Thickness and power dependence of the spin-pumping effect inY3Fe5O12/Pt heterostructures measured by the inverse spin Hall effect (original) (raw)
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We report the frequency dependence of the spin current emission (spin pumping) in a hybrid ferrimagnetic insulator/normal metal system as a function of the insulating layer thickness. The system is based on an yttrium iron garnet (YIG) film [0.2, 1, and 3 μm] grown by liquid-phase epitaxy coupled with a spin current detector of platinum[6 nm]. A strong YIG thickness dependence of the efficiency of the spin pumping has been observed. The highest conversion factor V /P abs has been demonstrated for the thinner YIG (1.79 and 0.55 mV/mW at 2.5 and 10 GHz, respectively), which is of interest for research heading towards YIG-based devices. Furthermore, we demonstrate the threshold frequency dependence of the three-magnon splitting process, which is shown to cease to exist for the thinner YIG of 0.2 μm.
Advanced electronic materials, 2016
include recently discovered phenomena such as the quantum anomalous Hall effect [2] in magnetic topological insulators (TIs), [3] spin transfer torque [4,5] effects in nonmagnetic metal/ferromagnetic metal/ oxide heterostructures, and spin orbit torque (SOT) effects in heterostructures that include ferromagnetic metals/heavy metals, [6,7] magnetically-doped TIs, [8] and FMI/heavy metals where the FMI is a garnet [9] or Ba hexaferrite. [10] To realize novel circuit devices based on these effects a variety of magnetic materials and heterostructures has still to be developed in which the magnetic properties and interfacial spin transport can be controlled. FMIs with PMA are of particular interest in spintronics. In FMI/heavy metal or FMI/TI heterostructures, current is limited to the metal or to the surface layer of the TI which reduces the conductivity (and potentially the power consumption) compared to all-metallic structures, and avoids the possibility of direct spin transfer torque from current flow in the FMI layer. This facilitates the study of proximity effects, SOT and other exotic phenomena occurring at the interfaces, enabling for example an identification of the various contributions to spin orbit torques. Moreover, the presence of PMA in the FMI leads to stray-field-induced interface effects even at remanence. Domain walls in PMA films also have qualitatively different structures and dynamics compared to those of FMIs with in-plane magnetic anisotropy, which is relevant to racetrack memory or logic devices. Thus there is considerable interest in developing PMA FMI materials and heterostructures. One of the most prominent classes of FMI is that of ferrimagnetic iron garnets, of which the best studied is Y 3 Fe 5 O 12 (YIG). The ultralow damping [11] and magneto-optical properties [12,13] of YIG are well known. The former makes YIG a suitable candidate for spin wave logic [14] and signal transmitters [15] due to the extremely large magnon propagation length of several tens of millimeters. YIG/heavy metal (e.g., Pt, W, Ta) and YIG/topological insulator heterostructures have demonstrated proximity effects, spin pumping, spin Seebeck, and other spintronic phenomena. [15-19] However, YIG films generally have an in-plane easy axis dominated by shape anisotropy due to their weak With recent developments in the field of spintronics, ferromagnetic insulator (FMI) thin films have emerged as an important component of spintronic devices. Ferrimagnetic yttrium iron garnet in particular is an excellent insulator with low Gilbert damping and a Curie temperature well above room temperature, and has been incorporated into heterostructures that exhibit a plethora of spintronic phenomena including spin pumping, spin Seebeck, and proximity effects. However, it has been a challenge to develop high quality sub-10 nm thickness FMI garnet films with perpendicular magnetic anisotropy (PMA) and PMA garnet/heavy metal heterostructures to facilitate advances in spin-current and anomalous Hall phenomena. Here, robust PMA in ultrathin thulium iron garnet (TmIG) films of high structural quality down to a thickness of 5.6 nm are demonstrated, which retain a saturation magnetization close to bulk. It is shown that TmIG/Pt bilayers exhibit a large spin Hall magnetoresistance (SMR) and SMR-driven anomalous Hall effect, which indicates efficient spin transmission across the TmIG/Pt interface. These measurements are used to quantify the interfacial spin mixing conductance in TmIG/Pt and the temperature-dependent PMA of the TmIG thin film.
Current-controlled magnon propagation in Pt/Y3Fe5O12 heterostructure
Applied Physics Letters, 2020
We present a dynamic spin wave (SW) modulation technique using direct current (DC) to manipulate the magnetic properties of an ultralow-damping Y 3 Fe 5 O 12 thin film. The microwave excitation and detection technique with two coplanar waveguide antenna arrangements on the Y 3 Fe 5 O 12 (YIG) surface is used to characterize the SW. An additional platinum (Pt) stripe connected to a current source is integrated between the coplanar waveguide pair to demonstrate the SW resonant frequency and amplitude modulation by current induction. We selected a Pt stripe due to its significantly lower spin wave absorption property. The application of current through the Pt stripe generates local joule heating that modifies the magnetic properties of the YIG film. Temperature variation through local heating modifies the saturation magnetization of the YIG film, which, in turn, modulates the SW frequency. Moreover, the amplitude of the SW spectra is found to be tuned by the current amplitude. This phenomenon is mainly described by magnon-magnon scattering induced by the spin Seebeck effect in the case of local heating. Furthermore, the group velocity of the proposed device is also found to be responsive to the current, which has been explained by both magnon-magnon and magnon-phonon scattering.
Crystal orientation dependent spin pumping in a Bi0.1Y2.9Fe5O12/Pt interface
Journal of Physics D, 2023
Ferromagnetic resonance (FMR) based spin pumping is a versatile tool to quantify the spin mixing conductance and spin to charge conversion (S2CC) efficiency of ferromagnet/normal metal (FM/NM) heterostructure. The spin mixing conductance of FM/NM interface can also be tuned by the crystal orientation symmetry of epitaxial FM. In this work, we study the S2CC in epitaxial Bismuth substituted Yttrium Iron Garnet (Bi0.1Y2.9Fe5O12) thin films Bi-YIG (100 nm) interfaced with heavy metal platinum (Pt (8 nm)) deposited by pulsed laser deposition process on different crystal orientation Gd3Ga5O12 (GGG) substrates i.e. [100] and [111]. The crystal structure and surface roughness characterized by X-Ray diffraction and atomic force microscopy measurements establish epitaxial Bi-YIG[100], Bi-YIG[111] orientations and atomically flat surfaces respectively. The S2CC quantification has been realized by two complimentary techniques, (i) FMR-based spin pumping and inverse spin Hall effect (ISHE) at GHz frequency and (ii) temperature dependent spin Seebeck measurements. FMR-ISHE results demonstrate that the [111] oriented Bi-YIG/Pt sample shows significantly higher values of spin mixing conductance ((2.31±0.23)10 18 m-2) and spin Hall angle (0.01±0.001) as compared to the [100] oriented Bi-YIG/Pt. A longitudinal spin Seebeck measurement reveals that the [111] oriented sample has higher spin Seebeck coefficient (106.40±10 nV mm-1 K-1). This anisotropic nature of spin mixing 2 conductance and spin Seebeck coefficient in [111] and [100] orientation has been discussed using the magnetic environment elongation along the surface normal or parallel to the growth direction. Our results aid in understanding the role of crystal orientation symmetry in S2CC based spintronics devices.
Physical Review B
The magnetic state of heavy metal Pt thin films in proximity to the ferrimagnetic insulator Y3Fe5O12 has been investigated systematically by means of x-ray magnetic circular dichroism and xray resonant magnetic reflectivity measurements combined with angle-dependent magnetotransport studies. To reveal intermixing effects as the possible cause for induced magnetic moments in Pt, we compare thin film heterostructures with different order of the layer stacking and different interface properties. For standard Pt layers on Y3Fe5O12 thin films, we do not detect any static magnetic polarization in Pt. These samples show an angle-dependent magnetoresistance behavior, which is consistent with the established spin Hall magnetoresistance. In contrast, for the inverted layer sequence, Y3Fe5O12 thin films grown on Pt layers, Pt displays a finite induced magnetic moment comparable to that of all-metallic Pt/Fe bilayers. This magnetic moment is found to originate from finite intermixing at the Y3Fe5O12/Pt interface. As a consequence, we found a complex angle-dependent magnetoresistance indicating a superposition of the spin Hall and the anisotropic magnetoresistance in these type of samples. Both effects can be disentangled from each other due to their different angle dependence and their characteristic temperature evolution.
Electrical Detection of Spin Backflow from an Antiferromagnetic Insulator/Y3Fe5O12 Interface
Physical Review Letters, 2017
Spin Hall magnetoresistance (SMR) has been observed in Pt/NiO/Y3Fe5O12 (YIG) heterostructures with characteristics very different from those in Pt/YIG. This phenomenon indicates that a spin current generated by the spin Hall effect in Pt transmits through the insulating NiO and is reflected from the NiO/YIG interface. The SMR in Pt/NiO/YIG shows a strong temperature dependence dominated by effective spin conductance, due to antiferromagnetic magnons and spin fluctuation. Inverted SMR has been observed below a temperature which increases with the NiO thickness, suggesting a spin-flip reflection from the antiferromagnetic NiO exchange coupled with the YIG.
Frequency and power dependence of spin-current emission by spin pumping in a thin-film YIG/Pt system
Physical Review B, 2012
This paper presents the frequency dependence of the spin-current emission by spin pumping in a hybrid ferrimagnetic insulator/normal metal system. The system is based on a ferrimagnetic insulating thin film of yttrium iron garnet (YIG, 200 nm) grown by liquid-phase epitaxy coupled with a normal metal with a strong spin-orbit coupling (Pt, 15 nm). The YIG layer presents an isotropic behavior of the magnetization in the plane, a small linewidth, and a roughness lower than 0.4 nm. Here we discuss how the voltage signal from the spin-current detector depends on the frequency (0.6-7 GHz), the microwave power, P in (1-70 mW), and the in-plane static magnetic field. A strong enhancement of the spin-current emission is observed at low frequencies, showing the appearance of nonlinear phenomena.
Spin wave modulation by topographical perturbation in Y3Fe5O12 thin films
AIP Advances, 2020
We present a comparison of the spin wave propagation in Au/Y 3 Fe5O 12 and Pt/Y 3 Fe5O 12 bilayers. Microwave technique with a coplanner waveguide arrangement was used to excite and detect the spin wave. We observed a suppression in the propagating spin wave intensity when a metal stripe is placed on the surface of Y 3 Fe5O 12 in the spin wave propagation path due to the spin pumping from Y 3 Fe5O 12 to nonmagnetic metal stripe. However, a significant difference in the suppression property was observed with the Au and Pt electrode layers, which cannot be explained by the enhancement of the damping constant induced by spin pumping alone. The significant suppression of the spin wave propagation in the Au/Y 3 Fe5O 12 bilayer system is attributed to the spin backflow and two magnon scattering.
Tm3 Fe5 O12 /Pt Heterostructures with Perpendicular Magnetic Anisotropy for Spintronic Applications
Advanced Electronic Materials, 2016
include recently discovered phenomena such as the quantum anomalous Hall effect [2] in magnetic topological insulators (TIs), [3] spin transfer torque [4,5] effects in nonmagnetic metal/ferromagnetic metal/ oxide heterostructures, and spin orbit torque (SOT) effects in heterostructures that include ferromagnetic metals/heavy metals, [6,7] magnetically-doped TIs, [8] and FMI/heavy metals where the FMI is a garnet [9] or Ba hexaferrite. [10] To realize novel circuit devices based on these effects a variety of magnetic materials and heterostructures has still to be developed in which the magnetic properties and interfacial spin transport can be controlled. FMIs with PMA are of particular interest in spintronics. In FMI/heavy metal or FMI/TI heterostructures, current is limited to the metal or to the surface layer of the TI which reduces the conductivity (and potentially the power consumption) compared to all-metallic structures, and avoids the possibility of direct spin transfer torque from current flow in the FMI layer. This facilitates the study of proximity effects, SOT and other exotic phenomena occurring at the interfaces, enabling for example an identification of the various contributions to spin orbit torques. Moreover, the presence of PMA in the FMI leads to stray-field-induced interface effects even at remanence. Domain walls in PMA films also have qualitatively different structures and dynamics compared to those of FMIs with in-plane magnetic anisotropy, which is relevant to racetrack memory or logic devices. Thus there is considerable interest in developing PMA FMI materials and heterostructures. One of the most prominent classes of FMI is that of ferrimagnetic iron garnets, of which the best studied is Y 3 Fe 5 O 12 (YIG). The ultralow damping [11] and magneto-optical properties [12,13] of YIG are well known. The former makes YIG a suitable candidate for spin wave logic [14] and signal transmitters [15] due to the extremely large magnon propagation length of several tens of millimeters. YIG/heavy metal (e.g., Pt, W, Ta) and YIG/topological insulator heterostructures have demonstrated proximity effects, spin pumping, spin Seebeck, and other spintronic phenomena. [15-19] However, YIG films generally have an in-plane easy axis dominated by shape anisotropy due to their weak With recent developments in the field of spintronics, ferromagnetic insulator (FMI) thin films have emerged as an important component of spintronic devices. Ferrimagnetic yttrium iron garnet in particular is an excellent insulator with low Gilbert damping and a Curie temperature well above room temperature, and has been incorporated into heterostructures that exhibit a plethora of spintronic phenomena including spin pumping, spin Seebeck, and proximity effects. However, it has been a challenge to develop high quality sub-10 nm thickness FMI garnet films with perpendicular magnetic anisotropy (PMA) and PMA garnet/heavy metal heterostructures to facilitate advances in spin-current and anomalous Hall phenomena. Here, robust PMA in ultrathin thulium iron garnet (TmIG) films of high structural quality down to a thickness of 5.6 nm are demonstrated, which retain a saturation magnetization close to bulk. It is shown that TmIG/Pt bilayers exhibit a large spin Hall magnetoresistance (SMR) and SMR-driven anomalous Hall effect, which indicates efficient spin transmission across the TmIG/Pt interface. These measurements are used to quantify the interfacial spin mixing conductance in TmIG/Pt and the temperature-dependent PMA of the TmIG thin film.