S Mangin

Ultrafast all-optical switching (AOS) in ferromagnets has emerged as a promising route toward dense and energy-efficient magnetic memory. However, its implementation has typically been limited by material-specific polarization requirements or by the need for auxiliary exchange coupling and compositional tuning. Here, we demonstrate that deterministic control of AOS can instead be achieved purely through optical engineering. By tailoring the polarization distribution and focusing of the excitation light, we shift the selectivity from intrinsic material properties to external optical beam shaping. In stand-alone [Pt/Co] _N multilayers, this enables direct control over local heating and optical torques, allowing the system to be driven either into helicity-dependent, multishot domain-wall propagation or into helicity-independent magnetization reversal, without material modification or external bias fields. Our results establish optical beam design as a universal control knob for magnetization dynamics in ferromagnetic systems, defining a scalable pathway for integrating ultrafast spintronic functionality with on-chip photonics.

Rare-earth-free ferrimagnetic oxides are emerging as attractive platforms for investigating ultrafast spin dynamics. Here, we study the photoinduced magnetization dynamics of epitaxial NiCo2O4 (NCO) thin films by the time-resolved magneto-optical Faraday effect using two independent pump–probe configurations: 1030/515 and 800/400 nm. In both measurements, photoexcitation induces an immediate reduction of the magneto-optical signal within the experimental time resolution, followed by a reproducible slower demagnetization component with a characteristic timescale of approximately 5–6 ps and a subsequent recovery on the ∼100 ps timescale. Importantly, this picosecond demagnetization component is observed consistently across the two experimental configurations and excitation wavelengths, demonstrating that it is an intrinsic feature of the ultrafast magnetic response of NCO thin films. Because the earliest-time dip may contain a transient optical contribution, we describe the overall response as type-II-like, rather than assigning a definitive textbook type-II classification solely on the basis of the sub-resolution signal. These results establish a robust two-step ultrafast demagnetization behavior in NCO and highlight rare-earth-free oxide ferrimagnets as promising systems for exploring multisublattice spin dynamics on ultrafast timescales.

We demonstrate single-shot laser-pulse-induced magnetization reversal in rare-earth-free CoFeB/MgO magnetic tunnel junctions (MTJs), a material system widely adopted in spin-transfer torque magnetic random-access memory. By tuning the Ru capping layer thickness, we modify the laser energy absorption profile and observe magnetization reversal from the parallel to antiparallel state, with switching observed for tRu ≥ 2.0 nm. Furthermore, we detect magnetization reversal in a micro-scale MTJ device via the tunnel magnetoresistance effect. Our findings suggest that ultrafast spin transport, dipolar interactions, or a combination of both may contribute to the switching process, although the precise mechanism remains to be clarified. This work represents a significant step toward integrating ultrafast optical control with MTJ technology.

This work investigates the influence of bias voltage on the optical switching behavior of a Tb/Co-based Magnetic Tunnel Junction (MTJ) in an 80-nm diameter pillar device. The experimental results demonstrate enhanced switching performance at high bias voltage, with a maximum switching probability achieved at bias voltage values of 200 and 400 mV. At high bias, Joule heating effect reduces the effective magnetic anisotropy of the pillar device, thereby favoring in-plane magnetization precession, lowering the switching threshold, and expanding the toggle switching window. The optical switching exhibits a pronounced asymmetry, showing a favorable switching under negative voltage polarity. Under this polarity, tunneling electrons are injected toward the top electrode, causing the decrease of magnetic anisotropy in the Tb/Co-based free layer and, therefore, facilitating the magnetization reversal at a laser pulse. The thermal analysis of All-Optical Switching (AOS)-MTJ devices under opposite bias polarities shows a temperature difference of 5–10 K, depending on the pillar diameter. These findings demonstrate voltage-selective control for multiple AOS devices integrated on the same chips, enabling an application for CMOS-compatible magneto-photonic memory.

With growing demand for cooling and rising interest in eco-friendly solutions, researchers are focusing on the development of advanced cooling technologies, including those utilizing the magnetocaloric effect by means of magnetocaloric materials. Such development necessitates a thorough understanding of these types of materials. In this context, a density functional theory (DFT) study of neodymium orthophosphate (NdPO₄) was conducted by employing the GGA + U + SOC approximation. The compound's electronic and magnetic properties, investigated in the monoclinic monazite structure, revealed an antiferromagnetic configuration, which can be described as two antiparallel sublattices, while electronic structure analysis showed a direct band gap energy of 3.39 eV, indicating an insulating behavior. To probe its magnetic properties, sum rules applied to X-ray magnetic circular dichroism (XMCD) and X-ray absorption spectra (XAS) near the M_5,4 edges coupled to pure DFT calculations yielded a total magnetic moment of 1.4 μ_B, where 2.92, -1.64, and 0.105 μ_B are the spin, orbital, and dipolar term contributions, respectively. Additionally, NdPO₄ shows a modest magneto-crystalline anisotropy with the b-axis identified as the hard and the ac plane as the easy magnetization directions. Finally, the superexchange was found to be very weak; however, it remains the driving mechanism over dipole-dipole interaction, especially between nearest neighbors, while driving the transition temperature around 0.32 K.

Multiferroic tunnel junctions (MFTJs), integrating ferroelectric and ferromagnetic functionalities within a single nanoscale device, hold significant promise for nonvolatile, multistate memory and innovative computing paradigms. In conventional MFTJs, tunneling resistance modulation relies primarily on ferroelectric (FE) polarization switching, which alters interfacial electric fields and shifts the Fermi level of adjacent ferromagnetic electrodes. However, achieving high tunnel electroresistance (TER) through this approach demands strong built-in electric fields, which simultaneously hinder FE polarization switching, creating an intrinsic trade-off between reliable data reading and efficient writing. Here, we propose a dual mechanism that combines antiferroelectric (AFE) phase-transition modulation of the evanescent decay states with interfacial spin filtering based on Fe₃GaTe₂/bilayer-α-In₂Se₃/Fe₃GaTe₂ heterostructure. Beyond altering the electrostatic potential as in AFE-FE switching, the transitions between head-to-head type and tail-to-tail type AFE states preserve the centrosymmetric potential profile yet fundamentally modulate the momentum-resolved distribution of evanescent decay rates across the Brillouin zone. When integrated with perfect spin filtering at the Fe₃GaTe₂/α-In₂Se₃ interface, this mechanism yields a giant TER (∼7.6 × 10³%), over 4 times that of conventional FE-based MFTJs, and a TMR exceeding 6.8 × 10⁵%, enhanced by 2 orders of magnitude over typical MFTJs. These mechanisms resolve the performance trade-off in MFTJs, enabling six distinct nonvolatile resistance states at room temperature.

Light-induced magnetisation switching is one of the most intriguing and promising areas where an ultrafast phenomenon can be utilised in technological applications. So far, experiment and theory have considered the origin of all-optical helicity-independent magnetisation switching (AO-HIS) in individual magnetic films only as a microscopically local, thermally-driven process of angular momentum transfer between different subsystems. Here, we demonstrate that this local picture is insufficient and that AO-HIS must also be regarded as a spatially inhomogeneous process along the depth within a few-nanometre thin magnetic layer. Two regions of opposite magnetisation directions are observed, separated by a highly mobile boundary, which propagates along the depth of a 9.4 nm thin Gd₂₅Co₇₅ alloy. The dynamics of this transient boundary determines the final magnetisation state as well as the speed of AO-HIS throughout the entire magnetic layer. The ability to understand the influence of nanoscale and transient inhomogeneities on ultrafast switching phenomena and more generally on phase transitions will open new routes for material design and excitation scenarios in future devices for transferring and storing information.

All-optical switching (AOS) involves manipulating magnetization using only a pulsed laser, presenting a promising approach for next-generation magnetic recording devices. NiCo2O4 (NCO) thin films, a rare-earth-free ferrimagnetic oxide, exhibit a high Curie temperature and strong perpendicular magnetic anisotropy. This study demonstrates AOS in NCO thin films at room temperature using long-duration laser pulses and high repetition rates. Unlike previous findings, the AOS phenomena we report here are helicity-dependent and observable with an ultrashort pulsed laser. Consequently, two distinct types of AOS can be observed in a single NCO thin film, contingent on the characteristics of the laser pulses and temperature.

Single pulse All Optical Helicity-Independent Switching is demonstrated in an in-plane magnetized magnetic tunnel junction. A toggle switching of the 2 nm thick Co40Fe40B20 soft layer could be achieved by exchange coupling the Co40Fe40B20 with a 10 nm thick Co85Gd15 layer monitored by measuring the Tunnel magneto resistance of the device. The use of in plane magnetized electrodes relaxes the constrains linked to perpendicular magnetic anisotropy systems while achieving a tunneling magnetoresistance ratio exceeding 100%. The influence of the upper electrical electrode, which is opaque to the laser beam in this study, is also discussed.