Static magnetic proximity effects and spin Hall magnetoresistance in Pt/Y3Fe5O12 and inverted Y3Fe5O12/Pt bilayers (original) (raw)
Related papers
Interface-induced spin Hall magnetoresistance enhancement in Pt-based tri-layer structure
Scientific Reports, 2018
In this study, we integrated bilayer structure of covered Pt on nickel zinc ferrite (NZFO) and CoFe/Pt/ NZFO tri-layer structure by pulsed laser deposition system for a spin Hall magnetoresistance (SMR) study. In the bilayer structure, the angular-dependent magnetoresistance (MR) results indicate that Pt/NZFO has a well-defined SMR behavior. Moreover, the spin Hall angle and the spin diffusion length, which were 0.0648 and 1.31 nm, respectively, can be fitted by changing the Pt thickness in the longitudinal SMR function. Particularly, the MR ratio of the bilayer structure (Pt/NZFO) has the highest changing ratio (about 0.135%), compared to the prototype structure Pt/Y 3 Fe 5 O 12 (YIG) because the NZFO has higher magnetization. Meanwhile, the tri-layer samples (CoFe/Pt/NZFO) indicate that the MR behavior is related with CoFe thickness as revealed in angular-dependent MR measurement. Additionally, comparison between the tri-layer structure with Pt/NZFO and CoFe/Pt bilayer systems suggests that the SMR ratio can be enhanced by more than 70%, indicating that additional spin current should be injected into Pt layer.
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.
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.
Physical Review B, 2015
The dependence of the spin-pumping effect on the yttrium iron garnet (Y3Fe5O12, YIG) thickness detected by the inverse spin Hall effect (ISHE) has been investigated quantitatively. Due to the spinpumping effect driven by the magnetization precession in the ferrimagnetic insulator Y3Fe5O12 film a spin-polarized electron current is injected into the Pt layer. This spin current is transformed into electrical charge current by means of the ISHE. An increase of the ISHE-voltage with increasing film thickness is observed and compared to the theoretically expected behavior. The effective damping parameter of the YIG/Pt samples is found to be enhanced with decreasing Y3Fe5O12 film thickness. The investigated samples exhibit a spin mixing conductance of g ↑↓ eff = (3.87±0.21)×10 18 m −2 and a spin Hall angle between θISHE = 0.013 ± 0.001 and 0.045 ± 0.004 depending on the used spindiffusion length. Furthermore, the influence of nonlinear effects on the generated voltage and on the Gilbert damping parameter at high excitation powers are revealed. It is shown that for small YIG film thicknesses a broadening of the linewidth due to nonlinear effects at high excitation powers is suppressed because of a lack of nonlinear multi-magnon scattering channels. We have found that the variation of the spin-pumping efficiency for thick YIG samples exhibiting pronounced nonlinear effects is much smaller than the nonlinear enhancement of the damping.
Exchange magnetic field torques in YIG/Pt bilayers observed by the spin-Hall magnetoresistance
Applied Physics Letters, 2013
The effective field torque of an yttrium-iron-garnet (YIG) film on the spin accumulation in an attached platinum (Pt) film is measured by the spin-Hall magnetoresistance (SMR). As a result, the magnetization direction of a ferromagnetic insulating layer can be measured electrically. Experimental transverse and longitudinal resistances are well described by the theoretical model of SMR in terms of the direct and inverse spin-Hall effect, for different Pt thicknesses [3, 4, 8, and 35 nm]. Adopting a spin-Hall angle of Pt h SH ¼ 0:08, we obtain the spin diffusion length of Pt (k ¼ 1:1 6 0:3 nm) as well as the real (G r ¼ ð7 6 3Þ Â 10 14 X À1 m À2 ) and imaginary part (G i ¼ ð5 6 3Þ Â 10 13 X À1 m À2 ) of the spin-mixing conductance and their ratio (G r =G i ¼ 16 6 4).
Journal of Magnetism and Magnetic Materials, 2018
The spin Hall magnetoresistance effects (SMR) in four heterostructures consist of different boundaries of Pt layer has been investigated. The result in this work shows that the two boundaries of Pt layer in all heterostructures both influence the spin current absorption and reflection. The Pt/air interface would weaken the spin current absorption at the Co 2 FeSi/Pt interface on the other side of the Pt layer. On the contrary, the Pt/MgO(0 0 1) interface could boost the spin current absorption strongly at the Co 2 FeSi/Pt interface on the other side of the Pt layer. And this promotion effect is much stronger than the Co 2 FeSi/Pt interface on the spin current absorption at the other Co 2 FeSi/Pt interface. The MgO capping layer may avoid anisotropic magnetoresistance (AMR) induced SMR ratio decreasing at low temperature. This study provides a new way for modulating spin current absorption at the FM/HM interface.
ACS Appl. Mater. Interfaces, 2018
Pure spin currents have potential for use in energy-friendly spintronics. They can be generated by a flow of charge along a nonmagnetic metal with large spin−orbit coupling. This produces a spin accumulation at the surfaces, controllable by the magnetization of an adjacent ferromagnetic layer. Paramagnetic metals typically used are close to ferromagnetic instability and thus magnetic proximity effects can contribute to the observed angular-dependent magnetoresistance (ADMR). As interface phenomena govern the spin conductance across the metal/ferromagnetic−insulator heterostructures, unraveling these distinct contributions is pivotal for a full understanding of spin current conductance. Here, we report X-ray absorption and magnetic circular dichroism (XMCD) at Pt M and (Co, Fe) L absorption edges and atomically resolved energy electron loss spectroscopy (EELS) data of Pt/CoFe 2 O 4 bilayers, where CoFe 2 O 4 layers have been capped by Pt grown at different temperatures. It was found that the ADMR differs dramatically, dominated either by spin Hall magnetoresistance (SMR) associated with the spin Hall effect or by anisotropic magnetoresistance. The XMCD and EELS data indicate that the Pt layer grown at room temperature does not display any magnetic moment, whereas when grown at a higher temperature, it becomes magnetic due to interfacial Pt-(Co, Fe) alloying. These results enable differentiation of spin accumulation from interfacial chemical reconstructions and tailoring of the angular-dependent magnetoresistance.
arXiv (Cornell University), 2023
In this study, we investigate the dynamic response of a Y 3 Fe 5 O 12 (YIG)/ Gd 3 Fe 5 O 12 (GdIG)/ Pt trilayer system by measurements of the ferromagnetic resonance (FMR) and the resulting pumped spin current detected by the inverse spin Hall effect. This trilayer system offers the unique opportunity to investigate the spin dynamics of the ferrimagnetic GdIG, close to its compensation temperature. We show that our trilayer acts as a highly tunable spin current source. Our experimental results are corroborated by micro-magnetic simulations. As the detected spin current in the top Pt layer is distinctly dominated by the GdIG layer, this gives the unique opportunity to investigate the excitation and dynamic properties of GdIG while comparing it to the broadband FMR absorption spectrum of the heterostructure.