Jon Gorchon
University of California, Berkeley
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Featured researches published by Jon Gorchon.
Physical Review B | 2016
Jon Gorchon; Yang Yang; Jeffrey Bokor
Author(s): Gorchon, J; Yang, Y; Bokor, J | Abstract:
Physical Review B | 2016
Jon Gorchon; Richard B. Wilson; Yang Yang; Akshay Pattabi; J. Y. Chen; Li He; Jian Ping Wang; Mo Li; Jeffrey Bokor
Author(s): Gorchon, J; Wilson, RB; Yang, Y; Pattabi, A; Chen, JY; He, L; Wang, JP; Li, M; Bokor, J | Abstract: ©2016 American Physical Society. Ultrafast optical heating of the electrons in ferrimagnetic metals can result in all-optical switching (AOS) of the magnetization. Here we report quantitative measurements of the temperature rise of GdFeCo thin films during helicity-independent AOS. Critical switching fluences are obtained as a function of the initial temperature of the sample and for laser pulse durations from 55 fs to 15 ps. We conclude that nonequilibrium phenomena are necessary for helicity-independent AOS, although the peak electron temperature does not play a critical role. Pump-probe time-resolved experiments show that the switching time increases as the pulse duration increases, with 10 ps pulses resulting in switching times of ∼13 ps. These results raise new questions about the fundamental mechanism of helicity-independent AOS.
Physical Review B | 2017
Richard B. Wilson; Jon Gorchon; Yang Yang; Charles-Henri Lambert; Sayeef Salahuddin; Jeffrey Bokor
Author(s): Wilson, RB; Gorchon, J; Yang, Y; Lambert, CH; Salahuddin, S; Bokor, J | Abstract:
Science Advances | 2017
Yang Yang; Richard B. Wilson; Jon Gorchon; Charles-Henri Lambert; Sayeef Salahuddin; Jeffrey Bokor
Magnetic switching is induced in 10 ps by electrical current pulses. The field of spintronics involves the study of both spin and charge transport in solid-state devices. Ultrafast magnetism involves the use of femtosecond laser pulses to manipulate magnetic order on subpicosecond time scales. We unite these phenomena by using picosecond charge current pulses to rapidly excite conduction electrons in magnetic metals. We observe deterministic, repeatable ultrafast reversal of the magnetization of a GdFeCo thin film with a single sub–10-ps electrical pulse. The magnetization reverses in ~10 ps, which is more than one order of magnitude faster than any other electrically controlled magnetic switching, and demonstrates a fundamentally new electrical switching mechanism that does not require spin-polarized currents or spin-transfer/orbit torques. The energy density required for switching is low, projecting to only 4 fJ needed to switch a (20 nm)3 cell. This discovery introduces a new field of research into ultrafast charge current–driven spintronic phenomena and devices.
Applied Physics Letters | 2015
Akshay Pattabi; Zheng Gu; Jon Gorchon; Yang Yang; J. Finley; OukJae Lee; H. A. Raziq; Sayeef Salahuddin; Jeffrey Bokor
Strong spin-orbit coupling in non-magnetic heavy metals has been shown to lead to large spin currents flowing transverse to a charge current in such a metal wire. This in turn leads to the buildup of a net spin accumulation at the lateral surfaces of the wire. Spin-orbit torque effects enable the use of the accumulated spins to exert useful magnetic torques on adjacent magnetic layers in spintronic devices. We report the direct detection of spin accumulation at the free surface of nonmagnetic metal films using magnetization-induced optical surface second harmonic generation. The technique is applied to probe the current induced surface spin accumulation in various heavy metals such as Pt, β-Ta, and Au with high sensitivity. The sensitivity of the technique enables us to measure the time dynamics on a sub-ns time scale of the spin accumulation arising from a short current pulse. The ability of optical surface second harmonic generation to probe interfaces suggests that this technique will also be useful for studying the dynamics of spin accumulation and transport across interfaces between non-magnetic and ferromagnetic materials, where spin-orbit torque effects are of considerable interest.
Nano Letters | 2018
Roberto Lo Conte; Zhuyun Xiao; Cai Chen; Camelia V. Stan; Jon Gorchon; Amal El-Ghazaly; Mark E. Nowakowski; Hyunmin Sohn; Akshay Pattabi; Andreas Scholl; Nobumichi Tamura; Abdon Sepulveda; Gregory P. Carman; Rob N. Candler; Jeffrey Bokor
Composite multiferroic systems, consisting of a piezoelectric substrate coupled with a ferromagnetic thin film, are of great interest from a technological point of view because they offer a path toward the development of ultralow power magnetoelectric devices. The key aspect of those systems is the possibility to control magnetization via an electric field, relying on the magneto-elastic coupling at the interface between the piezoelectric and the ferromagnetic components. Accordingly, a direct measurement of both the electrically induced magnetic behavior and of the piezo-strain driving such behavior is crucial for better understanding and further developing these materials systems. In this work, we measure and characterize the micron-scale strain and magnetic response, as a function of an applied electric field, in a composite multiferroic system composed of 1 and 2 μm squares of Ni fabricated on a prepoled [Pb(Mg1/3Nb2/3)O3]0.69-[PbTiO3]0.31 (PMN-PT) single crystal substrate by X-ray microdiffraction and X-ray photoemission electron microscopy, respectively. These two complementary measurements of the same area on the sample indicate the presence of a nonuniform strain which strongly influences the reorientation of the magnetic state within identical Ni microstructures along the surface of the sample. Micromagnetic simulations confirm these experimental observations. This study emphasizes the critical importance of surface and interface engineering on the micron-scale in composite multiferroic structures and introduces a robust method to characterize future devices on these length scales.
Physical Review B | 2017
Richard B. Wilson; Yang Yang; Jon Gorchon; Charles-Henri Lambert; Sayeef Salahuddin; Jeffrey Bokor
Author(s): Wilson, RB; Yang, Y; Gorchon, J; Lambert, CH; Salahuddin, S; Bokor, J | Abstract:
2017 Fifth Berkeley Symposium on Energy Efficient Electronic Systems & Steep Transistors Workshop (E3S) | 2017
Amai El-Ghazaly; Daisy O'Mahoney; Charles-Henri Lambert; Jon Gorchon; P. Nigel Brown; Akshay Pattabi; H.-S. Philip Wong; Jeffrey Bokor
Up until now, magnetic nanodots used for magnetic random access memory have required spin-polarized currents to transfer the angular momentum needed to switch the magnetization and thereby switch the magnetic memory bit. This particular switching process, however, is limited to nanosecond or greater timescales — too slow for use as low-level cache in energy efficient electronics systems. On the other hand, this work aims to achieve ultrafast femtosecond switching of nanomagnetic dots without the use of spin-polarized currents. Using just linearly polarized light, several research groups have demonstrated all-optical magnetization switching in large GdFeCo magnetic dots, ranging from several microns [1-4] down to 400 nm [5]; this work characterizes the switching behavior as these dots are scaled down further in size, with the aim of minimizing the energy required for switching the magnetic memory bit. The fabrication process, magnetization behavior and optical switching behavior are additionally characterized to better understand how size affects the functionality of these optically-switchable ferrimagnets. Knowledge of this behavior will allow future developments of simultaneously ultrasmall and ultrafast magnetic memory systems, thereby enabling increased data storage in future electronics.
Physical Review B | 2015
Jon Gorchon; Javier Curiale; A. Cebers; A. Lemaître; Nicolas Vernier; Mathis Plapp; Vincent Jeudy
The shape instability of magnetic domain walls under current is investigated in a ferromagnetic (Ga, Mn)(As, P) film with perpendicular anisotropy. Domain wall motion is driven by the spin transfer torque mechanism. A current density gradient is found either to stabilize domains with walls perpendicular to current lines or to produce fingerlike patterns, depending on the domain wall motion direction. The instability mechanism is shown to result from the nonadiabatic contribution of the spin transfer torque mechanism.
Comptes Rendus Physique | 2013
J. Ferré; Peter J. Metaxas; A. Mougin; J.-P. Jamet; Jon Gorchon; Vincent Jeudy