Single-shot all-optical switching of magnetization in Tb/Co multilayer-based electrodes

Abstract

Ever since the first observation of all-optical switching of magnetization in the ferrimagnetic alloy GdFeCo using femtosecond laser pulses, there has been significant interest in exploiting this process for data-recording applications. in particular, the ultrafast speed of the magnetic reversal can enable the writing speeds associated with magnetic memory devices to be potentially pushed towards tHz frequencies. this work reports the development of perpendicular magnetic tunnel junctions incorporating a stack of tb/co nanolayers whose magnetization can be all-optically controlled via helicity-independent single-shot switching. toggling of the magnetization of the tb/co electrode was achieved using either 60 femtosecond-long or 5 picosecond-long laser pulses, with incident fluences down to 3.5 mJ/cm 2 , for co-rich compositions of the stack either in isolation or coupled to a cofeBelectrode/Mgo-barrier tunnel-junction stack. Successful switching of the cofeB-[tb/co] electrodes was obtained even after annealing at 250 °c. After integration of the [tb/co]-based electrodes within perpendicular magnetic tunnel junctions yielded a maximum tunneling magnetoresistance signal of 41% and RxA value of 150 Ωμm 2 with current-in-plane measurements and ratios between 28% and 38% in nanopatterned pillars. these results represent a breakthrough for the development of perpendicular magnetic tunnel junctions controllable using single laser pulses, and offer a technologically-viable path towards the realization of hybrid spintronic-photonic systems featuring tHz switching speeds. Ferrimagnetic systems based on rare earth (RE)-transition metal (TM) alloys and multilayers have been extensively studied in recent decades, largely due to their potential application in the field of magneto-optical recording 1. The strong perpendicular magnetocrystalline anisotropy inherent to amorphous RE-TM systems have allowed these alloys to play a key role in the historical transition from longitudinal to perpendicular magnetic recording structures 2 , and made them ideal for handling magnetic bit instabilities arising from superparamagnetic effects 3. Binary and ternary RE-TM systems such as GdFeCo, GdCo, TbCo or GdFe are still driving forward new developments pertaining to spintronic devices, including spin valves for magnetic read heads 4 , perpendicular magnetic tunnel junctions (p-MTJs) 5,6 or spin-orbit-torque phenomena 7. Recent works in this field have also revealed that RE-TM-based films (amorphous or multilayered) represent ideal materials for the observation and study of the phenomena of all-optical switching (AOS) 8-10. In these systems, it is possible to switch the magnetization using suitable laser pulses without the application of any external magnetic field. Depending on whether the laser-pulses need to be circularly-polarized, AOS of magnetization can be classed as either helicity-dependent (HD-AOS) or helicity-independent (HI-AOS). Furthermore, subject to the material in question, the switching process can be achieved with either a...

Energy Efficient Control of Ultrafast Spin Current to Induce Single Femtosecond Pulse Switching of a Ferromagnet

“…All optical switching (AOS) of magnetization using ultrashort laser pulses, whether it is helicity dependent [1][2][3][4][5][6] or helicity independent (AO-HIS), [4,[6][7][8][9][10][11][12] exhibits a very interesting out of equilibrium physics as well as promising practical implications. [13] Many attempts to unveil the detailed mechanism of those phenomena have been carried out both theoretically [8,[14][15][16][17][18][19][20][21][22][23][24] and DOI: 10.1002/advs.202001996 experimentally.…”

“…[13] Many attempts to unveil the detailed mechanism of those phenomena have been carried out both theoretically [8,[14][15][16][17][18][19][20][21][22][23][24] and DOI: 10.1002/advs.202001996 experimentally. [1][2][3][4][5][6][7][8][9][10][11][12][25][26][27][28] AO-HIS is observed after a single femtosecond laser pulse and most of the materials showing this effect are gadolinium-based rare earth (RE)/transition metals (TMs) ferrimagnets. [24] AO-HIS has been extensively studied in amorphous GdFeCo alloy.…”

Exchange-driven all-optical magnetic switching in compensated 3d ferrimagnets

“…All-optical switching (AOS) of magnetization using a single ultrashort laser pulse in the absence of a magnetic field [5] was first identified in amorphous ferrimagnetic Gd x (FeCo) 100−x thin films (hereafter referred to as GdFeCo) in 2012 [6]. Great efforts have since been devoted by experimentalists and theoreticians alike to unravel the underlying physical mechanism, with the ultimate aim of designing alternative optically switchable materials with superior functionality [7,8].…”

All-optical spin switching probability in [Tb/Co] multilayers

“…Although, we have used the same damping constant value for Tb and Co atoms to determine the switching probability, as was done in similar works 14 , 25 , the exploration of element-specific damping could provide more information about the switching dynamics of the system as suggested by recent reports 28 . Our simulation and experiments 12 were performed using fs-long pulses to evaluate the optical switching in [Tb/Co]-based systems and only [ / ] and [ / ] showed a clear fluence window for the observation of optical switching using 50 fs pulses (Fig. S2 in the Supplementary data file).…”

“…For instance, systematic experimental studies on the switching ability of RE-based and RE-free multilayered systems performed by El-Hadri et al 8 , demonstrated that engineered synthetic ferrimagnets such as [Ho/Co], [Tb/Co] and [Co/Pt] based multilayers only show HD-AOS. Among all systems switched by HD-AOS, only a few multilayered systems exhibit the possibility of single-shot switching: Pt/Co/Pt/Co/GdFeCo 9 , Pt/Co/Gd 10 , FeCoB/Ta/[Tb/Co] 11 , 12 and Pt/Co/Pt 13 . From a theoretical point of view, only two reports discuss the possibility of TIMS in alloys 14 , 15 .…”