arXiv subjects

Rembert Duine

Publications and source records attributed to Rembert Duine.

7 recordsLinked to original sources

arXiv2025

Exciting terahertz magnons with amplitude modulated light: spin pumping, squeezed states, symmetry breaking and pattern formation

We show how amplitude modulated, coherent high-frequency drives can be used to access otherwise difficult to reach collective resonances and off-resonantly induce parametric instabilities. In particular, we demonstrate that difficult to access antiferromagnetic resonances in the THz range can be parametrically excited with signals at optical frequencies via a mechanism that we call Modulated Floquet Parametric Driving (MFPD). We study spin pumping and the formation of entangled, two-mode squeezed magnon pairs in anisotropic antiferromagnets under MFPD. Furthermore, we show that MFPD induces transitions to symmetry breaking steady-states in which dynamical spin patterns are formed by resonant magnon pairs.

cond-mat.mes-hall↗

arXiv2024

Entropic magnetic interlayer coupling

Nanomagnetism concerns the engineering of magnetic interactions in heterostructures that consist of layers of magnetic and non-magnetic materials. Mostly, these interactions are dominated by the minimization of energy. Here, we propose an effective magnetic interlayer coupling that is dominated by the maximization of entropy. As an example, we consider the system that mediates the effective interactions to be square spin ice, in which case we find purely entropic interactions that are long-ranged. We argue that in the thermodynamic limit the entropic interlayer coupling gives rise to entropic torques on the magnetization direction. For small systems, the physical properties are well characterized by the mutual information between the two magnets that are coupled. Because entropic interactions become stronger for higher temperatures, our findings may benefit the development of nanomagnetic devices that require thermal stability.

cond-mat.mes-hall↗

arXiv2023

Bath-induced spin inertia

Spin dynamics is usually described as massless or, more precisely, as free of inertia. Recent experiments, however, found direct evidence for inertial spin dynamics. In turn, it is necessary to rethink the basics of spin dynamics. Focusing on a macrospin in an environment (bath), we show that the spin-to-bath coupling gives rise to spin inertia. This bath-induced spin inertia appears universally from all the high-frequency bath modes. We expect our results to provide new insights into recent experiments on spin inertia. Moreover, they indicate that any channel for spin dissipation should also be accompanied by a term accounting for bath-induced spin inertia. As an illustrative example, we consider phonon-bath-induced spin inertia in a YIG/GGG stack.

cond-mat.mes-hall↗

arXiv2022

Spin-polarized hot electron transport versus spin pumping mediated by local heating

A `toy model' - aimed at capturing the essential physics - is presented that jointly describes spin-polarized hot electron transport and spin pumping driven by local heating. These two processes both contribute to spin-current generation in laser-excited magnetic heterostructures. The model is used to compare the two contributions directly. The spin-polarized hot electron current is modeled as one generation of hot electrons with a spin-dependent excitation and relaxation scheme. Upon decay, the excess energy of the hot electrons is transferred to a thermalized electron bath. The elevated electron temperature leads to an increased rate of electron-magnon scattering processes and yields a local accumulation of spin. This process is dubbed as spin pumping by local heating. The built-up spin accumulation is effectively driven out of the ferromagnetic system by (interfacial) electron transport. Within our model, the injected spin current is dominated by the contribution resulting from spin pumping, while the hot electron spin current remains relatively small. We derive that this observation is related to the ratio between the Fermi temperature and Curie temperature, and we show what other fundamental parameters play a role.

cond-mat.mes-hall↗

arXiv2021

Propagation length of antiferromagnetic magnons governed by domain configurations

The compensated magnetic order and characteristic, terahertz frequencies of antiferromagnetic materials makes them promising candidates to develop a new class of robust, ultra-fast spintronic devices. The manipulation of antiferromagnetic spin-waves in thin films is anticipated to lead to new exotic phenomena such as spin-superfluidity, requiring an efficient propagation of spin-waves in thin films. However, the reported decay length in thin films has so far been limited to a few nanometers. In this work, we achieve efficient spin-wave propagation, over micrometer distances, in thin films of the insulating antiferromagnet hematite with large magnetic domains whilst evidencing much shorter attenuation lengths in multidomain thin films. Through transport and magnetic imaging, we conclude on the role of the magnetic domain structure and spin-wave scattering at domain walls to govern the transport. We manipulate the spin transport by tailoring the domain configuration through field cycle training. For the appropriate crystalline orientation, zero-field spin-transport is achieved across micrometers, as required for device integration.

cond-mat.mtrl-sci↗

arXiv2019

Anisotropies and magnetic phase transitions in insulating antiferromagnets determined by a Spin-Hall magnetoresistance probe

We demonstrate that we can determine the antiferromagnetic anisotropies and the bulk Dzyaloshinskii-Moriya fields of the insulating iron oxide hematite, α-Fe2O3, using a surface sensitive spin-Hall magnetoresistance (SMR) technique. We develop an analytical model that in combination with SMR measurements, allow for the identification of the material parameters of this prototypical antiferromagnet over a wide range of temperatures and magnetic field values. Using devices with different orientations, we demonstrate that the SMR response strongly depends on the direction of the charge current with respect to the magneto-crystalline anisotropies axis. We show that we can extract the anisotropies over a wide temperature range including across the Morin phase transition. We observe that the electrical response is dominated by the orientation of the antiferromagnetic Néel order parameter, rather than by the emergent weak magnetic moment. Our results highlight that the surface sensitivity of the SMR allows accessing the magnetic anisotropies of antiferromagnetic crystals and in particular thin films where other methods to determine anisotropies such as bulk-sensitive magnetic susceptibility measurements do not provide sufficient sensitivity.

cond-mat.mes-hall↗

arXiv2015

Asymmetric magnetic bubble expansion under in-plane field in Pt/Co/Pt: effect of interface engineering

We analyse the impact of growth conditions on asymmetric magnetic bubble expansion under in-plane field in ultrathin Pt / Co / Pt films. Specifically, using sputter deposition we vary the Ar pressure during the growth of the top Pt layer. This induces a large change in the interfacial structure as evidenced by a factor three change in the effective perpendicular magnetic anisotropy. Strikingly, a discrepancy between the current theory for domain-wall propagation based on a simple domain-wall energy density and our experimental results is found. This calls for further theoretical development of domain-wall creep under in-plane fields and varying structural asymmetry.

cond-mat.mes-hall↗