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San Jose, CA, United States

Marchon B.,San Jose Research Center | Saito Y.,Hitachi Ltd.
IEEE Transactions on Magnetics | Year: 2012

Molecular dynamics modeling of lubricant displacement on a disk during transient heating in a heat assisted recording interface is presented. It is found that in the time and dimension scales expected for high density recording (nanosecond, tens of nanometers), a significant lubricant removal from the heat spot center can occur, leading to the formation of a rim around it. Continuum fluid dynamics calculations were also performed using a temperature dependent Hamaker constant for lubricant-lubricant interactions. These results were in good agreement with the molecular dynamics predictions. © 2012 IEEE.

Pfau B.,TU Berlin | Pfau B.,Helmholtz Center Berlin | Gunther C.M.,TU Berlin | Gunther C.M.,Helmholtz Center Berlin | And 7 more authors.
Optics Express | Year: 2010

We present a method for high-resolution magnetic imaging at linearly polarized partially coherent x-ray sources. The magnetic imaging was realized via Fourier transform holography. In order to achieve elliptical x-ray polarization, three different filters were designed based on the x-ray magnetic circular dichroism effect. We present proof-of-principle images of magnetic nanostructures and discuss the application of the method for future experiments at free-electron laser sources. © 2010 Optical Society of America.

Liu H.,New York University | Bedau D.,New York University | Sun J.Z.,IBM | Mangin S.,CNRS Jean Lamour Institute | And 3 more authors.
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

We present a two-current-pulse temporal correlation experiment to study the intrinsic subnanosecond nonequilibrium magnetic dynamics of a nanomagnet during and following a pulse excitation. This method is applied to a model spin-transfer system, a spin-valve nanopillar with perpendicular magnetic anisotropy. Two pulses separated by a short delay (<500 ps) are shown to lead to the same switching probability as a single pulse with a duration that depends on the delay. This demonstrates a remarkable symmetry between magnetic excitation and relaxation and provides a direct measurement of the magnetic relaxation time. The results are consistent with a simple finite-temperature Fokker-Planck macrospin model of the dynamics, suggesting more coherent magnetization dynamics in this short-time nonequilibrium limit than near equilibrium. © 2012 American Physical Society.

Liu H.,New York University | Bedau D.,New York University | Backes D.,New York University | Katine J.A.,San Jose Research Center | And 2 more authors.
Applied Physics Letters | Year: 2010

Orthogonal spin-transfer magnetic random access memory (OST-MRAM) uses a spin-polarizing layer magnetized perpendicularly to a free layer to achieve large spin-transfer torques and ultrafast energy efficient switching. We have fabricated and studied OST-MRAM devices that incorporate a perpendicularly magnetized spin-polarizing layer and a magnetic tunnel junction, which consists of an in-plane magnetized free layer and synthetic antiferromagnetic reference layer. Reliable switching is observed at room temperature with 0.7 V amplitude pulses of 500 ps duration. The switching is bipolar, occurring for positive and negative polarity pulses, consistent with a precessional reversal mechanism, and requires an energy of less than 450 fJ. © 2010 American Institute of Physics.

Bedau D.,New York University | Liu H.,New York University | Bouzaglou J.-J.,New York University | Bouzaglou J.-J.,CNRS Jean Lamour Institute | And 5 more authors.
Applied Physics Letters | Year: 2010

Spin-transfer switching with short current pulses has been studied in spin-valve nanopillars with perpendicularly magnetized free and reference layers. Magnetization switching with current pulses as short as 300 ps is demonstrated. The pulse amplitude needed to reverse the magnetization is shown to be inversely proportional to the pulse duration, consistent with a macrospin spin-transfer model. However, the pulse amplitude duration switching boundary depends on the applied field much more strongly than predicted by the zero temperature macrospin model. The results also demonstrate that there is an optimal pulse length that minimizes the energy required to reverse the magnetization. © 2010 American Institute of Physics.

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