt angle of the polarizer magnetization introduces a new degree of freedom in spin torque devices and may open up a wide range of polarizer angle dependent phenomena in both oscillatory devices and STT-RAM.
Figure. (a) Schematic of a tilted polarizer spin torque nano device. (b) Two coexisting spiral and node type eigenstates. Brown region: node type eigenstates; blue region: spiral type eigenstates. The yellow and green curves represent two examples of the dynamical evolution of the magnetization which finally relaxes in S and N regions, respectively. - PACS
-
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
- Subjects
- Dates
-
Issue 10 (October 2009)
Received 2 July 2009
Published 21 October 2009
-
Zero-field precession and hysteretic threshold currents in a spin torque nano device with tilted polarizer
Yan Zhou et al 2009 New J. Phys. 11 103028
-
Controlled synthesis of high-quality nickel sulfide chain-like tubes and echinus-like nanostructures by a solution chemical route
Ya-Hui Zhang et al 2007 Nanotechnology 18 485609
-
Focusing a helium atom beam using a quantum-reflection mirror
H Christian Schewe et al 2009 New J. Phys. 11 113030
-
Computational modelling of a non-viscous fluid flow in a multi-walled carbon nanotube modelled as a Timoshenko beam
N Khosravian and H Rafii-Tabar 2008 Nanotechnology 19 275703
-
Einstein-aether as a quantum effective field theory
Benjamin Withers 2009 Class. Quantum Grav. 26 225009
-
Pressure-induced magnetic transition in Fe3O4 and CoFe2O4 spinels
G Subías et al 2009 J. Phys.: Conf. Ser. 190 012089
-
Oscillations and instabilities of fast rotating neutron stars
Erich Gaertig and Kostas D Kokkotas 2009 J. Phys.: Conf. Ser. 189 012016
-
Variable dampers for earthquake protection of benchmark highway bridges
S N Madhekar and R S Jangid 2009 Smart Mater. Struct. 18 115011
-
Axonal guidance on patterned free-standing nanowire surfaces
Christelle Prinz et al 2008 Nanotechnology 19 345101
-
Stress-corrosion mechanisms in silicate glasses
Matteo Ciccotti 2009 J. Phys. D: Appl. Phys. 42 214006
Users also read
What's this?- Cancer tumors as Metazoa 1.0: tapping genes of ancient ancestors
- AFM stiffness nanotomography of normal, metaplastic and dysplastic human esophageal cells
- The role of the cytoskeleton in cellular force generation in 2D and 3D environments