Impact of electromagnetic fields and heat on spin transport signals in Y$_{3}$Fe$_{5}$O$_{12}$

Exploring new strategies to perform magnon logic is a key requirement for the further development of magnon-based spintronics. In this work, we realize a three-terminal magnon transport device to study the possibility of manipulating magnonic spin information transfer in a magnetic insulator via localized magnetic fields and heat generation. The device comprises two parallel Pt wires as well as a Cu center wire that are deposited on the ferrimagnetic insulator Y$_{3}$Fe$_{5}$O$_{12}$. While the Pt wires act as spin current injector and detector, the Cu wire is used to create local magnetostatic fields and additional heat, which impact both the magnetic configuration and the magnons within t…

Interfacial Dzyaloshinskii-Moriya interaction and chiral magnetic textures in a ferrimagnetic insulator

The interfacial Dzyaloshinskii-Moriya interaction (DMI) in multilayers of heavy metal and ferromagnetic metals enables the stabilization of novel chiral spin structures such as skyrmions. Magnetic insulators, on the other hand can exhibit enhanced dynamics and properties such as lower magnetic damping and therefore it is of interest to combine the properties enabled by interfacial DMI with insulating systems. Here, we demonstrate the presence of interfacial DMI in heterostructures that include insulating magnetic layers. We use a bilayer of perpendicularly magnetized insulating thulium iron garnet (TmIG) and the heavy metal platinum, and find a surprisingly strong interfacial DMI that, comb…

Control of the coupling strength and linewidth of a cavity magnon-polariton

The full coherent control of hybridized systems such as strongly coupled cavity photon-magnon states is a crucial step to enable future information processing technologies. Thus, it is particularly interesting to engineer deliberate control mechanisms such as the full control of the coupling strength as a measure for coherent information exchange. In this work, we employ cavity resonator spectroscopy to demonstrate the complete control of the coupling strength of hybridized cavity photon-magnon states. For this, we use two driving microwave inputs which can be tuned at will. Here, only the first input couples directly to the cavity resonator photons, whilst the second tone exclusively acts …

Structural sensitivity of the spin Hall magnetoresistance in antiferromagnetic thin films

A. Ross and M.K. acknowledge support from the Graduate School of Excellence Materials Science in Mainz (Grant No.DFG/GSC 266). This work was supported by the Max Planck Graduate Center with the Johannes Gutenberg-Universitat Mainz (MPGC). A. Ross, R.L., and M.K. acknowledge support from the DFG Projects No. 423441604 and No. 403502522. R.L. acknowledges the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie Grant Agreement FAST No. 752195. All authors from Mainz also acknowledge support from both MaHoJeRo (DAAD Spintronics network, Project No. 57334897), SPIN+X (DFG SFB TRR 173, Project No. A01) and KAUST (Grant No. OSR-2019-CRG8-4048.2). D.A.G.…

Orientation-dependent direct and inverse spin Hall effects in Co 60 Fe 20 B 20

Efficient spin torques in antiferromagnetic CoO/Pt quantified by comparing field- and current- induced switching

Comment: 16 pages (manuscript and supplementary), 12 figures

Tunable long-distance spin transport in a crystalline antiferromagnetic iron oxide.

Spintronics relies on the transport of spins, the intrinsic angular momentum of electrons, as an alternative to the transport of electron charge as in conventional electronics. The long-term goal of spintronics research is to develop spin-based, low-dissipation computing-technology devices. Recently, long-distance transport of a spin current was demonstrated across ferromagnetic insulators1. However, antiferromagnetically ordered materials, the most common class of magnetic materials, have several crucial advantages over ferromagnetic systems for spintronics applications2: antiferromagnets have no net magnetic moment, making them stable and impervious to external fields, and can be operated…

Impact of electromagnetic fields and heat on spin transport signals in Y3Fe5O12

Exploring new strategies to perform magnon logic is a key requirement for the further development of magnon-based spintronics. In this paper, we realize a three-terminal magnon transport device to study the possibility of manipulating magnonic spin information transfer in a magnetic insulator via localized magnetic fields and heat generation. The device comprises two parallel Pt wires as well as a Cu center wire that are deposited on the ferrimagnetic insulator ${\mathrm{Y}}_{3}{\mathrm{Fe}}_{5}{\mathrm{O}}_{12}$. While the Pt wires act as spin current injector and detector, the Cu wire is used to create local magnetostatic fields and additional heat, which impact both the magnetic configur…

Mechanism of Néel Order Switching in Antiferromagnetic Thin Films Revealed by Magnetotransport and Direct Imaging.

We probe the current-induced magnetic switching of insulating antiferromagnet/heavy metals systems, by electrical spin Hall magnetoresistance measurements and direct imaging, identifying a reversal occurring by domain wall (DW) motion. We observe switching of more than one third of the antiferromagnetic domains by the application of current pulses. Our data reveal two different magnetic switching mechanisms leading together to an efficient switching, namely the spin-current induced effective magnetic anisotropy variation and the action of the spin torque on the DWs.

Propagation Length of Antiferromagnetic Magnons Governed by Domain Configurations.

Spintronics seeks to functionalize antiferromagnetic materials to develop memory and logic devices operating at terahertz speed and robust against external magnetic field perturbations. To be useful, such functionality needs to be developed in thin film devices. The key functionality of long-distance spin-transport has, however, so far only been reported in bulk single crystal antiferromagnets, while in thin films, transport has so far been limited to a few nanometers. In this work, we electrically achieve a long-distance propagation of spin-information in thin films of the insulating antiferromagnet hematite. Through transport and magnetic imaging, we demonstrate a strong correlation betwe…

An insulating doped antiferromagnet with low magnetic symmetry as a room temperature spin conduit

We report room temperature long-distance spin transport of magnons in antiferromagnetic thin film hematite doped with Zn. The additional dopants significantly alter the magnetic anisotropies, resulting in a complex equilibrium spin structure that is capable of efficiently transporting spin angular momentum at room temperature without the need for a well-defined, pure easy-axis or easy-plane anisotropy. We find intrinsic magnon spin-diffusion lengths of up to 1.5 {\mu}m, and magnetic domain governed decay lengths of 175 nm for the low frequency magnons, through electrical transport measurements demonstrating that the introduction of non-magnetic dopants does not strongly reduce the transport…

Electrical detection of the spin reorientation transition in antiferromagnetic TmFeO3 thin films by spin Hall magnetoresistance

TmFeO$_3$ (TFO) is a canted antiferromagnet that undergoes a spin reorientation transition (SRT) with temperature between 82 K and 94 K in single crystals. In this temperature region, the N\'eel vector continuously rotates from the crystallographic $c$-axis (below 82 K) to the $a$-axis (above 94 K). The SRT allows for a temperature control of distinct antiferromagnetic states without the need for a magnetic field, making it apt for applications working at THz frequencies. For device applications, thin films of TFO are required as well as an electrical technique for reading out the magnetic state. Here we demonstrate that orthorhombic TFO thin films can be grown by pulsed laser deposition an…

Spin structure and spin Hall magnetoresistance of epitaxial thin films of the insulating non-collinear antiferromagnet SmFeO3

We report a combined study of imaging the antiferromagnetic (AFM) spin structure and measuring the spin Hall magnetoresistance (SMR) in epitaxial thin films of the insulating non-collinear antiferromagnet SmFeO$_3$. X-ray magnetic linear dichroism photoemission electron microscopy measurements reveal that the AFM spins of the SmFeO$_3$(110) align in the plane of the film. Angularly dependent magnetoresistance measurements show that SmFeO$_3$/Ta bilayers exhibit a positive SMR, in contrast to the negative SMR expected in previously studied collinear AFMs. The SMR amplitude increases linearly with increasing external magnetic field at higher magnetic field, suggesting that field-induced canti…

Scaling up electrically synchronized spin torque oscillator networks

AbstractSynchronized nonlinear oscillators networks are at the core of numerous families of applications including phased array wave generators and neuromorphic pattern matching systems. In these devices, stable synchronization between large numbers of nanoscale oscillators is a key issue that remains to be demonstrated. Here, we show experimentally that synchronized spin-torque oscillator networks can be scaled up. By increasing the number of synchronized oscillators up to eight, we obtain that the emitted power and the quality factor increase linearly with the number of oscillators. Even more importantly, we demonstrate that the stability of synchronization in time exceeds 1.6 millisecond…

Effective strain manipulation of the antiferromagnetic state of polycrystalline NiO

As a candidate material for applications such as magnetic memory, polycrystalline antiferromagnets offer the same robustness to external magnetic fields, THz spin dynamics, and lack of stray field as their single crystalline counterparts, but without the limitation of epitaxial growth and lattice matched substrates. Here, we first report the detection of the average Neel vector orientiation in polycrystalline NiO via spin Hall magnetoresistance (SMR). Secondly, by applying strain through a piezo-electric substrate, we reduce the critical magnetic field required to reach a saturation of the SMR signal, indicating a change of the anisotropy. Our results are consistent with polycrystalline NiO…

Exceptional sign changes of the nonlocal spin Seebeck effect in antiferromagnetic hematite

A.R. and M.K. acknowledge support from the Graduate School of Excellence Materials Science in Mainz (DFG/GSC 266). A.R. and M.K. also acknowledge support from both MaHoJeRo (DAAD Spintronics network, Projects No. 57334897 and No. 57524834) and SPIN+X (DFG SFB TRR 173, No. 268565370 Projects No. A01 and No. B02) and KAUST (Project No. OSR-2019-CRG8-4048.2). This work was supported by the Max Planck Graduate Center with the Johannes Gutenberg-Universitat Mainz (MPGC). A.R., R.L., M.E., U.N., and M.K. acknowledge support from the DFG Project No. 423441604. R.L. acknowledges the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie Grant Agreement FAST…

Orientation-dependent direct and inverse spin Hall effects in Co60Fe20B20

The spin Hall effect is a key element of various spintronics applications. Here, the authors study the orientation-dependent interconversion of spin and charge information in Co${}_{60}$Fe${}_{20}$B${}_{20}$. In a nonlocal magnon transport using Y${}_{3}$Fe${}_{5}$O${}_{12}$ as a spin conduit, the spin Hall effect amplitude depends on the relative alignment between the Y${}_{3}$Fe${}_{5}$O${}_{12}$ and Co${}_{60}$Fe${}_{20}$B${}_{20}$ magnetization vectors. In order to suppress direct magnonic contributions so as to study the electronic origin of this effect, Y${}_{3}$Fe${}_{5}$O${}_{12}$ and Co${}_{60}$Fe${}_{20}$B${}_{20}$ are exchange-decoupled by a Cu interlayer.

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

Antiferromagnets possess a number of intriguing and promising properties for electronic devices, which include a vanishing net magnetic moment and thus insensitivity to large magnetic fields and characteristic terahertz frequency dynamics. However, probing the antiferromagnetic ordering is challenging without synchrotron-based facilities. Here, we determine the material parameters of the insulating iron oxide hematite, α-Fe2O3, using the surface sensitive spin-Hall magnetoresistance (SMR). Combined with a simple analytical model, we extract the antiferromagnetic anisotropies and the bulk Dzyaloshinskii-Moriya field over a wide range of temperatures and magnetic fields. Across the Morin phas…

Magnon transport in the presence of antisymmetric exchange in a weak antiferromagnet

The Dzyaloshinskii-Moriya interaction (DMI) is at the heart of many modern developments in the research field of spintronics. DMI is known to generate noncollinear magnetic textures, and can take two forms in antiferromagnets: homogeneous or inter-sublattice, leading to small, canted moments and inhomogeneous or intra-sublattice, leading to formation of chiral structures. In this work, we first determine the strength of the effective field created by the DMI, using SQUID based magnetometry and transport measurements, in thin films of the antiferromagnetic iron oxide hematite, $\alpha$-Fe$_2$O$_3$. We demonstrate that DMI additionally introduces reconfigurability in the long distance magnon …

Spin structure and spin Hall magnetoresistance of epitaxial thin films of the insulating non-collinear antiferromagnet SmFeO 3

We report a combined study of imaging the antiferromagnetic (AFM) spin structure and measuring the spin Hall magnetoresistance (SMR) in epitaxial thin films of the insulating non-collinear antiferromagnet SmFeO3. X-ray magnetic linear dichroism photoemission electron microscopy measurements reveal that the AFM spins of the SmFeO3(1 1 0) align in the plane of the film. Angularly dependent magnetoresistance measurements show that SmFeO3/Ta bilayers exhibit a positive SMR, in contrast to the negative SMR expected in previously studied collinear AFMs. The SMR amplitude increases linearly with increasing external magnetic field at higher magnetic fields, suggesting that field-induced canting of …

Impact of electromagnetic fields and heat on spin transport signals in Y 3 Fe 5 O 12

Concurrent magneto-optical imaging and magneto-transport readout of electrical switching of insulating antiferromagnetic thin films

We demonstrate stable and reversible current induced switching of large-area ($> 100\;��m^2$) antiferromagnetic domains in NiO/Pt by performing concurrent transport and magneto-optical imaging measurements in an adapted Kerr microscope. By correlating the magnetic images of the antiferromagnetic domain changes and magneto-transport signal response in these current-induced switching experiments, we disentangle magnetic and non-magnetic contributions to the transport signal. Our table-top approach establishes a robust procedure to subtract the non-magnetic contributions in the transport signal and extract the spin-Hall magnetoresistance response associated with the switching of the antifer…

Gilbert damping of CoFe-alloys

We report structural, magnetic and dynamic properties of polycrystalline Coalt;subagt;xalt;/subagt;Fealt;subagt;1-xalt;/subagt;-alloy films on Sapphire, Silicon and MgO substrates across the full composition range, by using a Vector Network Analyser ferromagnetic resonance measurement technique (VNA-FMR), Superconducting Quantum Interference Device magnetometry (SQUID) and X-Ray Diffraction (XRD). In the approximate vicinity of 28% Co, we observe a minimum of the damping parameter, associated with a reduction in the density of states to a minimum value at the Fermi energy level. For films on all substrates, we find magnetic damping of the order of 4-5⋅10alt;supagt;-3alt;/supagt;, showing th…

Efficient Spin Torques in Antiferromagnetic CoO/Pt Quantified by Comparing Field- and Current-Induced Switching

We achieve current-induced switching in collinear insulating antiferromagnetic CoO/Pt, with fourfold in-plane magnetic anisotropy. This is measured electrically by spin Hall magnetoresistance and confirmed by the magnetic field-induced spin-flop transition of the CoO layer. By applying current pulses and magnetic fields, we quantify the efficiency of the acting current-induced torques and estimate a current-field equivalence ratio of 4×10^{-11}  T A^{-1} m^{2}. The Neel vector final state (n⊥j) is in line with a thermomagnetoelastic switching mechanism for a negative magnetoelastic constant of the CoO.

Electrical detection of the spin reorientation transition in antiferromagnetic TmFeO3 thin films by spin Hall magnetoresistance

$\mathrm{Tm}\mathrm{Fe}{\mathrm{O}}_{3}$ (TFO) is a canted antiferromagnet that undergoes a spin reorientation transition (SRT) with temperature between 82 and 94 K in single crystals. In this temperature region, the N\'eel vector continuously rotates from the crystallographic $c$ axis (below 82 K) to the $a$ axis (above 94 K). The SRT allows for a temperature control of distinct antiferromagnetic states without the need for a magnetic field, making it apt for applications working at terahertz frequencies. For device applications, thin films of TFO are required as well as an electrical technique for read-out of the magnetic state. Here, we demonstrate that orthorhombic TFO thin films can be…

Room temperature antiferromagnetic resonance and inverse spin-Hall voltage in canted antiferromagnets

We study theoretically and experimentally the spin pumping signals induced by the resonance of canted antiferromagnets with Dzyaloshinskii-Moriya interaction and demonstrate that they can generate easily observable inverse spin-Hall voltages. Using a bilayer of hematite/heavy metal as a model system, we measure at room temperature the antiferromagnetic resonance and an associated inverse spin-Hall voltage, as large as in collinear antiferromagnets. As expected for coherent spin pumping, we observe that the sign of the inverse spin-Hall voltage provides direct information about the mode handedness as deduced by comparing hematite, chromium oxide and the ferrimagnet yttrium-iron garnet. Our r…

Long-distance spin-transport across the Morin phase transition up to room temperature in ultra-low damping single crystals of the antiferromagnet α-Fe2O3

Antiferromagnetic materials can host spin-waves with polarizations ranging from circular to linear depending on their magnetic anisotropies. Until now, only easy-axis anisotropy antiferromagnets with circularly polarized spin-waves were reported to carry spin-information over long distances of micrometers. In this article, we report long-distance spin-transport in the easy-plane canted antiferromagnetic phase of hematite and at room temperature, where the linearly polarized magnons are not intuitively expected to carry spin. We demonstrate that the spin-transport signal decreases continuously through the easy-axis to easy-plane Morin transition, and persists in the easy-plane phase through …

Orientation-dependent direct and inverse spin Hall effects in Co60Fe20B20

Data for the article "Long-distance spin-transport across the Morin phase transition up to room temperature in the ultra-low damping alpha-Fe2O3 antiferromagnet"

Data for experimental magneto-transport and resonance measurements for the article " Long-distance spin-transport across the Morin phase transition up to room temperature in the ultra-low damping α-Fe2O3 antiferromagnet " (https://arxiv.org/abs/2005.14414)

Data of the article "Efficient spin torques in antiferromagnetic CoO/Pt quantified by comparing field- and current- induced switching"

Data for experimental transport measurements and analytical calculations for the article "Efficient spin torques in antiferromagnetic CoO/Pt quantified by comparing field- and current- induced switching" (https://arxiv.org/abs/2003.05923)

Data for the article "An insulating doped antiferromagnet with low magnetic symmetry as a room temperature spin conduit "

Data for the article "An insulating doped antiferromagnet with low magnetic symmetry as a room temperature spin conduit " (https://aip.scitation.org/doi/full/10.1063/5.0032940 and https://arxiv.org/abs/2011.09755)

Data for the article "Concurrent magneto-optical imaging and magneto-transport readout of electrical switching of insulating antiferromagnetic thin films"

Data for experimental transport measurements and optical imaging for the article "Concurrent magneto-optical imaging and magneto-transport readout of electrical switching of insulating antiferromagnetic thin films" (https://arxiv.org/abs/2004.13374).